A Multi-wavelength Studyon the X-ray Emissions
from Young Stellar Objects
in Orion Molecular Cloud 2 and 3
Masahiro Tsujimoto
Department of Physics, Graduate School of Science, Kyoto University
Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japantsujimot@cr.scphys.kyoto-u.ac.jp

Thesis submitted to the Department of Physics,
Graduate School of Science, Kyoto University
on January 6, 2003
in partial fulfillment of the requirements
for the degree of Doctor of Philosophy in physics

2

Abstract
We made a multi-wavelength study to reveal the variety and to understand the mechanisms of
X-ray emissions from young stellar objects (YSOs), selecting Orion molecular cloud (OMC)
2 and 3 as our study field. OMC-2 and OMC-3 are intermediate mass star-forming regions,which contain YSOs at all evolutional classes from class 0 protostars to T Tauri stars in awide range of mass from early-type stars to brown dwarfs.
We conducted deep observations on OMC-2 and OMC-3 in the X-ray and near-infrared(NIR) band respectively using the Chandra X-ray Observatory and the University of Hawaii
88 inch (2.2 m) telescope. In the X-ray band, we detected 385 sources in the Advanced
CCD Imaging Spectrometer (ACIS)-I image of 17×17 arcmin2 , which is complete down to
FX ∼ 10−14.5 ergs s−1 cm−2 with the faintest detected source of FX ∼ 10−15.5 ergs s−1 cm−2 inthe 0.5–8.0 keV energy range. In the NIR band, we obtained the J - (1.2 µm), H - (1.6 µm),
and K -band (2.2 µm) Quick Infrared Camera (QUIRC) images to extract 1448 NIR sourcesin a 512 arcmin2 region. The survey is complete down to J ∼ 17.5, H ∼ 16.5, and K ∼16.0 mag, matching well with the Chandra limit.
Combining the 2MASS (Two Micron All Sky Survey) and our QUIRC data, we identified the NIR counterpart for 278 (∼72%) X-ray sources (NIR-identified [NIR-IDed] X-ray
sources). Most of these sources are YSOs that belong to OMC-2 and OMC-3 considering
their magnitude and luminosity function in the K band. The rests of the X-ray sources areunidentified with NIR sources (NIR-unidentified [NIR-unIDed] X-ray sources).
For NIR-IDed X-ray sources, we estimated their mass and evolutional class using theirJ -, H -, K -band flux. We also derived their X-ray flux variability through the X-ray temporal
analysis, and their plasma temperature and X-ray luminosity by the X-ray spectral analysis.
By comparing the averaged X-ray properties among different mass ranges, we found thatYSOs in the intermediate (2.0 M¯ ≤ M < 10.0 M¯ ), low (0.2 M¯ ≤ M < 2.0 M¯ ), andvery low (M < 0.2 M¯ ) mass ranges have the same X-ray emission properties in contrast
to the high mass (M ≥ 10.0 M¯ ) sources. We further revealed that the X-ray emissions
from intermediate to very low mass YSOs consist of two thin-thermal plasma components
of different temperatures (kB T ∼ 1 keV and 2–3 keV). Based on the time-sliced X-ray
spectroscopy of some bright variable sources and on comparison with the sun and othermain and pre-main-sequence sources, we proposed that the soft X-ray component is fromcoronae while the hard component is due to flares.

3
Most of the NIR-unIDed X-ray sources are background extragalactic sources from their
hard X-ray spectra. However, the spatial distribution of these sources has an excess along
the ridge of star-forming cloud cores, which indicates that some of the NIR-unIDed Xray sources are related to star formations. We made follow-up imaging observations using
the University of Hawaii 88 inch (2.2 m) telescope, the Subaru telescope, and the Infrared
Telescope Facility in the J, H, K, L0 (3.8 µm), and H2 v = 1 − 0 S(1) (2.12 µm) bands inaddition to the centimeter interferometer imaging observation with Very Large Array (VLA).
Four NIR-unIDed X-ray sources are associated with jet and outflow systems and share many
multi-wavelength characteristics in common. We proposed that these X-ray emissions can be
explained by the high temperature plasma induced by protostellar jets. Other NIR-unIDed
X-ray sources along the cloud core do not have such association. However, their heavily
absorbed X-ray spectra and the association of some with sub-millimeter cores infer thatthey are heavily embedded X-ray-emitting YSOs, such as class 0 objects.

4Contents

1 Introduction

19

2 X-ray Observations on YSOs

25

2.1

2.2

Basic Features of YSOs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

26

2.1.1

Evolution and Classification . . . . . . . . . . . . . . . . . . . . . . .

26

2.1.2

Jets and Outflows . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

29

2.1.3

Magnetic Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . .

31

X-ray Observations on YSOs . . . . . . . . . . . . . . . . . . . . . . . . . . .

33

2.2.1

Low-mass YSOs: (1) Recent Results with Chandra . . . . . . . . . .

33

2.2.2

Low-mass YSOs: (2) X-ray Emission Mechanisms . . . . . . . . . . .

37

2.2.3

Very Low Mass YSOs (=Young Brown Dwarfs) . . . . . . . . . . . .

41

2.2.4

Intermediate-mass YSOs . . . . . . . . . . . . . . . . . . . . . . . . .

42

2.2.5

High-mass YSOs . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

42

2.2.6

Diffuse X-ray Emissions . . . . . . . . . . . . . . . . . . . . . . . . .

43

2.2.7

Problems to be Addressed . . . . . . . . . . . . . . . . . . . . . . . .

45

3 Orion Molecular Cloud 2 and 3
3.1

47

Global Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5

48

6

CONTENTS
3.2

3.3

3.4

3.5

Radio Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

49

3.2.1

Identifying Protostellar Cores with Dust Emissions . . . . . . . . . .

49

3.2.2

Centimeter Observations of Free-free Emissions . . . . . . . . . . . .

51

3.2.3

Millimeter Observations of Molecular Cores and Outflows . . . . . . .

56

3.2.4

Polarization Measurements . . . . . . . . . . . . . . . . . . . . . . . .

56

NIR Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

56

3.3.1

Bright Discrete Sources in OMC-2 . . . . . . . . . . . . . . . . . . . .

56

3.3.2

Surveys with Broad-band Imaging Observations . . . . . . . . . . . .

57

3.3.3

Narrow-band Studies of Molecular Outflows . . . . . . . . . . . . . .

58

Optical Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

59

3.4.1

Membership Studies with Proper Motion Measurements . . . . . . . .

59

3.4.2

Detection of Circumstellar Disks . . . . . . . . . . . . . . . . . . . . .

59

X-ray Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

62

3.5.1

Surveys in the Soft X-ray Band . . . . . . . . . . . . . . . . . . . . .

62

3.5.2

Surveys in the Hard X-ray Band . . . . . . . . . . . . . . . . . . . . .

62

4 Observing Facilities and Instruments
4.1

4.2

4.3

67

Chandra X-ray Observatory . . . . . . . . . . . . . . . . . . . . . . . . . . .

68

4.1.1

Spacecraft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

68

4.1.2

Optics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

69

4.1.3

Instrument (ACIS) . . . . . . . . . . . . . . . . . . . . . . . . . . . .

73

University of Hawaii 88 inch (2.2 m) Telescope . . . . . . . . . . . . . . . . .

79

4.2.1

Telescope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

79

4.2.2

Instrument (QUIRC) . . . . . . . . . . . . . . . . . . . . . . . . . . .

82

Subaru Telescope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

83

CONTENTS

4.4

4.5

7

4.3.1

Telescope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

83

4.3.2

Instrument (IRCS) . . . . . . . . . . . . . . . . . . . . . . . . . . . .

83

Infrared Telescope Facility . . . . . . . . . . . . . . . . . . . . . . . . . . . .

85

4.4.1

Telescope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

85

4.4.2

Instrument (NSFCam) . . . . . . . . . . . . . . . . . . . . . . . . . .

85

Very Large Array . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

87

4.5.1

Telescope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

87

4.5.2

Radio Interferometry . . . . . . . . . . . . . . . . . . . . . . . . . . .

89

5 Chandra and QUIRC Observations
5.1

5.2

93

X-ray Observation with Chandra/ACIS . . . . . . . . . . . . . . . . . . . . .

94

5.1.1

Observation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

94

5.1.2

Data Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

94

5.1.3

Source Extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

96

5.1.4

2MASS Counterpart of Chandra Sources . . . . . . . . . . . . . . . .

96

5.1.5

Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

NIR Observation with UH88/QUIRC . . . . . . . . . . . . . . . . . . . . . . 104
5.2.1

Observation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

5.2.2

Data Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

5.2.3

Source Extraction and Photometry . . . . . . . . . . . . . . . . . . . 107

5.2.4

2MASS Counterpart of QUIRC Sources . . . . . . . . . . . . . . . . . 109

5.2.5

Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

5.2.6

QUIRC Counterpart of Chandra Sources . . . . . . . . . . . . . . . . 114

6 NIR-IDed X-ray Sources: (1) NIR Properties

117

8

CONTENTS
6.1

6.2

NIR Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
6.1.1

K -band Luminosity Function . . . . . . . . . . . . . . . . . . . . . . 118

6.1.2

Color-color Diagram of QUIRC Sources . . . . . . . . . . . . . . . . . 119

6.1.3

Color-magnitude Diagram of QUIRC Sources . . . . . . . . . . . . . 120

The NIR-IDed X-ray Sources. . . . . . . . . . . . . . . . . . . . . . . . . . 124

6.2.1

Cloud Membership . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

6.2.2

Evolutional Class Estimates . . . . . . . . . . . . . . . . . . . . . . . 124

6.2.3

Mass and Bolometric Luminosity Estimates . . . . . . . . . . . . . . 127

7 NIR-IDed X-ray Sources: (2) X-ray Properties

131

7.1

Temporal Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

7.2

Spectral Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

7.3

7.2.1

Spectrum Models and Fittings . . . . . . . . . . . . . . . . . . . . . . 139

7.2.2

One-temperature Plasma Fittings . . . . . . . . . . . . . . . . . . . . 140

7.2.3

Two-temperature Plasma Fittings . . . . . . . . . . . . . . . . . . . . 151

7.2.4

Time-sliced Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . 159

Relations between Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . 162
7.3.1

X-ray absorption versus NIR extinction . . . . . . . . . . . . . . . . . 162

7.3.2

X-ray counts versus X-ray flux . . . . . . . . . . . . . . . . . . . . . . 162

7.3.3

X-ray counts versus X-ray luminosity . . . . . . . . . . . . . . . . . . 162

8 NIR-unIDed X-ray Sources
8.1

167

The Nature of NIR-unIDed X-ray Sources . . . . . . . . . . . . . . . . . . . 168
8.1.1

Background AGNs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

8.1.2

Sources with YSO-like Features . . . . . . . . . . . . . . . . . . . . . 175

CONTENTS
8.2

8.3

8.4

H2 Imaging Observations on OMC-3 . . . . . . . . . . . . . . . . . . . . . . 177
8.2.1

Observation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177

8.2.2

Analysis & Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178

NIR Observations on MMS 2 and MMS 3 . . . . . . . . . . . . . . . . . . . . 178
8.3.1

Observation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178

8.3.2

Analysis & Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181

8.3.3

Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187

Centimeter Observations on MMS 2 and MMS 3 . . . . . . . . . . . . . . . . 188
8.4.1

Observation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188

8.4.2

Analysis & Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189

8.4.3

Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190

9 Discussion
9.1

9.2

9.3

9

193

X-ray Emissions from NIR-IDed Sources: (1) Mass . . . . . . . . . . . . . . 194
9.1.1

X-ray Properties among Mass Ranges . . . . . . . . . . . . . . . . . . 194

9.1.2

High Mass Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194

9.1.3

Intermediate Mass to Very Low Mass Sources . . . . . . . . . . . . . 196

X-ray Emissions from NIR-IDed Sources: (2) Plasma Temperature . . . . . . 201
9.2.1

Two-temperature Plasma Emissions . . . . . . . . . . . . . . . . . . . 201

9.2.2

Origins of Two-temperature Plasma . . . . . . . . . . . . . . . . . . . 203

9.2.3

X-ray Properties among Evolutional Classes . . . . . . . . . . . . . . 206

X-ray Emissions from NIR-unIDed Sources . . . . . . . . . . . . . . . . . . . 208
9.3.1

Jet-induced Plasma Emissions . . . . . . . . . . . . . . . . . . . . . . 208

9.3.2

Magnetic Activities of Deeply Embedded YSOs . . . . . . . . . . . . 213

10

CONTENTS

10 Conclusions

217

A Chandra Sources and NIR Counterpart

235

B QUIRC Sources and 2MASS Counterpart

247

List of Figures
1.1

Orion Nebula . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

19

1.2

Absorption or scattering cross section by ISM . . . . . . . . . . . . . . . . .

20

2.1

Classification of YSOs and their SEDs . . . . . . . . . . . . . . . . . . . . .

28

2.2

Chandra image of ONC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

34

2.3

X-ray detections from class I protostars in R Coronae Australis . . . . . . .

35

2.4

X-ray detections from class I protostars in ρ Oph . . . . . . . . . . . . . . .

35

2.5

Magnetic field geometries of YSOs . . . . . . . . . . . . . . . . . . . . . . . .

38

2.6

Quasi-periodic flares from a protostar . . . . . . . . . . . . . . . . . . . . . .

38

2.7

DEM distribution of SU Aur . . . . . . . . . . . . . . . . . . . . . . . . . . .

40

2.8

X-ray CCD and grating spectra of TW Hya . . . . . . . . . . . . . . . . . .

40

2.9

X-ray detection from a HH object . . . . . . . . . . . . . . . . . . . . . . . .

44

3.1

Location of OMC-2 and OMC-3 (1) . . . . . . . . . . . . . . . . . . . . . . .

48

3.2

Location of OMC-2 and OMC-3 (2) . . . . . . . . . . . . . . . . . . . . . . .

50

3.3

1.3 mm map of OMC-2 and OMC-3 . . . . . . . . . . . . . . . . . . . . . . .

52

3.4

350 µm map of OMC-2 and OMC-3 . . . . . . . . . . . . . . . . . . . . . . .

53

3.5

Past NIR observations of OMC-2 and OMC-3 . . . . . . . . . . . . . . . . .

60

3.6

Past optical observations of OMC-2 and OMC-3 . . . . . . . . . . . . . . . .

61

11

12

LIST OF FIGURES
3.7

Past X-ray observations of OMC-2 and OMC-3 . . . . . . . . . . . . . . . .

64

4.1

Chandra spacecraft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

68

4.2

Configuration of HRMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

69

4.3

Energy dependence of HRMA effective area . . . . . . . . . . . . . . . . . .

70

4.4

Spatial dependence of HRMA effective area

. . . . . . . . . . . . . . . . . .

71

4.5

PSF of HRMA at on-axis . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

71

4.6

PSF of HRMA at off-axis. . . . . . . . . . . . . . . . . . . . . . . . . . . .

72

4.7

Configuration of ACIS array . . . . . . . . . . . . . . . . . . . . . . . . . . .

73

4.8

Energy resolution of ACIS . . . . . . . . . . . . . . . . . . . . . . . . . . . .

74

4.9

Effective energy range of ACIS . . . . . . . . . . . . . . . . . . . . . . . . . .

76

4.10 Energy dependence of the ACIS background . . . . . . . . . . . . . . . . . .

77

4.11 Long-term variation of the ACIS background . . . . . . . . . . . . . . . . . .

78

4.12 Spatial dependence of the ACIS background . . . . . . . . . . . . . . . . . .

80

4.13 Schematic view of the University of Hawaii 88 inch (2.2 m) telescope. . . .

81

4.14 QUIRC filter transmissions . . . . . . . . . . . . . . . . . . . . . . . . . . . .

83

4.15 Schematic view of Subaru telescope . . . . . . . . . . . . . . . . . . . . . . .

84

4.16 Broad-band filter transmissions of Mauna Kea system . . . . . . . . . . . . .

86

4.17 Configuration of VLA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

88

4.18 Schematic view of radio interferometry . . . . . . . . . . . . . . . . . . . . .

91

5.1

FOV of Chandra observation . . . . . . . . . . . . . . . . . . . . . . . . . . .

95

5.2

Pseudo-color image of Chandra observation . . . . . . . . . . . . . . . . . . .

97

5.3

2MASS Second Incremental Data Release coverage . . . . . . . . . . . . . .

98

5.4

Astrometric accuracy of 2MASS sources . . . . . . . . . . . . . . . . . . . .

99

LIST OF FIGURES

13

5.5

Photometric accuracy of 2MASS sources . . . . . . . . . . . . . . . . . . . . 100

5.6

Astrometric accuracy of Chandra sources . . . . . . . . . . . . . . . . . . . . 102

5.7

Histogram of Chandra source counts . . . . . . . . . . . . . . . . . . . . . . 103

5.8

FOV of QUIRC mosaic mapping observations . . . . . . . . . . . . . . . . . 105

5.9

Pseudo-color image of QUIRC observation . . . . . . . . . . . . . . . . . . . 108

5.10 Astrometric accuracy of QUIRC sources . . . . . . . . . . . . . . . . . . . . 110
5.11 Photometric accuracy of QUIRC sources . . . . . . . . . . . . . . . . . . . . 111
5.12 Completeness limit of QUIRC observations . . . . . . . . . . . . . . . . . . . 112
5.13 QUIRC K -band source counts . . . . . . . . . . . . . . . . . . . . . . . . . . 113
5.14 X-ray off-axis angle versus separation of the closest QUIRC–Chandra pairs . 114
5.15 NIR identification of ACIS-I sources . . . . . . . . . . . . . . . . . . . . . . . 115
6.1

Differential KLF of QUIRC sources . . . . . . . . . . . . . . . . . . . . . . . 119

6.2

Color-color diagram of QUIRC sources . . . . . . . . . . . . . . . . . . . . . 121

6.3

Color-magnitude diagram of QUIRC sources . . . . . . . . . . . . . . . . . . 122

6.4

Histogram of K -band extinction . . . . . . . . . . . . . . . . . . . . . . . . . 123

6.5

Color-color diagram of X-ray sources . . . . . . . . . . . . . . . . . . . . . . 126

6.6

Spatial distribution of Chandra sources (1) . . . . . . . . . . . . . . . . . . . 128

6.7

Color-magnitude diagram of Chandra sources . . . . . . . . . . . . . . . . . 129

6.8

Spatial distribution of Chandra sources (2) . . . . . . . . . . . . . . . . . . . 130

7.1

NIR-IDed Chandra sources for temporal analysis . . . . . . . . . . . . . . . . 133

7.2

Light curves of bright variable NIR-IDed Chandra sources (1) . . . . . . . . 134

7.3

Light curves of bright variable NIR-IDed Chandra sources (2) . . . . . . . . 135

7.4

Light curves of bright variable NIR-IDed Chandra sources (3) . . . . . . . . 136

14

LIST OF FIGURES
7.5

Light curves of bright variable NIR-IDed Chandra sources (4) . . . . . . . . 137

7.6

Light curves of bright variable NIR-IDed Chandra sources (5) . . . . . . . . 138

7.7

NIR-IDed Chandra sources for spectral analysis . . . . . . . . . . . . . . . . 141

7.8

One-temperature plasma fittings of bright NIR-IDed Chandra sources (1) . . 145

7.9

One-temperature plasma fittings of bright NIR-IDed Chandra sources (2) . . 146

7.10 One-temperature plasma fittings of bright NIR-IDed Chandra sources (3) . . 147
7.11 One-temperature plasma fittings of bright NIR-IDed Chandra sources (4) . . 148
7.12 One-temperature plasma fittings of bright NIR-IDed Chandra sources (5) . . 149
7.13 One-temperature plasma fittings of bright NIR-IDed Chandra sources (6) . . 150
7.14 Best-fit models of bright NIR-IDed ACIS-I sources . . . . . . . . . . . . . . . 151
7.15 Two-temperature plasma fittings of bright NIR-IDed Chandra sources (1) . . 154
7.16 Two-temperature plasma fittings of bright NIR-IDed Chandra sources (2) . . 155
7.17 Two-temperature plasma fittings of bright NIR-IDed Chandra sources (3) . . 156
7.18 Two-temperature plasma fittings of bright NIR-IDed Chandra sources (4) . . 158
7.19 Time-sliced spectroscopy of bright NIR-IDed Chandra sources (1) . . . . . . 159
7.20 Time-sliced spectroscopy of bright NIR-IDed Chandra sources (2) . . . . . . 160
7.21 X-ray absorption versus NIR extinction . . . . . . . . . . . . . . . . . . . . . 163
7.22 X-ray counts versus flux . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
7.23 X-ray counts versus luminosity . . . . . . . . . . . . . . . . . . . . . . . . . . 165
8.1

Chandra sources for spectral analysis . . . . . . . . . . . . . . . . . . . . . . 169

8.2

Power-law fittings of bright NIR-unIDed Chandra sources (1) . . . . . . . . . 171

8.3

Power-law fittings of bright NIR-unIDed Chandra sources (2) . . . . . . . . . 172

8.4

Histogram of Chandra hardness ratio . . . . . . . . . . . . . . . . . . . . . . 173

8.5

Power-law fittings of combined spectra of NIR-unIDed Chandra sources . . . 174

LIST OF FIGURES

15

8.6

Spatial distribution of NIR-unIDed Chandra sources . . . . . . . . . . . . . . 176

8.7

FOV of QUIRC H2 observations . . . . . . . . . . . . . . . . . . . . . . . . . 177

8.8

QUIRC H2 -band images of OMC-3 . . . . . . . . . . . . . . . . . . . . . . . 179

8.9

Chandra image of MMS 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

8.10 Schematic view of NIR dithering observations . . . . . . . . . . . . . . . . . 181
8.11 IRCS K -band image of MMS 2 . . . . . . . . . . . . . . . . . . . . . . . . . 182
8.12 NSFCam L0 -band image of MMS 2 . . . . . . . . . . . . . . . . . . . . . . . 183
8.13 IRCS H2 -band image of MMS 2 . . . . . . . . . . . . . . . . . . . . . . . . . 186
8.14 Color-color diagram of IRCS sources . . . . . . . . . . . . . . . . . . . . . . 187
8.15 VLA image of MMS 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189
8.16 Centimeter flux density versus outflow momentum rate . . . . . . . . . . . . 191
9.1

Light curve and spectrum of high mass sources . . . . . . . . . . . . . . . . . 197

9.2

Mass versus the ratio of X-ray and bolometric luminosity of NIR-IDed X-ray sources199

9.3

Mass versus X-ray luminosity of NIR-IDed X-ray sources . . . . . . . . . . . 200

9.4

Histogram of plasma temperature . . . . . . . . . . . . . . . . . . . . . . . . 202

9.5

DEM distributions of coronally active main sequence stars . . . . . . . . . . 204

9.6

Evolution of two-temperature plasma emissions . . . . . . . . . . . . . . . . 205

9.7

X-ray and NIR images of NIR-unIDed X-ray sources

9.8

Multi-wavelength view on MMS 2 . . . . . . . . . . . . . . . . . . . . . . . . 211

9.9

Schematic view of the X-ray and centimeter emissions of protostellar jet origin.211. . . . . . . . . . . . . 209

9.10 One-temperature plasma fittings of NIR-unIDed X-ray sources . . . . . . . . 213
10.1 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219

16

LIST OF FIGURESList of Tables
2.1

Multi-wavelength properties of low-mass YSOs . . . . . . . . . . . . . . . . .

29

2.2

Chandra and XMM-Newton studies of star-forming regions . . . . . . . . . .

36

2.3

Detected numbers of X-ray sources in Chandra survey studies . . . . . . . .

36

3.1

Properties of protostellar cores in OMC-2 and OMC-3 (1) . . . . . . . . . . .

54

3.2

Properties of protostellar cores in OMC-2 and OMC-3 (2) . . . . . . . . . . .

55

3.3

Past observations of OMC-2 and OMC-3 . . . . . . . . . . . . . . . . . . . .

65

3.4

Past NIR survey studies of OMC-2 and OMC-3 . . . . . . . . . . . . . . . .

66

3.5

Past X-ray survey studies of OMC-2 and OMC-3 . . . . . . . . . . . . . . .

66

4.1

Background count rate of Chandra ACIS . . . . . . . . . . . . . . . . . . . .

79

4.2

Comparison of NIR imagers used in this thesis . . . . . . . . . . . . . . . . .

82

4.3

VLA configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

88

4.4

VLA frequency bands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

89

5.1

QUIRC observation log . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

7.1

One-temperature plasma fittings of bright NIR-IDed Chandra sources . . . . 142

7.2

Two-temperature plasma fittings of bright NIR-IDed Chandra sources (1) . . 152

7.3

Two-temperature plasma fittings of bright NIR-IDed Chandra sources (2) . . 157
17

18

LIST OF TABLES
7.4

Two-temperature plasma fittings of bright NIR-IDed Chandra sources (3) . . 157

7.5

Time-sliced spectroscopy of bright NIR-IDed Chandra sources (1) . . . . . . 161

8.1

Power-law fittings of NIR-unIDed Chandra sources . . . . . . . . . . . . . . 170

8.2

Power-law fittings of combined spectra of NIR-unIDed Chandra sources . . . 173

8.3

IRCS & NSFCam sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

8.4

VLA sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190

9.1

Number of sources among mass ranges . . . . . . . . . . . . . . . . . . . . . 195

9.2

Comparison of X-ray properties among mass ranges . . . . . . . . . . . . . . 195

9.3

One-temperature plasma fittings of the high mass source . . . . . . . . . . . 196

9.4

Number of sources among classes . . . . . . . . . . . . . . . . . . . . . . . . 206

9.5

Comparison of X-ray properties among classes . . . . . . . . . . . . . . . . . 207

9.6

NIR-unIDed X-ray sources associated with jet and outflow systems . . . . . 210

9.7

One-temperature plasma fittings of NIR-unIDed Chandra sources . . . . . . 214

A.1 Chandra source list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236
B.1 QUIRC source list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248

Chapter 1
Introduction
The night sky, without stars, should be boring.
The stars we see are the mixture of young andold, which indicates that our universe keeps formingstars and not all stars were born at the beginning.
The sites of star formation, however, had been longinaccessible to human beings. They are born deep
in dense molecular clouds, so the visual light fromthese baby stars is almost extinct before reaching
our eyes. These star-forming clouds appear dark invisual images, hence are called dark clouds.
One of the representatives is the Orion molecular cloud (Fig. 1.1). Between two spectacular nebulae, there exists a dark lane. It appears to containnothing at a glance, but this is where stars are born.
Babies are surrounded by dense blankets of molecular clouds.
The veil was lifted at the advent of new astronomy in the 20th century, when we became able
to see the universe at any electromagnetic wavelengths. Figure 1.2 shows the absorption or scattering cross section of electromagnetic waves by the19

Figure 1.1: Visual image (600 ×940 ) of theOrion nebula (M42), the brightest nebulaseen from the Earth (Guinness World Records
2003[58] ). Our study field (the dashed square)
is located ∼200 north of the nebula. Courtesy;
the Kiso Observatory, the University of Tokyo.

20

CHAPTER 1. INTRODUCTION

interstellar medium (ISM). Typically, cloud cores have the visual extinction of AV > 10 mag.
In other words, the visual light (λ ≈ 550 nm) from forming stars is attenuated to less than
10−4 times. However, when we observe at the wavelengths of lower cross sections like X-ray,infrared, and radio lights, we can delve into the dense clouds.

Figure 1.2: Absorption or scattering cross section by ISM of the electromagnetic wave at a given wavelength
in the infrared (IR), optical, ultraviolet (UV), extreme ultraviolet (EUV), and X-ray band (Ryter 1996[168] ).
The Chandra and XMM-Newton satellites cover the range of 0.1–10.0 keV. The wavelengths of lower crosssection have larger penetrating power into dense matter.

In 1967, Becklin & Neugebauer[19] discovered an infrared star in the Orion nebula. Thisobject, unlike seven other objects found in their study field, had no optical counterpart.
Successive near-infrared (NIR) observations found a dozen of sources with similar characteristics in dark clouds, and revealed that they are the stars at their birth. This was the firstobservational evidence of forming stars.
These stars are yet to begin the nuclear fusion at their center, hence are called pre-mainsequence sources or young stellar objects (YSOs). They are cool (T = 100–1000 K at thesurface) and embedded sources that are just generated from gravitationally contracting cold
(T ∼ 10 K) gas. It was astonishing, therefore, that strong X-ray emissions corresponding to
the temperature of T ∼ 10 MK were found from these sources. Babies were found to be crying
loud! In 1980’s, the Einstein Observatory detected soft (E < 2 keV) X-ray emissions from T21
Tauri stars (TTSs), which comprise a class of YSOs with the mass of 0.5–2.0 M¯ 1 and the ageof ∼1 Myr (Feigelson, & DeCampli 1981[50] ; Montmerle et al. 1983[133] ). Using the Advanced
Satellite for Cosmology and Astrophysics (ASCA) satellite, Koyama et al. (1996)[107] further
discovered hard (E > 2 keV) X-ray emissions from a cluster of class I protostars, which are
low-mass YSOs younger than TTSs (∼0.1 Myr). Protostars are severely extinct by dense
cores and are hard to access even with NIR observations.

The X-ray studies on YSOs are important in a wide area of astronomy and astrophysics.
First, the X-ray emissions from these stars are so intense that they can affect heavily on thecircumstellar environment. Glassgold, Feigelson, & Montmerle (1999)[70] discussed that thephotoionization of circumstellar matter by X-rays can surpass the collision ionization bycosmic rays inside the distance from the core ofÃLXr ≈ 0.02 ×
29
10 ergs s−1

!

[pc],

(1.1)

where LX is the X-ray luminosity of YSOs. At active phases of YSOs, LX can exceed 1030 –
1031 ergs s−1 , which indicates that the X-ray ionization is the dominant mechanism inside thewhole cloud core of typically ∼0.1 pc. As circumstellar matter should be ionized before being
coupled with the magnetic field, the ionization rate and efficiency are key parameters in starformations. Without establishing the average features and revealing the mechanism of X-ray
emissions from YSOs, therefore, we would not be able to understand the star formation
process, a long-standing subject in astronomy and astrophysics.
Once the ubiquity of the X-ray emission is established for protostars as well as for TTSs,
X-ray observations will be one of the most efficient tools to conduct a census on star-forming
clouds. With a larger penetrating power than NIR observations (particularly of hard X-rays;
Fig. 1.2), with a better spatial resolution than FIR–millimeter observations, and with a very
wide field of view, we will soon encounter a large number of “X-ray-selected” YSOs. The
investigation on these sources, we believe, will proceed our understanding on star births.
X-ray observations on protostars and TTSs with the mass of ∼1 M¯ also give us apicture on the past activities of our sun. Its enhanced activity by 3–5 orders of magnitudein the past should have given a large impact on the evolution of the solar system.
Finally, YSOs are one of the enigmatic sources in the universe that emit radiation byreleasing their gravitational energy, such as neutron stars, galactic black holes, and active
1

Masses in the unit of solar mass (2.0 × 1033 g) are given with M¯ .

22

CHAPTER 1. INTRODUCTION

galactic nuclei (AGNs). These sources have many processes in common; formation of jets,gravitational energy release through accretion disks, and acceleration of charged particles.
YSOs are much closer to us than the other types of sources, which enables us to investigate
fine structures of these high energy phenomena.

Previous studies with the Einstein, ROSAT, and ASCA satellites on the X-ray emissions
from YSOs are mainly focused on low-mass sources. Higher mass YSOs have lower population
densities and evolve more quickly, making these samples fewer and more distant. Lower mass
YSOs are also difficult to observe because of their intrinsic faintness. The X-ray spectra of
low-mass YSOs revealed that the X-ray emissions are of thin-thermal plasma origin. In
addition, their X-ray light curves often show flares with a rapid rise and a slow decay, which
are similar in profile but higher in flux and temperature compared to solar flares. These
lead to the general consensus that the X-ray emissions from low-mass YSOs are solar-like;
YSOs have thin-thermal plasma to emit X-rays with occasional flares triggered by magnetic
reconnections. However, not all observational results are accountable by a simple extensionof the solar flares. Moreover, YSOs of different mass ranges (M < 0.2 M¯ or M > 2.0 M¯ )are not well studied. What are different between YSOs and our sun? Do higher-mass orlower-mass YSOs possess high temperature plasma like low-mass YSOs? If so, how is theplasma generated? Are there any other X-ray emission mechanisms besides flares? The aimof this thesis is to give an answer to these questions through a multi-wavelength study onOrion molecular cloud 2 and 3 (OMC-2 and OMC-3).
Our study field is located at the center of the dark lane in Figure 1.1 and contains YSOs
at all evolutional phases from class 0 protostars to TTSs in a wide range of mass from earlytype stars to brown dwarfs. OMC-2 and OMC-3 are full of phenomena related to star formation; radio jets, molecular outflows, Herbig-Haro (HH) objects, sources with accretion disks,dust emissions, etc. In particular, the condensation of protostars in OMC-2 and OMC-3 isthe highest among all near-by star forming regions (Reipurth, Rodrı́guez, & Chini 1999[162] ).
They are proximate to us at a distance of ∼450 pc (Genzel & Stutzki 1989[66] ) and have anappropriate size of 100 ×200 that can be covered with one field of view of the current X-ray
cameras. All these features make these clouds ideal sites for our study.
In order to study the X-ray emissions from YSOs, we employ a multi-wavelength approach. OMC-2 and OMC-3, although hard to see in the optical light, can be accessed with
X-ray, NIR, and radio observations (see our X-ray and NIR images of the field in Figs. 5.2

23
and 5.9). Information obtained at different wavelengths complements with each other. In
addition to the X-ray observations that trace high temperature (T =1–100 MK) plasma of
YSOs, NIR–millimeter observations detect blackbody emissions from stars, accretion disks
and dusts, which indicate the mass and evolutional phase. Outflows and jets from YSOs canbe seen through the optical, NIR, millimeter, and centimeter observations. In this thesis, we
conduct a deep X-ray and NIR observations on OMC-2 and OMC-3 respectively using the
Chandra X-ray Observatory and the University of Hawaii 88 inch (2.2 m) telescope. Followup observations are also performed on interesting sources using the Subaru telescope, theInfrared Telescope Facility (IRTF), and the University of Hawaii 88 inch (2.2 m) telescopeat the NIR band and the Very Large Array (VLA) at the centimeter band.
The plan of this thesis is as follows. We review on the recent progress of X-ray observations on YSOs in Chap. 2 and previous multi-wavelength observations of our study field
in Chap. 3. The basic features of the telescopes and instruments used in this work are summarized in Chap. 4. In Chap. 5, we explain our X-ray and NIR observations on OMC-2 andOMC-3. In total, 385 X-ray sources are found in our observation. By correlating them withour 1448 NIR sources as well as NIR all-sky survey catalog sources, we discriminate the NIRidentified (NIR-IDed) and NIR-unidentified (NIR-unIDed) X-ray sources. The following two
chapters (Chap. 6 and Chap. 7) are devoted for the NIR and X-ray properties of the NIRIDed X-ray sources, where we estimate the mass and the evolutional phase of our samples
and discuss the X-ray spectral and temporal features of these sources. In Chap. 8, we deal
with the NIR-unIDed X-ray sources, where we focus on sources related to star formation. In
Chap. 9, we discuss the X-ray emission mechanisms of both the NIR-IDed and NIR-unIDedsources. Finally, we conclude in Chap. 10. Figure 10.1 will help readers to follow the flow of
this thesis.

24

CHAPTER 1. INTRODUCTION

Chapter 2
X-ray Observations on YSOs
Contents
2.1

2.2

Basic Features of YSOs . . . . . . . . . . . . . . . . . . . . . . . .

26

2.1.1

Evolution and Classification . . . . . . . . . . . . . . . . . . . . . .

26

2.1.2

Jets and Outflows . . . . . . . . . . . . . . . . . . . . . . . . . . .

29

2.1.3

Magnetic Activities . . . . . . . . . . . . . . . . . . . . . . . . . . .

31

X-ray Observations on YSOs . . . . . . . . . . . . . . . . . . . .

33

2.2.1

Low-mass YSOs: (1) Recent Results with Chandra . . . . . . . . .

33

2.2.2

Low-mass YSOs: (2) X-ray Emission Mechanisms . . . . . . . . . .

37

2.2.3

Very Low Mass YSOs (=Young Brown Dwarfs) . . . . . . . . . . .

41

2.2.4

Intermediate-mass YSOs . . . . . . . . . . . . . . . . . . . . . . . .

42

2.2.5

High-mass YSOs . . . . . . . . . . . . . . . . . . . . . . . . . . . .

42

2.2.6

Diffuse X-ray Emissions . . . . . . . . . . . . . . . . . . . . . . . .

43

2.2.7

Problems to be Addressed . . . . . . . . . . . . . . . . . . . . . . .

45

25

26

CHAPTER 2. X-RAY OBSERVATIONS ON YSOSIn the first section (Sect. 2.1) of this chapter, we briefly review the basic feature of
YSOs. In the following section (Sect. 2.2), we review the X-ray observations on YSOs.
As the progress made on low-mass YSOs with the Einstein, ROSAT, and ASCA satellites
are concisely summarized in a review paper by Feigelson & Montmerle (1999)[53] , we focus
mainly on recent advances made with the following Chandra and XMM-Newton observations.
The problems to be solved on the X-ray emissions from YSOs are summarized in the last
subsection, for which this thesis tries to give an answer.

2.1

Basic Features of YSOs

2.1.1

Evolution and Classification

A star formation begins with the onset of gravitational collapse of molecular cloud cores withthe density of 10−17 –10−16 g cm−3 . Gas and dust keep contracting freely on the central core
until the density reaches ∼10−13 g cm−3 . At this density, the core becomes optically thick.
The thermal pressure adiabatically increases and finally balances with the gravitational force
to stop dynamical accretion. YSOs at this stage are called protostars. Protostars commonly
accompany jets and outflows, which function to release angular momentum. Without themechanism of angular momentum release, they can not keep accumulating mass because
matters inside the Keplerian radius can not accrete onto their surface.
After most of the circumstellar matter accretes onto the star or is blown away by jets andoutflows, YSOs quasi-statically contract with increasing temperature and density. YSOs atthis stage are called T Tauri stars (TTSs). The contraction continues with a constant surface
temperature, which makes TTSs move down along the Hayashi track on the HertzsprungRussell (H-R) diagram (Hayashi 1966[81] ). The circumstellar disk gradually disappears as
TTSs evolve. TTSs are divided into two classes; classical TTSs (cTTSs) that are in theearlier phase of TTSs with an optically thick accretion disk and weak-lined TTSs (wTTSs)
that are in the later phase with an optically thin or no accretion disk. Finally, when nuclear
burning starts at the center, YSOs turn into the main sequence stars. In general, “pre-mainsequence source” indicates TTSs, while “YSO” indicates the collection of protostars and
TTSs.
The evolution of low-mass YSOs, which have been the main targets of previous obser-

2.1. BASIC FEATURES OF YSOS

27

vations due to their proximity and ample samples, is traced by several measurements. One
is to use the equivalent width (EW ) of the Hα emission in the optical band, which is a directindicator of mass accretion. CTTSs are defined as YSOs with EW > 10 Å while wTTSs
are with EW < 10 Å. As cTTSs are younger (∼106 yr in case of low-mass YSOs) thanwTTSs (∼107 yr) and have mass accretion from their circumstellar disk, they show larger
EW values than wTTSs.
YSOs in much younger phases than TTSs are invisible with the optical light. Lada &Wilking (1984)[112] , Adams et al. (1987)[1] , and Lada (1991)[113] established a classification
scheme using the NIR to mid-infrared (MIR) excess, in which younger YSOs show stronger
NIR excess emission in addition to their photospheric blackbody emission. This excess
emission comes from circumstellar disks and envelopes that have lower temperature (T =100–1000 K) than the photosphere (T ∼ 3000 K). The spectral index between 2.2 µm (theK band) and 10 µm (the M band) in the spectral energy distributions (SEDs) of YSOs;¯

d log νFν ¯¯α=−¯d log ν ¯ 2.2−10 µm(2.1)

is used to classify sources into class I, class II, and class III (Fig. 2.1). As class I sources
are younger (∼105 yr), they show larger NIR excess hence larger α values than class II andclass III sources. When the M -band flux is not available, which is often the case becauseof the difficulty of sensitive observations in this band, the J (1.2 µm)-, H (1.6 µm)-, andK -band fluxes are alternatively used to discriminate among classes using the color-color
diagram (Sect. 6.1). CTTSs usually have the class II SED, while wTTSs have the class III
SED. In this thesis, we use cTTSs and wTTSs for the same meaning as class II and class III
sources.
In addition to the class I, II, and III objects, André, Ward-Thompson, & Barsony(1993)[5] introduced class 0 objects, which are younger than class I. The lower temperatureand higher obscuration make this class sources invisible even with NIR and MIR lights.
Barsony (1994)[17] defined the class 0 sources with the following features: (1) undetectable
at the wavelengths of λ < 10 µm, (2) a high ratio of Lsmm /Lbol , where Lsmm and Lbol are thesub-millimeter and bolometric luminosity, (3) a relatively narrow SED resembling that of asingle blackbody at T ≤ 30 K, (4) presence of a molecular outflow, (5) existence of centimeter
continuum emission, and (6) presence of HH objects. Class 0 objects are considered to beat the age of 104 –105 yr, which are the youngest stellar objects that are accessible with thecurrent observational technology.

28

CHAPTER 2. X-RAY OBSERVATIONS ON YSOS

Figure 2.1: Classification of YSOs and their SEDs (Bachiller 1996[13] )2.1. BASIC FEATURES OF YSOS

29

Table 2.1: Multi-wavelength properties of low-mass YSOs

properties
age (yr)accretion disk
X-ray emission
jet and outflow
non-thermal radio

2.1.2

YSOs
class 0class I
class II
infalling
evolved classicalprotostar protostar T Tauri
104
105
106
thick
thick
thick
?
yes
?

strongyes
yesstrongyesno (?)

main
sequenceclass III
weak-lined
T Tauri
107>107
thin orplanetarynonexistent system (?)
strong
weak
no
no
yes
yes

Jets and Outflows

Jets and outflows from YSOs are traced using several observational tools. From the origin,radio jets at the distance of ∼100 AU, optical jets and fast neutral winds at the distance of∼0.01 pc, and molecular outflows at the distance of 0.1–1 pc are ubiquitously observed fromprotostars. More evolved YSOs accompany weak or no jet and outflow phenomena.

Radio Jets
Radio jets from YSOs were first studied by Cohen, Bieging, & Schwartz (1982)[37] . They
appear to be thermal emissions at the centimeter band and are detected from almost all
the class 0 and some of the class I protostars. The observational characteristics of theseemissions in near-by star-forming regions are summarized as (1) the elongated morphology at
sub-arcsecond scale, (2) association with both high and low luminosity objects, (3) alignment
within a few degrees with the large scale outflow, (4) weak flux with the flux density typicallyin the range of 0.5–10 mJy, (5) positive or flat spectral indices, and (6) dynamical time scalesof only a few years (Anglada 1996[8] ).
Because these emissions are associated with low as well as high luminosity YSOs, thefree-free emission from the HII region produced by stellar photo-ionization is unlikely. The
alignment with and the elongation in the direction of global outflows strongly infer that theseemissions are related to jet and outflow phenomena. Curiel, Cantó, & Rodrı́guez (1987)[42]30

CHAPTER 2. X-RAY OBSERVATIONS ON YSOS

and Curiel et al. (1989)[43] proposed an idea of shock-induced ionization, where protostellar
jets collide into high density ambient matter at the speed of a few times of 100 km s−1 , andthe UV photons are irradiated from the shock front to produce HII regions. An empirical
relation is seen between the outflow momentum rate and the centimeter flux, which supports
this scenario (Anglada 1992[7] ). Martı́, Rodrı́guez, & Reipurth (1998)[122] monitored one of
the radio jets from YSOs and found that a pair of centimeter condensations are travelingaway from the central core at the speed of ∼500 km s−1 .

Optical Jets
Because Herbig (1951)[82] and Haro (1952)[78] were the first to identify knotty structures in theOrion region, they are called HH objects. Together with optical jets that were detected laterby Mundt & Fried (1983)[138] and Mundt et al. (1984)[139] , these are the typical phenomenathat characterize star-forming regions. These emissions are considered to originate fromcooling regions of high velocity shocks that are produced as a result of highly collimated jetsfrom YSOs colliding into dense ambient matter.
HH objects and optical jets altogether have the following characteristics: (1) knotty
structures sometimes spaced periodically, (2) bow-shock-shaped HH objects located at theend of a series of knots, (3) half of the HH objects and optical jets with a bipolar structure,(4) collimated structure of the opening angles in the range of 5◦ –20◦ , and (5) the typicallength, velocity and number density of optical jets in the range of 0.01–1 pc, 200–600 km s−1 ,and 10–200 cm−3 (Edwards, Ray, & Mundt 1993[46] ).

Fast Neutral Winds
CTTSs are known to posses high velocity (100–300 km s−1 ) wind based on the P Cygni-type
profile in various lines in the optical wavelengths (Kuhi 1964[110] ; Hartmann 1982[80] ). Similar
high velocity winds were also detected from much younger phase of YSOs (protostars) using
the neutral HI line (Giovanardi et al. 1992[69] ). Although cTTSs and protostars are in different phases of the YSO evolution, the stellar wind from these sources is considered to havethe same origin because they have similar velocities, mechanical energies, and momentum
flux. The origin of the phenomena is not well known, but it is somewhat related to accretion
disks. A detailed discussion on this topic can be found in Edwards et al. (1993)[46] .

2.1. BASIC FEATURES OF YSOS

31

Molecular Outflows
Circumstellar matter is dragged by high velocity and high density jet from protostars, whichforms molecular outflows moving at the velocity of 10–200 km s−1 . They are well traced
by rotational transition lines of molecules in the millimeter band and vibrational-rotationaltransition lines in the NIR band. Snell, Loren, & Plambeck (1980)[174] was the first to detect
a bipolar CO outflow from L1551 region. More than 200 outflows are cataloged to date.
The vibrational-rotational transition lines of H2 and the rotational transition lines of CO
are commonly used. The H2 and CO outflows together with the optical jets are powerful tracers of jet and outflow activities from protostars that work complementarily, where the lowest
velocity (∼10 km s−1 ) component is traced by CO, the moderate velocity (∼100 km s−1 )component by H2 , and the highest velocity (∼500 km s−1 ) component in the optical wavelengths.
About a half of molecular outflows are observed to have a bipolar structure with apair of red-shifted and blue-shifted robes and the powering source is always at the center ofthe symmetry. They are moderately collimated with the opening angle of 10◦ –50◦ . Recent
progress of observations on molecular outflows can be found in Fukui et al. (1993)[59] ,Eislöffel et al. (2000)[47] , and Richer et al. (2000)[163] .

2.1.3

Magnetic Activities

As YSOs are fully convective in their interior and rotate much faster (∼1 day) than main
sequence stars (∼30 days in case of the sun), they are expected to possess enhanced magnetic
activities. This is supported by three major observational indications: (1) X-ray flares that
trace the magnetic reconnections, (2) centimeter gyro-synchrotron emissions that indicate
accelerated charged particles to the energy of ∼1 MeV, and (3) various optical photometricand spectroscopic studies. X-ray emissions are separately reviewed in Sect. 2.2.

Gyro-synchrotron Emissions
In addition to the thermal free-free emissions, YSOs emit non-thermal emissions in thecentimeter band. These emissions are considered to originate from the gyro-synchrotron
emissions for the following reasons (André 1996[6] ). First, they show flux variability of the32

CHAPTER 2. X-RAY OBSERVATIONS ON YSOS

time scale of hours to days, including intense “radio flares” (Feigelson & Montmerle 1985[51] ;Becker & White 1985[18] ; Bieging & Cohen 1989[23] ). Second, they have a moderate degreeof circular polarization of |V /I| <5% at outbursts and |V /I| <20% at quiescence. Third, abrightness temperature of >107 K is measured by Very Long Baseline Interferometer (VLBI)
observations, directly confirming the size of the emitting regions. Electrons with the energyof ∼1 MeV are gyrating around large-scale magnetic fields with the size of ∼5 stellar radii
and the strength of 1–10 G, which emit non-thermal emissions detectable at the centimeter
band.
These emissions are only seen in evolved YSOs except for a class I protostar (Feigelson,
Carkner, & Wilking 1998[52] ). The centimeter flux of this emission is somewhat related to the
X-ray luminosity, which can be extended to magnetically-active main sequence stars such as
RS CVns and dMe stars. A recent simultaneous observation on an RS CVn-type binary in
the X-ray and the centimeter band using XMM-Newton and VLA reported the detection of
the Neupert effect, in which the time derivative of the X-ray light curve is proportional to the
centimeter light curve (Güdel et al. 2002[75] ). This confirms to understand the phenomena insolar analog; i.e., accelerated electrons via magnetic reconnections reach the chromosphereto heat the plasma that emits X-rays.

Optical Studies

The most successful approach to measure the magnetic field strength of TTSs is the Zeeman splitting measurements, although this is applicable only to ideal cases. Some TTS
samples were studied and revealed to have a strong magnetic field with the strength of 0.5–
4 kG (Johnstone & Penston 1986[97] ; Johnstone & Penston 1987[98] ; Johns-Krull, Valenti &Koresko 1999[95] ).
There are many indirect methods to investigate magnetic activities. Doppler imaging
technique showed that large cool spots are moving on the surface of some TTSs. Hα andMgII emission lines, which are the tracers of chromospheric activities, are other indicators ofstrong magnetic activities of these sources.

2.2. X-RAY OBSERVATIONS ON YSOS

2.2

X-ray Observations on YSOs

2.2.1

Low-mass YSOs: (1) Recent Results with Chandra

33

In X-ray observations as well as observations in other wavelengths, low mass (0.2–2.0 M¯ )YSOs have been the main targets. Previous studies using Einstein, ROSAT, and ASCA
are concisely summarized in a review paper by Feigelson & Montmerle (1999)[53] . Here, we
briefly review recent results made with Chandra (Table 2.2).
Two capabilities are required for the X-ray studies on YSOs: (1) the spatial resolutionof ∼100 to resolve each YSO member in a usually crowded star-forming region and (2) the
sensitivity in the hard X-ray band (E > 2 keV) to penetrate through dark clouds. The
preceding X-ray observatories did not meet either of these two requirements; ASCA theformer and Einstein and ROSAT the latter. Chandra has both capabilities, which makes
this satellite the best tool for YSO studies. The charge coupled device (CCD) detector
onboard Chandra further enables us to obtain temporal (∆t ∼ 3 s) and spectral (∆E ∼100 eV) information on a photon basis. With a wide field of view (FOV) of 170 ×170 , we cansimultaneously derive the light curve and spectrum of ∼100 X-ray sources in a star-forming
region (Fig. 2.3). Table 2.3 summarizes the survey studies made with Chandra.
The X-ray properties of TTSs were found to have the following characteristics: (1) thinthermal plasma spectrum with the X-ray luminosity of LX < 1030 –1031 ergs s−1 and theplasma temperature of kB T = 0.5–5 keV, (2) flare-like flux variability with some hints ofspectral hardening, (3) an empirical relation of LX /Lbol = 10−3 –10−5 , and (4) no clear difference in X-ray properties between cTTSs and wTTSs. All these results are already obtainedwith previous Einstein, ROSAT, and ASCA observations (Feigelson & Montmerle 1999[53] ).
Chandra studies on TTSs confirmed these results with larger number of samples.
Major advances are seen in the studies of class I protostars. In the era of ASCA andROSAT, only a limited number of class I samples were identified (Fig. 2.3, Koyama et al. 1996[107] ;Kamata et al. 1997[103] ; Ozawa et al. 1999[145] ; Tsuboi et al. 2000[187] using ASCA and
Grosso et al. 1997[72] ; Neuhäuser & Preibisch 1997[141] ; Grosso 2001[73] using ROSAT ). With
poor photon statistics, it was difficult to address their X-ray properties. A textbook caseof the X-ray studies on class I protostars was presented by Imanishi, Koyama, & Tsuboi(2001a)[91] using the Chandra deep exposure observation on the ρ Ophiuchi dark cloud(Fig. 2.4). They detected X-rays from ∼70% of class I protostars and their candidates.

34

CHAPTER 2. X-RAY OBSERVATIONS ON YSOS

Figure 2.2: Chandra/ACIS image of ONC (Feigelson et al. 2002b[55] ). Inside a 170 ×170 region of ACIS-I,∼1000 X-ray sources were detected.

Moreover, they investigated their X-ray spectra and light curves and found that class I
protostars have similar X-ray features with TTSs, with higher plasma temperature, larger
column density and X-ray luminosity, and more occasional flare-like events.
The X-ray sources in star-forming regions that are not identified with NIR and opticalsources can be an interesting topic. The number of these sources is 30–100 in some (Table 2.3). Although this number depends on the significance level of the source detection
algorithm and the completeness limit of the NIR and optical catalog, it generally exceeds
the expected number of background sources, particularly in cases of Orion Nebula Cluster(ONC; Feigelson et al. 2002b[55] ) and OMC-2/3 (Tsujimoto et al. 2002a[189] ; 2003[192] [thisthesis]) observations. The nature of these X-ray sources is not studied at all yet. However,considering the high sensitivity of Chandra observations that are comparable or deeper than
optical and NIR observations, some of these optically and NIR unidentified sources can bea new class of YSOs.

2.2. X-RAY OBSERVATIONS ON YSOS

35

Figure 2.3: Hard X-ray detections from class I protostars in R Coronae Australis with ASCA (http://wwwcr.scphys.kyoto-u.ac.jp/IAU/gallery/gallery.html). Unlike soft X-rays (left), hard X-rays (right) can penetrate into the densest part of the cloud core, detecting hard X-ray emissions for the first time from class I
protostars (Koyama et al. 1996[107] ).

Figure 2.4: X-ray detections and their light curves from class I protostars in the ρ Ophiuchi cloud with
Chandra. Courtesy; Kensuke Imanishi (Kyoto University).

165

310

318

450

450

ρ Oph

IC 348

NGC 1333

ONC

OMC-2/3

89

83

38

53

101

exposure
(ks)
18
13
8
N/A
13

87 (1×10−7 )
215 (3×10−6 )
127 (1×10−6 )1075 (1×10−5 )
385 (1×10−5 )
12

30

N/A

2

7

number of sources
all sources (SLa) class Ib
BDc

107 (K < 16)

101 (V < 20)

32 (I < 23)

39 (K < 19)

28 (K < 15)

no IDd(CLe)Tsujimoto et al. (2002a[189] ; 2003[192] ) [this thesis]

Getman et al. (2002)[67]Feigelson et al. (2002a)[54]

Imanishi et al. (2001a)[91] ; 2001b[92]Preibisch & Zinnecker (2001)[155]references

e The band and the limiting magnitude of the optical and NIR catalogs that were used to correlate with X-ray sources.

d The number of X-ray sources not identified with optical and NIR sources.

c The number of X-ray-emitting brown dwarfs, which includes brown dwarf candidates identified with NIR photometry observations alone.

b The number of X-ray-emitting class I protostars.

a The significance level in the X-ray source detection algorithm. The wavdetect program was used in all studies.

distance(pc)

regionTable 2.3: Detected numbers of X-ray sources in Chandra survey studies

a Studies by XMM-Newton. Other studies were made with Chandra.

diffuse emissions
Arches Cluster (Yusef-Zadeh et al. 2002[198] ), M 8 (Rauw et al. 2002[159] )aHH-2 (Pravdo et al. 2001[153] ), L1551 IRS5 (Favata et al. 2002[49] )aNGC 3603 (Moffat et al. 2002[132] ), RCW 38 (Wolk et al. 2002[195] )HH objects . . . . .

TTSs (grating) .

W 3 (Hofner et al. 2002[90] ), IRAS 19410+2336 (Beuther et al. 2002[22] ), M 8 (Rauw et al. 2002[159] )a
TW Hya (Kastner et al. 2002[104] )OMC-2/3 (Tsuboi et al. 2001[188] ; Tsujimoto et al. 2002a[189] )Mon R2 (Kohno et al. 2002[106] ; Preibisch et al. 2002b[157] ), Sgr B2 (Takagi et al. 2002[178] )NGC 1333 (Getman et al. 2002[67] )ONC (Garmire et al. 2000[62] ; Schulz et al. 2001[169] , Feigelson et al. 2002a[54] ; 2002b[55] ; 2003[56] )regions (references)ρ Oph (Imanishi et al. 2001a[91] ; 2001b[92] ; 2002[93] )IC 348 (Preibisch & Zinnecker 2001[155] ; 2002a[156] )high-mass YSOs

intermediate- &survey studies . .

categories

Table 2.2: Chandra and XMM-Newton studies of star-forming regions

36
CHAPTER 2. X-RAY OBSERVATIONS ON YSOS

2.2. X-RAY OBSERVATIONS ON YSOS

2.2.2

37

Low-mass YSOs: (2) X-ray Emission Mechanisms

The X-ray emission mechanism of YSOs should account for many observational results obtained so far: (1) the soft X-ray emissions (E < 2 keV) as well as hard X-ray emissions(E > 2 keV), (2) flare-like variability as well as quiescent emissions, and (3) some empirical
relations, such as LX /Lbol ∼ 10−3 –10−5 . The proposed scenarios do not successfully accountfor all of these pieces of evidence.
The most favored idea is the magnetic reconnection model, in which rapid energy releaseby reconnections of magnetic field lines (flares) generates and maintains the high temperatureplasma. This model well explains the flare-like flux variability with rapid rise and slow decay
and hard X-ray spectra exceeding 2 keV.
Four geometries of magnetic field lines are considered (Feigelson & Montmerle 1999[53] ;Fig. 2.5): (1) both feet on the stellar surface, (2) connecting the star and the circumstellar
disk, (3) above the corotation radius, and (4) both feet on the circumstellar disk. The geometry (1), which is the same with the sun, is most plausible. The reconnections are caused
as a result of differential rotation and convection of the star. In contrast, Montmerle et al.
(2000)[134] proposed a magnetic field geometry bridging between the star and the disk (geometry 2). This is based on the ASCA result by Tsuboi et al. (2000)[187] , who detectedquasi-periodic flares from a class I protostar in the ρ Ophiuchi cloud (YLW 15; Fig. 2.6).
They assumed the radiative cooling for the flux decay in these flares, and derived that themagnetic loop length is ∼14 times of the stellar radius. Favata, Micela, Reale (2001)[48]
noted that the loop length is overestimated unless we take the recurrent heating during
flares into account. At present, no clear difference is seen between cTTSs and wTTSs in
X-ray luminosity functions, which casts some doubt on the geometry where the disk plays a
key role (geometry 2 and 4).
Whatever the geometry is, the magnetic reconnection model does not account for thesteady X-ray emissions at the quiescent phase. In the case of our sun, attempts have not beensuccessful to explain the steady emissions (the solar coronae) by the integration of small flares(Shimizu 1995[170] ; Aschwanden et al. 2000[9] ; Aschwanden & Charbonneau 2002[10] ). Shimizu(1995)[170] discussed, using the Yohkoh Soft X-ray Telescope data, that the occurrence rateof flares is expressed with a single power-law function of the flare energy (E) asdN∝ E −α .
(2.2)
dE
He derived α = 1.5–1.6 in the energy range down to ∼1027 ergs. The α value of less than

38

CHAPTER 2. X-RAY OBSERVATIONS ON YSOS

Figure 2.5: Magnetic field geometries of YSOs (Feigelson & Montmerle 1999[53] ).

Figure 2.6: Quasi-periodic flare from a protostar in the ρ Ophiuchi cloud detected with ASCA
(Tsuboi et al. 2000 [187] ). The time evolution of the X-ray luminosity, plasma temperature, and emission
measure are given in the upper, middle, and lower panels, respectively.

2.2. X-RAY OBSERVATIONS ON YSOS

39

2 indicates that smaller flares are not the dominant source of the total energy released byflares of all scales, if we assume that the power-law can be extrapolated to lower energies. In
fact, the integration of all observed flares account for at most only one fifth of the heating
rate required for the active-region coronae. With this in mind, we have to deal with flaresand coronae as different phenomena, although the heating mechanism of coronae is still quite
puzzling.
Another difficulty that the magnetic activity scenario is confronted with is that we
see no clear relation between the X-ray luminosity and the rotation period (e.g.; Feigelson et al. 2003[56] ). This is in sharp contrast with magnetically active main sequence stars,
where we see a strong anti-correlation between the soft X-ray luminosity and rotation period(Pallavicini et al. 1981[147] ). This should be a natural deduction when the magnetic activity
is the origin of the X-ray emissions.
Skinner & Walter (1998)[173] presented an interesting result using the ASCA observationon the brightest cTTSs in the Taurus-Auriga complex (SU Aur). They argued that there
exist two different X-ray emissions by constructing the differential emission measure (DEM)
distribution of this source. The bimodal plasma temperature distribution is quite similar to
those seen in active late-type main sequence stars with X-ray emissions of coronal origin. If
the X-ray emissions from YSOs are commonly the combination of some different mechanisms,
all previous discussions correlating LX or kB T with stellar parameters should be re-examined.
Kastner et al. (2002)[104] proposed yet another scenario based on their high-resolution
grating spectroscopy observation on a cTTS (TW Hya) using Chandra (Fig. 2.8). They
argued that the X-ray emission arises from the hot spot or spots on the stellar surface locatedat the root of accretion funnels. Three lines of evidence support this idea: (1) The DEM
distribution is sharply peaked at T ∼ 3 MK, which is in sharp contrast with broad DEMs
seen in coronally active late-type stars. (2) The temperature of T ∼ 3 MK is consistent
with the value expected from the adiabatic shock caused by gas accretion at the speed of
150–300 km s−1 , which is measured from the broadening of Hα line emissions. (3) The
high-resolution spectroscopy enabled them to measure the plasma density using the densitysensitive triplet lines of OVII and NeIX . In combination with the emission measure, theemitting volume was derived to be only 10−6 of the stellar volume, which is smaller thantypical coronal X-ray sources. We have no other grating spectroscopy results on YSOs besides
this source. Further studies with a larger number of samples are quite prospective.
Zhekov, Palla, & Myasnikov (1994)[201] presented a model calculation to account for the

40

CHAPTER 2. X-RAY OBSERVATIONS ON YSOS

Figure 2.7: Differential emission measure distributions of SU Aur (a pre-main-sequence source; solid ) andEK Dra (a main sequence star; dashed ) derived from ASCA observations (Skinner & Walter 1998[173] ).

Figure 2.8: X-ray spectra of TW Hya taken with ASCA/SIS (a CCD spectrometer; upper pannel ) andChandra/HETG (a grating spectrometer; lower panel ). The density sensitive triplet lines of OVII and NeIX
are clearly resolved at ∼22 Å and ∼11 Å in the grating spectrum, which serve as a powerful tool to determine
the electron density of the plasma (Kastner et al. 2002[104] ).

2.2. X-RAY OBSERVATIONS ON YSOS

41

soft X-ray emission with colliding winds from YSO binaries at the speed of 300–500 km s−1
and the mass loss rate of 10−8 –10−6 M¯ yr−1 . This model, although it well explains thesoft X-ray temperature and the X-ray luminosity, has difficulties in understanding the hard
X-ray emissions and flaring temporal behaviors of YSO X-rays.

2.2.3

Very Low Mass YSOs (=Young Brown Dwarfs)

Recent X-ray observations are also capable to study brown dwarfs in star-forming regions.
Brown dwarfs are tiny objects with mass less than 0.08 M¯ that never possess nuclear
burning during their life. A series of studies using ROSAT were the first to report thedetection of X-ray emissions from young brown dwarfs (Neuhäuser & Comerón 1998[142] ;Neuhäuser et al. 1999[143] ) in the Chamaeleon, Taurus, and ρ Ophiuchi regions. The numberof X-ray-emitting brown dwarfs drastically increased with the following Chandra studies on
the Orion Nebula Cluster (Garmire et al. 2000[62] ; Feigelson et al. 2002a[54] ), ρ Ophiuchi(Imanishi et al. 2001b[92] ), and IC 348 (Preibisch & Zinnecker 2001[155] ; 2002a[156] ). At
present, X-ray observations in near-by star forming regions have reached the brown dwarf
limit.
When observed with a deep exposure, X-ray observations on brown dwarfs are no longer
a mere detection experiment. Imanishi et al. (2001b)[92] studied the X-ray properties of four
X-ray-brightest brown dwarfs and their candidates in the ρ Ophiuchi cloud with a ∼100 ks
exposure with Chandra. They found that brown dwarfs have similar X-ray properties withlow-mass YSOs with: (1) the temperature of ∼1–2.5 keV, (2) flux variability from somesources, and (3) LX /Lbol = 10−3 –10−5 . Based on this similarity in X-ray properties, they
discussed that young brown dwarfs have the same X-ray emission mechanism with low mass
YSOs.
Interestingly enough, X-ray emissions are detected from only a few field brown dwarfs(Fleming, Giampapa, & Schmitt 2000[57] ; Rutledge et al. 2000[167] ) in spite of their muchcloser distance to us. It appears that brown dwarfs decrease their X-ray activity as they
evolve. This behavior is commonly seen in low mass stars, which are X-ray active in the
pre-main-sequence stage and become inactive as they evolve into the main sequence stage.
However, as brown dwarfs have no clear definitions of pre-main-sequence and main sequencewith no nuclear fusion in their life, it is not quite clear why their X-ray activity changes inthe same manner as low mass stars.

42

2.2.4

CHAPTER 2. X-RAY OBSERVATIONS ON YSOSIntermediate-mass YSOs

Intermediate-mass YSOs in the mass range of 2.0–10.0 M¯ are still not clear to have
any X-ray emissions. Zinnecker & Preibisch (1994)[202] studied 21 Herbig Ae/Be sources(intermediate-mass counterpart of TTSs) with ROSAT and found that 11 of them emit Xrays. Hamaguchi (2000)[77] obtained a similar X-ray detection rate with the ASCA data.
He also discussed, based on the hard X-ray spectra and flare-like variability of some Herbig
Ae/Be stars, that these sources also have magnetic activity similar to low-mass YSOs. Zinnecker & Preibisch (1994)[202] , on the contrary, raised a possibility that the X-ray emissions
from these sources can be from their low-mass companion and not intrinsically from theintermediate-mass YSOs. Feigelson et al. (2002a)[54] studied the ONC sources with A or B
spectral types and discussed that the X-ray emissions can be fully attributable to their lowmass companions. Their samples, however, are not confined to pre-main-sequence sources
and may include main sequence intermediate-mass sources. This can mislead the conclusion
because intermediate-mass main sequence sources do not emit X-rays at all due to their lackof convection zones.

2.2.5

High-mass YSOs

Some Chandra observations detected X-ray emissions from ultra-compact HII regions inmassive star-forming regions at a few kpc away. The ultra-compact HII regions are dueto the UV photoionization from the central young massive objects of >10 M¯ and aretraced using the free-free emissions in the centimeter wavelengths. The X-ray emissions
were reported from the infrared source “n” in the BN/KL region in OMC-1 at 450 pc(Garmire et al. 2000[62] ), IRS 1, IRS 2, IRS 3, and as in the Monoceros R2 cloud at 830 pc(Kohno et al. 2002[106] ; Preibisch et al. 2002b[157] ), and IRS 2, IRS 2a, and IRS 3a in theW 3 complex at 2.3 kpc (Hofner et al. 2002[90] ).
The most notable characteristics of these X-ray emissions are their hard spectra of kB T >2 keV and X-ray variability. These features are similar to those of low-mass YSOs, indicatingthat these X-ray emissions are also of magnetic origin. On the contrary, the LX /Lbol valuesof some high mass YSOs are in the range of 10−6 –10−8 (e.g., Kohno et al. 2002[106] ), which
are too small for an empirical value of 10−3 –10−5 for low-mass YSOs and are comparable tohigh-mass main sequence sources that emit X-rays of stellar wind origin. The X-ray emission
mechanism of these sources is not still clear.

2.2. X-RAY OBSERVATIONS ON YSOS

43

Whatever the X-ray emission mechanism of high-mass YSOs, their hard X-ray emissions
provide us with a unique tool to search for young massive stars in dense molecular clouds.
The penetrating power of hard X-rays is comparable to radio bands. Moreover, unlike
millimeter and centimeter emissions, we can trace the central star with their X-ray emissions.
Takagi et al. (2002)[178] illustrated this unique capability by detecting highly absorbed (NH= 1–4×1023 cm−2 ) hard (kB T = 5–10 keV) X-ray emissions from ultra-compact HII regionsin the Sagittarius B2 cloud at the distance of 8.5 kpc away.

2.2.6

Diffuse X-ray Emissions

High sensitivity observations using Chandra and XMM-Newton extended the X-ray studies
to weaker but new X-ray emissions. One example is HH objects. In strong adiabatic shocks,
the plasma temperature of T is expected at the shock velocity of vs (Raga, Noriega-Crespo,
Velázquez 2002[158] ), whereµ5

T = 1.5 × 10

vs100 km s−1

¶2

[K].

(2.3)

With the typical velocity of optical jets (200–300 km s−1 ), we can expect soft X-ray emissions
from HH objects.
Pravdo et al. (2001)[153] reported the detection of X-ray emission from HH-2 using
Chandra. The emission has a very soft spectrum with an extended spatial distribution. They
proposed that this emission originates from the plasma with the temperature of ∼106 K
and the plasma is generated by collision of the protostellar jet with ISM at the speed of∼250 km s−1 . A similar soft X-ray emission was later reported by Favata et al. (2002)[49]from L1551 IRS5 using XMM-Newton.
Another example of new findings is the diffuse X-ray emissions from massive star-forming
regions. Moffat et al. (2002)[132] reported the detection of the diffuse emission with theextent of ∼20 (4 pc) from the center of NGC 3603. The emission is of thermal origin withkB T ∼ 3.1 keV and the total luminosity of LX ∼ 2 × 1034 ergs s−1 . They probably arise frommerging or colliding hot stellar winds of massive stars. Similar diffuse thermal emissions
were also found by Yusef-Zadeh et al. (2002)[198] in the Arches Cluster and by Rauw et al.
(2002)[159] in the Lagoon Nebula (M8). Wolk et al. (2002)[195] reported, on the other hand,that the diffuse X-ray emission found from RCW 38 is of non-thermal origin. They insisted
that this emission might be attributable to synchrotron emissions from hidden supernova

44

CHAPTER 2. X-RAY OBSERVATIONS ON YSOS

Figure 2.9: Soft X-ray detection from a HH object (HH-2) with Chandra (Pravdo et al. 2001[153] ). The
upper panel gives the Hubble Space Telescope image with the position of the Chandra and VLA sources witha circle and squares, respectively. The lower panel gives the X-ray event map of Chandra with the contours
giving the Hα intensity.

2.2. X-RAY OBSERVATIONS ON YSOS

45

remnants. These diffuse X-ray emissions from star-forming regions are restricted to massive
star-forming regions at the distance of a few kpc, which makes it difficult to assess thecontamination by a complex of point sources. Further studies are necessary to establish the
diffuse X-ray emissions from star-forming regions.

2.2.7

Problems to be Addressed

Among a number of problems raised on X-ray emissions from YSOs, we try to give an answer
for the following issues in this thesis.
(1) Are there any class I protostars or brown dwarfs in our field? The X-ray emitting
samples of these sources are still limited, so it is important to enrich them for further
investigations. The combination of our sensitive X-ray and NIR observations is quite usefulfor this purpose.
(2) Do intermediate-mass YSOs intrinsically emit X-rays? The possible contamination
by low-mass binary companions or main sequence intermediate-mass sources prevented previous studies from drawing a definite conclusion. We confine the sample to ostensively single,
pre-main-sequence intermediate-mass sources, and compare the binary rate and the X-ray
detection rate of these well-defined intermediate-mass YSO samples to address whether they
are intrinsic X-ray emitters.
(3) Are there any differences in averaged X-ray features among sources in different mass
ranges? Using large number of samples, we can first compare the averaged features of YSOs
spanning from intermediate-mass to brown dwarfs in a single star-forming region.
(4) What are the X-ray emission mechanisms of all these samples? Skinner & Walter (1998)[173] raised a possibility that the X-ray emission mechanism of YSOs can be the
combination of different mechanisms that is represented by a bimodal structure in plasma
temperatures. Their result alone is not conclusive, because their source (SU Aur) is a spectroscopic binary (Bouvier et al. 1986[25] ) that can mimic two-temperature plasma. Twothings are required. First, we need to try multi-temperature plasma models for the X-ray
spectral fittings. All previous Chandra papers present only the result of one-temperature
fittings. Second, we need to deal with a large number of samples collectively to statistically
discuss whether the bimodal temperature structure is attributable to the binarity or not.
(5) What is the nature of X-ray sources that have no NIR counterpart? We conduct

46

CHAPTER 2. X-RAY OBSERVATIONS ON YSOS

multi-wavelength follow-up observations to reveal their nature.

Chapter 3
Orion Molecular Cloud 2 and 3
Contents
3.1

Global Properties . . . . . . . . . . . . . . . . . . . . . . . . . . .

48

3.2

Radio Observations . . . . . . . . . . . . . . . . . . . . . . . . . .

49

3.2.1

Identifying Protostellar Cores with Dust Emissions . . . . . . . . .

49

3.2.2

Centimeter Observations of Free-free Emissions . . . . . . . . . . .

51

3.2.3

Millimeter Observations of Molecular Cores and Outflows . . . . .

56

3.2.4

Polarization Measurements . . . . . . . . . . . . . . . . . . . . . .

56

NIR Observations . . . . . . . . . . . . . . . . . . . . . . . . . . .

56

3.3.1

Bright Discrete Sources in OMC-2 . . . . . . . . . . . . . . . . . .

56

3.3.2

Surveys with Broad-band Imaging Observations . . . . . . . . . . .

57

3.3.3

Narrow-band Studies of Molecular Outflows . . . . . . . . . . . . .

58

Optical Observations . . . . . . . . . . . . . . . . . . . . . . . . .

59

3.4.1

Membership Studies with Proper Motion Measurements . . . . . .

59

3.4.2

Detection of Circumstellar Disks . . . . . . . . . . . . . . . . . . .

59

X-ray Observations . . . . . . . . . . . . . . . . . . . . . . . . . .

62

3.5.1

Surveys in the Soft X-ray Band . . . . . . . . . . . . . . . . . . . .

62

3.5.2

Surveys in the Hard X-ray Band . . . . . . . . . . . . . . . . . . .

62

3.3

3.4

3.5

47

48

CHAPTER 3. ORION MOLECULAR CLOUD 2 AND 3

In this chapter, we review the past observations of OMC-2 and OMC-3. In Sect. 3.1, wesummarize the global properties of OMC-2 and OMC-3 and illustrate that these regions are
one of the best targets for our study. In the following sections, past observations (Table 3.3)
in the radio (Sect. 3.2), NIR (Sect. 3.3), optical (Sect. 3.4), and X-ray (Sect. 3.5) band
are reviewed. In particular, we stress how to utilize these results in this thesis and how tocomplement them with our new observations.

3.1

Global Properties

The Orion molecular cloud (OMC) is the cradle of star formation studies. Its proximity to
us and the brightness have been attracting many astronomers and astrophysicist who intend
to understand the formation of stars in a wide mass range. OMC is located 15–20◦ south
to the Galactic plane (Fig. 3.1) and is comprised of a large complex of molecular clouds(Fig. 3.2). Among them, the Orion A, Orion B, Northern Filament, and λ Ori clouds are
physically associated with each other, judging from the fact that they are located at similar
distances and have similar velocities. The association of these clouds with Monoceros R2and Southern Filament is not certain yet (Maddalena et al. 1986[120] ).

Figure 3.1: CO intensity map along the Galactic plane (Dame, Hartmann, & Thaddeus 2001[44] ). The
Orion A (Ori. A) molecular cloud, at the right side of the panel, is located at the Galactic longitude andlatitude of l ∼ 210◦ and b ∼ −20◦ .

OMC-1 is the most prominent and densest cloud core in the Orion A. It contains a youngstellar cluster called the Orion Nebula Cluster (ONC) that embraces an OB association
known as the Trapezium. The Trapezium is the powering source of the spectacular HII
region of the Orion (M42; Fig. 1.1). OMC-2 and OMC-3 are located ∼120 and ∼230 north to
ONC. OMC-2 was first discovered by chance as a complex of NIR and molecular emissions

3.2. RADIO OBSERVATIONS

49(Gatley et al. 1974[63] ). OMC-3 is another intensity peak of radio emissions at the north of
OMC-2.
Successive studies in OMC-2 revealed that it is a high density as well as high column
density core with the kinematic temperature (24 K) much lower than that of OMC-1 (70 K).
OMC-3 has even lower kinematic temperature of 19 K (Castets & Langer 1995[30] ). These
indicate that both OMC-2 and OMC-3 are the sites of on-going star formation. The starformation activity first occurred in OMC-1 and propagated into the north to OMC-2 andOMC-3, which are currently active star-forming clouds. To illustrate this, these clouds arefull of phenomena related to star formations; jets, molecular outflows, HH objects, accretion
disks, dust emissions, etc.
Throughout this thesis, we adopt the age of OMC-2 and OMC-3 to be ∼1 Myr, whichis estimated based either on the H-R diagram of some bright NIR sources in OMC-2 (Johnson et al. 1990[96] ), the K -band luminosity function of cluster members (Ali & DePoy 1995[2] ),direct spectroscopic evidence (Hodapp & Deane 1993[87] ; Hillenbrand 1997[85] ), the presenceof rich outflows and NIR excesses commonly seen in YSOs (Strom, Strom, & Merrill 1993[175] ;Chen & Tokunaga 1994[34] ; Jones et al. 1994[101] ), and the I - and V -band magnitudes of member sources (Rebull et al. 2000[160] ). The distance to OMC-2 and OMC-3 is assumed to be∼450 pc (Genzel & Stutzki 1989[66] ).

3.2

Radio Observations

3.2.1

Identifying Protostellar Cores with Dust Emissions

Radio continuum observations in OMC-2 and OMC-3 have been conducted at 1.3 mm(Mezger et al. 1990[129] ; Chini et al. 1997[35] ), 850 µm, 450 µm (Johnstone & Bally 1999[99] ),and 350 µm (Lis et al. 1998[117] ). All these observations aim to detect dust continuum emissions of protostellar cores and to determine the position and distribution of contracting cores,
which pilots the star formation studies in these regions.
Mezger, Zylka, & Wink (1990)[129] obtained a 1.3 mm map of OMC-1 and OMC-2
with the angular resolution of ∼9000 and ∼1100 , respectively. In OMC-2, they identified six
millimeter clumps (FIR 1–FIR 6). Chini et al. (1997)[35] took a higher-resolution image of
OMC-2 and OMC-3 at 1.3 mm and detected a chain of 21 cores (MMS 1–MMS 10 in OMC-3,

50

CHAPTER 3. ORION MOLECULAR CLOUD 2 AND 3

ORION BORION A

Figure 3.2: Schematic view of the Orion A, Orion B, and Monoceros R2 cloud complex (Maddalena et al. 1986[120] ), and major stars of the Orion. OMC-2 and OMC-3 belong to the Orion A, andare located at the position marked with the cross.

3.2. RADIO OBSERVATIONS

51

FIR 1a–FIR 6d in OMC-2; Table 3.1) using the Institut de Radio Astronomie Millimétrique(IRAM) telescope. Combining the James Clerk Maxwell Telescope (JCMT) photometry from350 µm to 2 mm and the Infrared Astronomical Satellite (IRAS ) photometry from 12 µm
to 100 µm, they showed that most cores have a high ratio of sub-millimeter to bolometricluminosity (Lsmm /Lbol ), insisting that these cores are class 0 protostar candidates. They
also derived the temperature and mass of each condensation (Tables 3.1 and 3.2). Figure 3.3
shows the 1.3 mm intensity map of OMC-2 and OMC-3. Throughout this thesis, we use thismap as the landmark of these regions.
Lis et al. (1998)[117] followed with a 350 µm imaging observation with a larger FOV
including OMC-2 and OMC-3. They detected 350 µm emissions from almost all the 1.3 mm
cores and 10 additional ones (Fig. 3.4).
Johnstone & Bally (1999)[99] observed this region in 450 µm and 850 µm and foundsimilar “integral-shaped” structure identified in 1.3 mm. They constructed the spectral
index map, which constrains the dust emissivity and temperature at each position.

3.2.2

Centimeter Observations of Free-free Emissions

Reipurth et al. (1999)[162] observed a 60 ×150 region in OMC-2 and OMC-3 with VLA. The
D configuration in 3.6 cm was used, which yields an angular resolution of ∼800 (Sect. 4.5).
In total, 14 sources were detected above ∼0.1 mJy, ten of which are associated with theprotostellar cores seen in the 1.3 mm continuum. Some 3.6 cm sources are also associatedwith H2 (Yu, Bally, & Devine 1997[199] ) and CO and HCO+ (Aso et al. 2000[11] ) outflows,
HH objects (Reipurth, Bally, & Devine 1997[161] ), H2 O masers (Morris & Knapp 1976[135] ;Genzel & Downes 1979[65] ), and sub-millimeter emissions (Lis et al. 1998[117] ). Due to theseassociations, these 3.6 cm emissions are considered to be free-free emissions from the HII
regions generated by shocks from protostar jets.
The detection of thermal free-free centimeter emissions gives strong evidence that there
is a class 0 or class I protostar at its origin, with active mass accretion. Seven and four
3.6 cm emissions were respectively found in OMC-2 and OMC-3. In one of the protostellar
cores in OMC-3, we found that D configuration observations are not fine enough to correlatewith our X-ray and NIR data, so we obtained the A configuration image in this region. The
details of analysis and result of this observation are discussed in Sect. 8.4.

52

CHAPTER 3. ORION MOLECULAR CLOUD 2 AND 3

Figure 3.3: Distribution of protostellar cores seen in 1.3 mm (Chini et al. 1997[35] ). OMC-2 and OMC-3
are separated by the dashed line into south and north. The equinox is in B1950.0.

3.2. RADIO OBSERVATIONS

53

Figure 3.4: Distribution of protostellar cores seen in 350 µm (Lis et al. 1998[117] ). The equinox is in
B1950.0.

54

CHAPTER 3. ORION MOLECULAR CLOUD 2 AND 3

Table 3.1: Properties of protostellar cores in OMC-2 and OMC-3 (1)objecta

MMS 1
MMS 2
MMS 3f
MMS 4
MMS 5
MMS 6
MMS 7
MMS 8
MMS 9
MMS 10

FIR 1cFIR 1bFIR 1a
FIR 2
FIR 3
FIR 4
FIR 5
FIR 6aFIR 6bFIR 6cFIR 6dR.A.
(J2000.0)
05:35:18
05:35:18
05:35:19
05:35:20
05:35:22
05:35:23
05:35:26
05:35:27
05:35:26
05:35:32

decl.
counterpartb
13(J2000.0) 350 µm H CO+c
H2 d
OMC−3
−05:00:20 CSO 5........ ......
−05:00:35 CSO 6 AC 3
flow B−05:00:51 CSO 7........ ......
−05:00:53 CSO 8........ ......
−05:01:14 CSO 9. . . . . . . . flow C−05:01:32 CSO 10 AC 4
flow A−05:03:53 CSO 12 AC 8
flow F−05:05:17 CSO 13 . . . . . . . . . . . . . .
−05:05:42 CSO 14 AC 10
flow H−05:05:42 . . . . . . . AC 12......

05:35:24
05:35:23
05:35:25
05:35:24
05:35:28
05:35:27
05:35:26
05:35:23
05:35:23
05:35:21
05:35:20

OMC−2−05:07:10 CSO 16−05:07:32 CSO 17−05:07:53 CSO 18−05:08:33 CSO 20−05:09:33 CSO 22−05:10:00 CSO 23−05:10:23 CSO 24−05:12:36 CSO 28−05:12:03 CSO 25−05:13:15 CSO 29−05:13:15 CSO 30........
AC 14........
AC 15........
AC 17........
........
........
........
........

3.6 cme.......
VLA 1.......
.......
.......
VLA 3
VLA 4.......
VLA 5.......

. . . . . . VLA 7...... .......
. . . . . . VLA 8
flow O . . . . . . .
flow J VLA 11. . . . . . VLA 12...... .......
. . . . . . VLA 14
flow L . . . . . . .
...... .......
...... .......

follow Chini et al. (1997)[35] for OMC-3 sources and Mezger, Zylka, &Wink (1990)[129] for OMC-2 sources.
b Lis et al. (1998)[117] .
a Nomenclaturesc Aso et al. (2000)[11] .
d Yu, Bally, & Devine (1997)[199] .
e Reipurth, Rodrı́gues, & Chini (1999)[162] .
f

The position of MMS 3 in Chini et al. (1997)[35] is incorrect. The corrected coordinate is given in
Tsuboi et al. (2001)[188] .

3.2. RADIO OBSERVATIONS

55

Table 3.2: Properties of protostellar cores in OMC-2 and OMC-3 (2)objecta

Lbol a Lbol /Lsmm a
(L¯ )

MMS 1
MMS 2
MMS 3
MMS 4
MMS 5
MMS 6
MMS 7
MMS 8
MMS 9
MMS 10

<55
.....
.....
<56
.....
<60
76
<89
<94
.....

FIR 1cFIR 1bFIR 1a
FIR 2

128
.....
<138
<157

<61
..........
..........
<72..........
<50
129
<178
<145
..........

Td a
Mgas a(K) (M¯ )
OMC−3
20–25
18
..... .....
..... .....
20–25
11..... .....
15–25
36
26
8
20
9
20
10
..... .....

356..........
..........
<320

OMC−2
33
5
..... .....
..... .....
20
8

Ṁ b
Ṗ b
(M¯ yr−1 ) (M¯ km s−1 yr−1 )..........
7.4×10−6
dittoedittoe6.7×10−6..........
1.4×10−5..........
3.6×10−5
3.3×10−5..................
3.0×10−5
dittoedittoe1.9×10−5..................
8.8×10−5..................
15.1×10−5
11.3×10−5

3.1×10−5
dittofdittof..........

9.8×10−5
dittofdittof..................

a Chini et al. (1997)[35] .
b Aso et al. (2000)[11] .
c Mass loss rate of the outflows.
d Momentum loss rate of the outflows.
e MMS 2, MMS 3, and MMS 4 were not resolved in the observations by Aso et al. (2000)[11] .
f

FIR 1a, FIR 1b, and FIR 1c were not resolved in the observations by Aso et al. (2000)[11] .

56

3.2.3

CHAPTER 3. ORION MOLECULAR CLOUD 2 AND 3

Millimeter Observations of Molecular Cores and Outflows

Mapping observations with various density tracers have been conducted on OMC-2 andOMC-3; with 13 CO by Bally et al. (1987)[14] , C18 O by Dutrey et al. (1993)[45] , 13 CO, C18 O,
C32 S, and C34 S by Castes & Langer (1995)[30] , and CI (3 P1 –3 P0 ) and CO (J = 3 − 2) by
Ikeda et al. (1999)[94] . These observations identified a filamentary structure extending from
OMC-1 to OMC-2 and OMC-3. Hundreds of dust condensations along this filament wereextracted by two high resolution mapping observations in CS (J = 1−0) by Tatematsu et al.
(1993)[179] and in NH3 by Cesaroni & Wilson (1994)[31] .
With the Nobeyama 45 m telescope, Aso et al. (2000)[11] observed OMC-2 and OMC-3
in H13 CO+ (J = 1 − 0), HCO+ (J = 1 − 0), and CO (J = 1 − 0) lines, detecting eightmolecular outflows in addition to 18 molecular cores. Blue and red lobes of these outflows
are well aligned with the outflows seen in the H2 observation (Yu et al. 1997[199] ). The
spatial resolution of their map (the beam width of ∼1500 ) is comparable to those taken in thecontinuum observations by Chini et al. (1997)[35] and Lis et al. (1998)[117] , which enabled
them to determine the origin, velocity, mass loss rate, and outflow momentum rate of theseoutflows. No interferometer millimeter observation has been conducted on these regions.

3.2.4

Polarization Measurements

Matthews & Wilson (2000)[124] and Matthews, Wilson, & Fiege (2001)[125] measured thepolarization of dust emissions in OMC-3 at 850 µm. They found that the polarization
vectors are highly aligned. The field direction in the plane of the sky (B⊥ ) was found to beperpendicular to the filamentary structure of OMC-3.

3.3

NIR Observations

3.3.1

Bright Discrete Sources in OMC-2

A series of NIR studies in OMC-2 and OMC-3 has been made concentrating on bright discrete
sources. Gatley et al. (1974)[63] was the first to observe OMC-2 with 10 broad-bands from
1.6 µm to 20 µm and found five separate components (IRS 1–IRS 5). Based on their lack of
the optical counterparts, their SEDs, and the association with CO emissions, they suggested

3.3. NIR OBSERVATIONS

57

that these NIR sources are protostars. The nature of these emissions was the main issue inthe following three papers published once in four years (Thronson & Thompson 1982[182] ;Pendleton et al. 1986[149] ; Johnson et al. 1990[96] ).
Thronson & Thompson (1982)[182] measured the K -band spectra of IRS 3 and IRS 4,
and revealed that IRS 4 shows many emission lines of molecular hydrogen. They pointed outthat the series of H2 v = 2 − 1 lines are relatively strong compared to v = 1 − 0 lines insteadof their low absolute flux, hence they are more likely produced by UV pumping. This was
the first candidate of UV-pumped H2 sources, although the shock pumping origin of theseH2 emission lines could not be ruled out.
Pendleton et al. (1986)[149] conducted NIR–FIR imaging and NIR polarimetry observations of OMC-2. They showed that IRS 1 and IRS 4 are reflection nebulae based on theirhigh degree of polarization. Their FIR map revealed compact sources at IRS 1 and IRS 4,
which are considered to be responsible for the reflection.
The final conclusion on the nature of these NIR sources was derived by Johnson et al.
(1990)[96] , who compiled the SEDs of 11 discrete sources including IRS 1–IRS 5. Most of these
SEDs are accountable with the combination of NIR emissions from reddened stellar photosphere and thermal emissions from circumstellar matter, indicating the pre-main-sequence
nature of these sources. By de-reddening these SEDs, they also estimated the temperature,
extinction, mass and age of these sources. The picture of OMC-2 was thus established to bea cluster of low-luminosity, low- to intermediate-mass YSOs with ages of ∼1 Myr embedded
in an extended dust cloud.

3.3.2

Surveys with Broad-band Imaging Observations

In 1990’s, the advent of large format NIR arrays prompted survey studies of star-forming
clouds. Jones et al. (1994)[101] measured the J -, H -, and K -band magnitude of 219 sourcesin a 150 ×50 region containing OMC-2. The 90% completeness limit of their survey was K ∼14 mag. They found that almost all the sources brighter than 13 mag are cloud members
and some sources show flux variability.
Ali & DePoy (1995)[2] conducted a similar survey study in a larger field (1472 arcmin2 )with a deeper exposure (K ∼ 14.5 mag at the 90% completeness) but in the K band alone.
They detected 3548 sources and constructed the surface density map of these sources, iden-

58

CHAPTER 3. ORION MOLECULAR CLOUD 2 AND 3

tifying two density peaks; i.e., the Trapezium and OMC-2. They also studied the K -band
luminosity function (KLF) of these peaks and found that KLF of the Trapezium is consistent
with a Miller & Scalo (1979)[131] initial mass function (IMF) with the age of ∼106 yr. No
age estimate of OMC-2 was available due to the paucity of sources (∼33).
Carpenter (2000)[26] and Carpenter, Hillenbrand, & Skrutskie (2001b)[28] extended thesurvey study of the Orion A cloud with 2MASS data, which provides the J -, H -, and K s -band
magnitude down to 16.0, 15.4, and 14.8 mag at the 93.8% completeness, respectively. They
showed that there is an enhanced stellar surface density over a 0.4◦ ×2.4◦ region containing
the Trapezium, OMC-2 and OMC-3.
One of the unique outcomes of 2MASS project was presented by Carpenter, Hillenbrand, & Skrutskie (2001b)[28] , who systematically studied the NIR variability properties ofpre-main-sequence sources in a 0.84◦ ×6◦ region across OMC. A total of 1235 variables areclassified into several patterns; periodic stars, eclipsing systems, stars steadily increase theirbrightness, stars that change colors redder or bluer, long-term variables, and so on. Models
such as hot or cool spots on the surface, changes in the mass accretion rate, inner disk radius,
or extinction are employed to account for their variability. This is the most comprehensive
study of NIR variability seen in pre-main-sequence sources.
We found that all above NIR surveys are not deep enough to match our X-ray observation of OMC-2 and OMC-3. Therefore, we conducted the deeper (K ∼ 16 mag) and morecomprehensive NIR observations in these regions (this thesis; Tsujimoto et al. 2003[192] ). The
details of analysis and result of this observations are discussed in Sect. 5.2.

3.3.3

Narrow-band Studies of Molecular Outflows

The vibrational-rotational transition of v = 1−0 S(1) works as an effective coolant of the excited hydrogen molecules, so this emission line is commonly used as a tracer of outflows fromprotostars (Bally et al. 1993[15] ; Hodapp & Ladd 1995[88] ). Yu et al. (1997)[199] conducteda narrow-band imaging observation in H2 v = 1 − 0 S(1) (2.12 µm) and found ∼80 sourcesin OMC-2 and OMC-3. These sources consist a dozen of collimated outflow aligned fromeast to west and with millimeter cores at their center. Based on the high condensation andlevel of outflow activity seen in H2 , they described that OMC-2 and OMC-3 are undergoinga “microburst” of star formation.

3.4. OPTICAL OBSERVATIONS

59

We further obtained the H2 image of OMC-3 with a better spatial resolution using the
University of Hawaii 88 inch (2.2 m) telescope and with a much higher sensitivity using theSubaru telescope in order to make it easier to identify the powering source of the outflows
in crowded regions. The details of analysis and result of these observations are discussed in
Sects. 8.2 and 8.3.

3.4

Optical Observations

3.4.1

Membership Studies with Proper Motion Measurements

Membership studies of OMC have been conducted mainly in the optical wavelength throughthe measurement of proper motions (Parenago 1954[148] ; Jones & Walker 1988[100] ; van Altena et al. 1988[193] ; McNamara et al. 1989[126] ). Tian et al. (1996)[183] examined the relative
proper motions and the membership probabilities for 333 sources with the plates taken overa period of 83 years in the Shanghai Observatory. 184 sources have higher membershipprobability than 70%, which they consider are the Orion members.

3.4.2

Detection of Circumstellar Disks

Two optical techniques were employed to identify sources with circumstellar disks in theseregions; one is by Hα emission and the other by U V excess (Fig. 3.6).
Herbig & Bell (1988)[83] compiled a catalog of 735 pre-main-sequence sources in OMC,
which were observed with the slit spectrograph or at equivalent resolution. The equivalent
width of Hα emission (EW [Hα ]) was measured for these sources, with which they wereclassified into cTTSs (EW [Hα ] > 10 Å) and wTTSs (EW [Hα ] < 10 Å).
Rebull et al. (2000)[160] surveyed the ONC flanking fields covering OMC-2 and OMC-3
with the U, V, and I bands. The purpose of this work is to determine the (U –V ) and(V –I ) colors of the Orion sources and to pick up sources with circumstellar disks based on
their U V excess emissions. About 5000 sources were examined for their colors and ∼230of them were found to have a U V excess of more magnitudes than 0.5 mag, a signature of
circumstellar disk. They also illustrated the consistency of this method to search for diskswith other better-established methods such as NIR excess or Hα emission.

60

CHAPTER 3. ORION MOLECULAR CLOUD 2 AND 3

ACIS-S2QUIRC (J,H,K)-4:55:00
ACIS-I-5:00:00

Bdecl. (J2000.0)

Ali & DePoy (1995)
05:00
Jones et al.(1994)
10:00

15:00

20:00
30

5:36:00

30
R.A. (J2000.0)

35:00

34:30

Figure 3.5: Past NIR observations of OMC-2 and OMC-3.
The gray scale represents the[199]), while the contours give the 1.3 mm intensity
continuum-subtracted H2 emission (Yu et al. 1997
[35]
(Chini et al. 1997 ). The pluses are the position of IRS 1–IRS 5 (Johnson et al. 1990[96] ). The survey fields of Jones et al. (1994)[101] and Ali & DePoy (1995)[2] are shown with thin lines. The FOVs ofobservations conducted in this thesis; Chandra, QUIRC J, H, and K band, and QUIRC H2 band (A, B, andC) are shown with thick lines (see Sect. 8.2).

3.4. OPTICAL OBSERVATIONS

61

In this thesis, we combine the NIR excess (this thesis; Tsujimoto et al. 2003[192] ), U V
excess (Rebull et al. 2000[160] ), and Hα emission line (Herbig & Bell 1988[83] ) data to discriminate sources with and without circumstellar disks. We recognize sources to have circumstellar
disks if they have at least one positive detection among these three methods.

ACIS-S2-4:55:00
ACIS-Idecl. (J2000.0)-5:00:00

05:00

10:00

15:00

20:00
30

5:36:00

30
R.A. (J2000.0)

35:00

34:30

Figure 3.6: Past optical observations of OMC-2 and OMC-3. squares: sources with the equivalent widthof Hα larger than 10 Å (Herbig & Bell 1988[83] ). Crosses: sources with U V excess (Rebull et al. 2000[160] ).
Pluses: sources with the membership probability of more than 70% (Tian et al. 1996[183] ). The contours
represent the 1.3 mm intensity (Chini et al. 1997[35] ). The Chandra FOVs are given in two oblique squares.

62

CHAPTER 3. ORION MOLECULAR CLOUD 2 AND 3

3.5

X-ray Observations

3.5.1

Surveys in the Soft X-ray Band

Two systematic X-ray studies of the Orion A were conducted by Gagné & Caillault (1994)[60]
and Gagné, Caillault, & Stauffer (1995)[61] with Imaging Proportional Counter (IPC) onboard the Einstein satellite and with High-Resolution Imager (HRI) onboard ROSAT (Fig. 3.7).
These observations provide the position and the count rate of 245 and 389 X-ray sourcesin a 4.5 square degree and a 0.8 square degree region, respectively. No spectroscopy has
been made in these observations. In Gagné, Caillault, & Stauffer (1995)[61] , X-ray emission
was found from sources of all spectral types, ranging from massive O- and B-type stars tolate-type pre-main-sequence sources. About 75 X-ray sources with a measured spectral typewere investigated for any relations between the X-ray luminosity (LX with an assumed Xray spectrum) and the bolometric luminosity (Lbol ), v sin i, rotation period, and the effective
temperature. They found that (1) LX is related to Lbol with LX /Lbol < 10−3 and (2) LX
and LX /Lbol do not appear to be related with the stellar rotation.
Geier, Wendker, & Wisotzki (1995)[64] observed the Orion region with Position-Sensitive
Proportional Counter (PSPC) onboard ROSAT and detected 171 X-ray sources. The purpose of this observation was to confirm the diffuse X-ray emission reported by Ku & Chanan(1979)[109] , but the trial was in vain because X-ray sources were too crowded. Unlike previous two detectors, PSPC has low-resolution spectral capability in the soft X-ray band
(0.1–2.4 keV), so they also conducted spectral analyses for bright 95 sources to determine
the plasma temperature and the interstellar absorption. Sources were separated into twogroups based on these parameters: (1) those with the absorption of NH < 2 × 1021 cm−2and the temperature of T ∼ 4 × 106 K (0.35 keV) and (2) those with the absorption of NH∼ 1022 cm−2 and the temperature of T ∼ 107 K (0.86 keV). The sources in the former groupare randomly distributed, while the latter are concentrated on the Trapezium cluster. These
results lead them to suspect that the former group consists of main sequence sources, while
the latter consists of YSOs.

3.5.2

Surveys in the Hard X-ray Band

Yamauchi et al. (1996)[196] studied the whole Orion A cloud with two pointing observations
with the ASCA satellite (Fig. 3.7). They detected 52 X-ray sources using Gas Imaging

3.5. X-RAY OBSERVATIONS

63

Spectrometer (GIS) and Solid-state Imaging Spectrometer (SIS). They also derived spectral
parameters of five bright X-ray sources. An interesting result was obtained that these X-ray
sources have a thin-thermal plasma of two temperatures; one is 0.7–1 keV and the other is 3–
5 keV. This was also confirmed in a composite spectra of many discrete sources accumulated
in large areas. This was the first hard X-ray imaging observation of the Orion region. In
addition to lower temperature plasma of 0.7–1 keV found by Einstein and ROSAT, higher
temperature plasma of 3–5 keV was first confirmed from discrete sources in the Orion.
Two important lessons can be drawn from these previous observations. First, we needto have the spatial resolution of ∼100 to resolve each X-ray source in star-forming regions like
OMC. Second, the hard X-ray capability is inevitable to overcome high extinction and to detect high temperature plasma. Preceding X-ray observatories such as Einstein, ROSAT, andASCA did not meet either of these requirements. We therefore made the X-ray observationon this region using the Chandra X-ray Observatory, which has ∼100 –500 spatial resolution
and hard X-ray imaging and spectroscopy capability (Tsujimoto et al. 2002a[189] ; this thesis).
The initial result of our Chandra observation was published by Tsuboi et al. (2001)[188] ,who concentrated on the hard X-ray detections from 1.3 mm cores in the northern part of
OMC-3. Two hard X-ray sources were detected at the protostellar cores with a thin-thermal
spectrum of NH = 1–3×1023 cm−2 and LX ∼ 1030 ergs s−1 . These protostellar cores are at
the class 0 stage based on their SEDs. They proposed that these X-ray emissions are thefirst candidates of X-ray-emitting class 0 sources.

64

CHAPTER 3. ORION MOLECULAR CLOUD 2 AND 3

ASCA/GIS (1)

40:00

ASCA/SIS (1)

50:00
ACIS-Sdecl. (J2000.0)-5:00:00

10:00
ACIS-I

20:00

ASCA/SIS(2)30:00
ASCA/GIS(2)5:38:00

30

37:00

30

36:00
30
35:00
R.A. (J2000.0)

30

34:00

30

00

30

00

(a) ASCA

40:00
ROSAT/HRI(3)50:00
ACIS-Sdecl. (J2000.0)-5:00:00

ROSAT/HRI(2)ACIS-I

10:00

20:00
ROSAT/PSPCROSAT/HRI(1)

30:00

5:38:00

30

37:00

30

36:00
30
35:00
R.A. (J2000.0)

30

34:00

(b) ROSAT

Figure 3.7: FOVs of the X-ray observations on OMC-2 and OMC-3. The past observations are shown inthin circles and squares, while the Chandra observation conducted in this thesis is in the thick squares.
The contours are the 1.3 mm intensity (Chini et al. 1997[35] ). (a) The FOVs of two ASCA observations (Yamauchi et al. 1996[196] ). (b) The FOVs of three ROSAT /HRI observations (Geier, Wendker,& Wisotzki 1995[64] ) and one ROSAT /PSPC observations (Gagné et al. 1995[61] ).

(cont.)X-ray . . . . . . . .

optical . . . . . . .

NIR–MIR . . . .

sub-millimeter

millimeter . . . .

centimeter . . .

IRTF, IRAM
NRO

imaging
imaging

13 CO

1.3 mmimaging
imaging
imaging
imaging

H2
J, H, K s
J, H, K s
J, H, K, L0 , H2
J, H, K, H2

imaging
imaging, spectroscopy
imaging

0.1–4.0 keV
0.1–2.4 keV
0.2–2.0 keV

imaging, spectroscopy

imaging

K

U, V, I

imaging

J, H, K

imaging

imaging

J, H, K, L

V

imaging
imaging, polarimetry

1.25–100µm

imagingpolarimetry

850µm
spectroscopy

imaging

C I, CO
1.6–20µm

imaging

450µm, 850µm

Kimaging

imagingCO

350µm

imaging

12 CO

imaging

imaging

H13 CO+ , HCO+ , COimaging

imaging

40–400µm

SEST

imaging

1.3mm

C I, C II

Effelsberg

imaging

NH3
13 CO, C18 O, C32 S, C34 S

ROSAT

ROSAT

Einstein

KPNO,WIYN

Shanghai

UH88

Subaru, IRTF

2MASS

2MASS

KPNO, CTIO

Perkins

KPNO

WIRO

IRTF, KAO

StewardWilson, HaleJCMT

Mt. Fuji

JCMT

CSO

KAO

LJO, KAO, MLO

BIMA

NRAO

NMA

IRAM

AT&T Bell Lab.

imaging
imagingCS
C18 O

AT&T Bell Lab.

VLA

imaging

3.6 cmVLA

observatory

imagingmode

3.6 cmbands/lines

Gagné et al. (1995)[61]Gagné, & Caillault (1994)[60]Geier et al. (1995)[64]Rebull et al. (2000)[160]

Tsujimoto et al. (2003)[192] (this thesis)
Tian et al. (1996)[183]Carpenter et al. (2001b)[28]
Tsujimoto et al. (2002b)[190] (this thesis)

Carpenter (2000)[26]

Ali & DePoy (1995)[2]Yu et al. (1997)[199]Johnson et al. (1990)[96]
Jones et al. (1994)[101]Thronson & Thompson (1982)[182]
Pendleton et al. (1986)[149]Matthews & Wilson (2000)[124]Gatley et al. (1974)[63]

Johnstone & Bally (1999)[99]
Ikeda et al. (1999)[94]

Lis et al. (1998)[117]Herrmann et al. (1997)[84]

Williams et al. (2003)[194]Thronson et al. (1978)[181]Yu et al. (2000)[200]Chini et al. (1997)[35]
Aso et al. (2000)[11]

Cesaroni & Wilson (1994)[31]Castets & Langer (1995)[30]

Dutrey et al. (1993)[45]Metzger et al. (1990)[129]Tatematsu et al. (1993)[179]Tsujimoto et al. (2002c)[191] (this thesis)
Bally et al. (1987)[14]

Reipurth et al. (1999)[162]reference

Table 3.3: Past observations of OMC-2 and OMC-3

3.5. X-RAY OBSERVATIONS
65

Chandraarea(arcmin2 )901472.........
512
OMC-2
Trapezium, OMC-2
Orion A, B, etc.
OMC-2, OMC-3

regionJ, H, KKJ, H, K s
J, H, K

band

Gagné & Caillault (1994)[60] . . . . . . . . . . .
Gagné et al. (1995)[61] . . . . . . . . . . . . . . . . .
Geier et al. (1995)[64] . . . . . . . . . . . . . . . . . .
Yamauchi et al. (1996)[196] . . . . . . . . . . . .
Tsujimoto et al. (2002)[189] (this thesis)

referencearea(arcmin2 )
16000
2900
1900
3900
360

band num. of(keV) sources
Einstein/IPC
0.1–4.0
245
ROSAT /HRI
0.2–2.0
389
ROSAT /HRI
0.1–2.4
171
ASCA/GIS, SIS 0.5–8.0
52
Chandra/ACIS 0.5–8.0
398

instrumentcompletenesslimita(mag)
∼14
∼14.5
∼14.8
∼16.0

num. ofsources2193548.......
1448

Tsujimoto et al. (2002a)[189] (this thesis)

Yamauchi et al. (1996)[196]Tsuboi et al. (2001)[188]reference

Table 3.5: Past X-ray survey studies of OMC-2 and OMC-3

a The 90% completeness limit in the K band, except for Carpenter (2000)[26] with the 94% limit.

Jones et al. (1994)[101] . . . . . . . . . . . . . . . . .
Ali & DePoy (1995)[2] . . . . . . . . . . . . . . . . .
Carpenter (2000)[26] . . . . . . . . . . . . . . . . . . .
Tsujimoto et al. (2003)[192] (this thesis)

reference

imaging, spectroscopy

0.5–8.0 keV

ASCA

observatory

Table 3.4: Past NIR survey studies of OMC-2 and OMC-3

imaging, spectroscopy

mode

0.5–8.0 keVbands/lines

66
CHAPTER 3. ORION MOLECULAR CLOUD 2 AND 3

Chapter 4
Observing Facilities and Instruments
Contents
4.1

4.2

4.3

4.4

4.5

Chandra X-ray Observatory . . . . . . . . . . . . . . . . . . . . .

68

4.1.1

Spacecraft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

68

4.1.2

Optics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

69

4.1.3

Instrument (ACIS) . . . . . . . . . . . . . . . . . . . . . . . . . . .

73

University of Hawaii 88 inch (2.2 m) Telescope . . . . . . . . .

79

4.2.1

Telescope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

79

4.2.2

Instrument (QUIRC) . . . . . . . . . . . . . . . . . . . . . . . . . .

82

Subaru Telescope. . . . . . . . . . . . . . . . . . . . . . . . . . .

83

4.3.1

Telescope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

83

4.3.2

Instrument (IRCS) . . . . . . . . . . . . . . . . . . . . . . . . . . .

83

Infrared Telescope Facility . . . . . . . . . . . . . . . . . . . . . .

85

4.4.1

Telescope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

85

4.4.2

Instrument (NSFCam) . . . . . . . . . . . . . . . . . . . . . . . . .

85

Very Large Array . . . . . . . . . . . . . . . . . . . . . . . . . . .

87

4.5.1

Telescope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

87

4.5.2

Radio Interferometry . . . . . . . . . . . . . . . . . . . . . . . . . .

89

67

68

CHAPTER 4. OBSERVING FACILITIES AND INSTRUMENTS

In this chapter, we review on all telescopes and instruments that we used for this thesis.
The first section is devoted for the Chandra X-ray observatory (Sect. 4.1), where we mention
the basic features of the spacecraft, optics, and detectors. For detectors, ACIS onboard
Chandra, which we actually used, is particularly focused. The following three sections are
for NIR telescopes and instruments; QUIRC on the University of Hawaii 88 inch (2.2 m)
telescope (Sect. 4.2), IRCS on the Subaru telescope (Sect. 4.3), and NSFCam on IRTF
(Sect. 4.4). The last section deals with VLA (Sect. 4.5). Along with the properties of thearray, the basic idea of radio interferometry is briefly reviewed.

4.1

Chandra X-ray Observatory

4.1.1

Spacecraft

The Chandra X-ray Observatory was successfully launched in July 1999 by National Aeronautics and Space Administration (NASA). The spacecraft circulates around the earth oncein 64 hours on an elliptical orbit with the perigee and the apogee distance of 10000 km
and 140000 km, respectively. It is comprised of several modules, including the solar panels,
the mirror assembly, the telescope, and the integrated science instrument module (Fig. 4.1).
Details of Chandra can be found in the Chandra Proposers’ Observatory Guide (2001)[32] .

Figure 4.1: Schematic view of the Chandra spacecraft (Chandra Proposers’ Observatory Guide 2001[32] ).

The pointing accuracy of the spacecraft, which is measured and stabilized by the Point-4.1. CHANDRA X-RAY OBSERVATORY

69

ing Control and Aspect Determination (PCAD) system, is ∼0.100 s−1 . The Chandra lineof-site is kept dithered during observations drawing a Lissajous pattern. The dithering
distributes photons over many detector pixels for several purposes; to prevent a bad pixel toruin the entire observation, to reduce uncertainty due to pixel-to-pixel variations in the quantum efficiency, to pick up sources in the gaps between CCD chips, and to allow sub-samplingof the image.

4.1.2

OpticsMirror AssemblyHigh Resolution Mirror Assembly (HRMA) is the mirror assembly carried on Chandra. It
consists of a nested set of four paraboloid-hyperboloid (Wolter-1) grazing-incidence X-ray
mirror pairs, with the focal length of ∼10 m and the largest mirror having a diameter of∼1.2 m (Fig. 4.2). The most precisely shaped and aligned, and the smoothest X-ray mirrors
ever constructed allow Chandra to obtain unprecedentedly sharp X-ray images.

Figure 4.2: Configuration of four nested mirror pairs (Chandra Proposers’ Observatory Guide 2001[32] ).

70

CHAPTER 4. OBSERVING FACILITIES AND INSTRUMENTS

Effective Area
The on-axis effective area of HRMA is shown in Figure 4.3, together with the expected effective areas when the detector quantum efficiency is convolved. The effective area decreases
as the increasing off-axis angle (the vignetting effect; Fig. 4.4) depending on the energy.

Figure 4.3: Energy dependence of the on-axis effective area of HRMA (solid curve). The expected effective
areas convolved with the detector quantum efficiency are separately shown with dotted (front-illuminated
ACIS), dashed (back-illuminated ACIS), dashed-and-dotted (HRC-I), and dashed-and-triplicated-dotted(HRC-S) curves (Chandra Proposers’ Observatory Guide 2001[32] ).

Point Spread Function
The point spread function (PSF) is a spatial distribution function over the detector surface
of incident X-ray photons at a given energy. The PSF is approximately shaped Gaussian.
The sharpness of images is evaluated either by the full width half maximum (FWHM) or theencircled energy radius of PSFs. A circle of 50% encircled energy radius, which equals tothe half of FWHM if the PSF is exactly Gaussian, accumulates the 50% of incident photons.
Figure 4.5 gives the on-axis PSF, while Figure 4.6 shows the dependence of PSFs on theoff-axis angle.

4.1. CHANDRA X-RAY OBSERVATORY

71

Figure 4.4: Spatial dependence of the effective area as a function of off-axis angle for several representative
incident X-ray energies (Chandra Proposers’ Observatory Guide 2001[32] ).

Figure 4.5: On-axis PSFs of several representative incident X-ray energies as a fraction of the encircled
photons (energy) inside the circle with a given radius (Chandra Proposers’ Observatory Guide 2001[32] ).

72

CHAPTER 4. OBSERVING FACILITIES AND INSTRUMENTS

Figure 4.6: The 50% and 90% encircled energy radii at a given off-axis angle. The four panels give theradii of representative incident X-ray energies separately for ACIS-I0, -I1, -I2, and -I3 (Chandra Proposers’
Observatory Guide 2001[32] ).

4.1. CHANDRA X-RAY OBSERVATORY

4.1.3

73

Instrument (ACIS)

Configuration
Ten X-ray CCDs comprise the Advanced CCD Imaging Spectrometer (ACIS) array (Fig. 4.7).
The array consists of two parts; ACIS-I with 2×2 CCDs (ACIS-I0, -I1, -I2, and -I3) and
ACIS-S with 1×6 CCDs (ACIS-S0, -S1, -S2, -S3, -S4, and -S5), which are mainly used forthe imaging-spectroscopic and the grating-spectroscopic purposes, respectively. The format
of CCD chips is 1024×1024 pixels with the pixel scale of 0.49200 pixel−1 . All CCDs utilize
front-illuminated CCDs except for ACIS-S1 and ACIS-S3 that are back-illuminated CCDs.

ACIS FLIGHT FOCAL PLANE
not constant with Z~22 pixels ~11"22 pixels
= 11"

I0

I1

w203c4r
0

w193c2
1
x

I2

}

I3

w158c4r

w215c2r

2

3

ACIS-I(aimpoint on I3 = (962, 964))

330 pixels = 163"
S0

S1

S2

w168c4r
4

w140c4r
5

w182c4r
6

S3+
w134c4r
7

S4S5

w457c48

w201c3r
9}

ACIS-S(aimpoint on S3 = (252, 510))+∆Y
18 pixels = 8".8

Image Region

Bottom.

column

three

two

one

BI chip indicator

node zero

+Z
Top

.

row

TargetOffsetCoordinates+Z
Pointing+∆Z

Coordinates-Z

Pixel (0,0)+Y

Sim Motion

Frame StoreCCD Key

NodeDefinitions

Row/Column
Definition

Coordinate
Orientations

Figure 4.7: Configuration of the ACIS array. The top two panels show the ACIS-I and ACIS-S arrays,
while the schematic view of each CCD chip is given at the bottom panel. In our observation, ACIS-I0, I1, I2,
I3 and S2 were used with the aim point on the cross at the top left corner of ACIS-I3 (Chandra Proposers’
Observatory Guide 2001[32] ).

74

CHAPTER 4. OBSERVING FACILITIES AND INSTRUMENTS

Energy Resolution
An X-ray CCD can work as a medium-resolution (E/∆E = 10–50) spectrometer as well as
an imager. When an incident X-ray photon with the energy of E keV is photoelectricallyabsorbed by silicon atoms in the depletion layer of the device, it emits a photoelectron withthe corresponding kinematic energy. The photoelectron keeps ionizing other atoms until
all energy is consumed, which finally produces n = E/W electrons where W keV is theaverage energy required to ionize an atom. By measuring n with the device, the incident
X-ray energy is determined on a photon basis. The energy resolution is determined by the
convolution of the Poisson fluctuation of n and the readout noise (Fig. 4.8). In case of silicon(W = 3.65 keV), the lower limit of the energy resolution is ∼120 eV at 6 keV.

Figure 4.8: Pre-launch energy resolution of front-illuminated (solid ), back-illuminated S1 (dotted ), and S3(dashed ) chips (Chandra Proposers’ Observatory Guide 2001[32] ).

Unfortunately, the CCD chips onboard Chandra were damaged by charged particles on
the orbit, degrading the energy resolution of ACIS. This is currently handled by lowering
the temperature of the device to –110◦ C (as of our observation date) and by introducing a
new set of detector response functions.

4.1. CHANDRA X-RAY OBSERVATORY

75

Effective Energy Range
Three factors are convolved to determine the energy range that an ACIS observation issensitive to. The first factor is the quantum efficiency of the CCD chip itself. At higher
energies, the efficiency is constrained by the thickness of the depletion layer, where X-ray
photons with higher energy are more difficult to be photoelectrically absorbed. At lower
energies, on the other hand, the efficiency is reduced by the absorption of X-ray photons byelectrodes and insulators on the surface of the device. This makes back-illuminated chips tohave higher quantum efficiency at lower energies than front-illuminated ones. The second
factor is the transmission of the optical blocking filters (OBFs). ACIS has three OBFs
with the thickness of 2000 Å (thick), 1200 Å (medium), and 400 Å (thin) to block photons
in the optical wavelengths. Filters are composed of polyimide (a poly-carbonate plastic)
sandwiched between two thin layers of aluminum. The third is the effective area of HRMA,
which depends on the incident X-ray energy. Figure 4.9 shows the effective area of all thesefactors combined. In our observation, we used front-illuminated CCDs with the medium
thickness filter, making our observation sensitive to X-ray photons in the 0.5–8.0 keV energy
range.

Background Events
The background events of ACIS are dominated by two components; cosmic ray (CR) eventsand the cosmic X-ray backgrounds (CXB). The CR events are reduced by various filtering
procedures, including the grade filtering and the elimination of flaring events caused by CRs.
A typical background spectrum after these procedures is given in Figure 4.10. The CR eventsare dominant in the lower energy band than 5 keV, while CXB in the higher energy band.
The average count rate of this background spectrum is shown for some representative energy
ranges (Table 4.1). The background count rate is roughly constant within a period of thesame CCD temperature (Fig. 4.11). Unlike CXB, the rate of CR events also depend on theposition on the chip (Fig. 4.12) by a factor of ∼20%.

Other Detectors
High-Resolution Imager (HRI) is another focal plane instrument. HRI is comprised of two
imaging detectors using micro-channel plates; High Resolution Camera (HRC)-I designed

76

CHAPTER 4. OBSERVING FACILITIES AND INSTRUMENTS

Figure 4.9: Expected effective area of ACIS with the dotted (front-illuminated chips) and the solid (backilluminated chips) curves. The quantum efficiency, the filter transmission, and the effective area of the opticalsystem are all combined (Chandra Proposers’ Observatory Guide 2001[32] ).

4.1. CHANDRA X-RAY OBSERVATORY

77

Figure 4.10: Background spectra of the back-illuminated ACIS-S3 chip (the upper spectrum) and the frontilluminated ACIS-I3 (the lower spectrum) chip. The spectra, containing both the CR and CXB components,
are extracted from the whole relevant chips from the September 1999 – January 2000 data. The events withbad grades, bad pixels and bright celestial sources are eliminated (Markevitch 2001[121] ).

78

CHAPTER 4. OBSERVING FACILITIES AND INSTRUMENTS

Figure 4.11: Long-term variation of background count rates of ACIS. The top panel shows the count rateof 0.3–5 keV that represents the CR component, while the bottom shows the rate of 5–10 keV that represents
CXB. The CCD temperature is given at each period (Markevitch 2001[121] ).

4.2. UNIVERSITY OF HAWAII 88 INCH (2.2 M) TELESCOPE

79

Table 4.1: Background count rate (s−1 ) of Chandra
ACIS chips for five representative energy ranges (Markevitch 2001[121] ). The rates in 0.5–8 keV were estimatedusing these values and the standard background spectrum(Figure 4.10).

chip
0.3–10 keV
0.5–2 keV
0.5–7 keV
5–10 keV
10–12 keV
0.5–8 keV

I2a
0.321
0.083
0.196
0.153
0.087
0.226

I3a
0.310
0.076
0.188
0.154
0.087
0.220

S1b
S2a
S3b
1.483 0.336 0.857
0.168 0.086 0.160
0.454 0.207 0.375
1.038 0.162 0.506
0.674 0.081 0.603. . . . . 0.239 . . . . .

a Front-illuminated chips.
b Back-illuminated chips.

for wide-field imaging and HRC-S designed to serve as a readout for the Low Energy Transmission Grating (LETG). HRI has no spectral resolution, but provides better temporal
resolution than ACIS.
Each of the two instruments (ACIS and HRI) can be combined with one of the two
gratings to conduct high-resolution (E/∆E ∼ 100–1000) spectroscopy. High Energy Transmission Grating (HETG) and LETG are respectively optimized for grating spectroscopy ofthe high and low energy X-rays.

4.2

University of Hawaii 88 inch (2.2 m) Telescope

4.2.1

Telescope

The University of Hawaii 88 inch (2.2 m) telescope (UH88) is one of the telescopes at thesummit of Mauna Kea, Hawaii, U.S.A. It was constructed in 1970 and has been underoperation of the University of Hawaii. The telescope utilizes the Ritchey-Crétien optics
system and has the Cassegrain focus. The primary mirror has a diameter of 88.13 inch
(2.24 m) with the focal length of 22.50 m (Fig. 4.13).

80

CHAPTER 4. OBSERVING FACILITIES AND INSTRUMENTS

Figure 4.12: Spatial dependence of the background count rate of ACIS-I0. The profiles on the x-axis(dotted ) and y-axis (solid ) are shown. The count rate in the 5–10 keV range is used, where the CR component
is dominant. The CXB component has no spatial dependence (Markevitch 2001[121] ).

4.2. UNIVERSITY OF HAWAII 88 INCH (2.2 M) TELESCOPE

81

Figure 4.13: Schematic view of the University of Hawaii 88 inch (2.2 m) telescope. QUIRC is mounted on
the Cassegrain focus of the telescope.

82

CHAPTER 4. OBSERVING FACILITIES AND INSTRUMENTS

4.2.2

Instrument (QUIRC)

Quick Infrared Camera (QUIRC; Hodapp, Hora, & Metzger 1997[89] ) is the only NIR camera mounted on the Cassegrain focus of the telescope. QUIRC has a HAWAII (HgCdTe
Astronomical Wide Area Infrared Imaging) array produced by Rockwell Science Center. It
consists of four quadrants, each of which has the format of 512×512 pixels with the pixel sizeof 18.5 µm×18.5 µm. It has two optics with different focal lengths (f /10 and f /31), whichyields the pixel scale of 0.188600 pixel−1 and 0.060800 pixel−1 , and the FOV of 19300 ×19300 and
6200 ×6200 , respectively. In our observation, we used the f /10 optics to maximize FOVs.
QUIRC is sensitive to the radiation from 1 µm to 2.5 µm. Two filter wheels witheight positions are combined to observe either in the broad-band (J, H, K, K s , K0 , andHK0 ) or in the narrow-band (H2 v = 1 − 0 S(1) , Fe II, CO band head, Br γ, and theirneighboring continuum). We used three broad-band (J, H, and K ) and two narrow-band(H2 v = 1 − 0 S(1) at 2.12 µm and K-continuum at 2.26 µm) filters. The transmissions ofthese filters are given in Figure 4.14.
The effective gain of the detector is 1.85 electrons ADU−1 and the linearity is kept
better than 1% for values up to ∼44000 ADUs. The average detector dark current is ≤0.8 electrons s−1 and the readout noise is ≤ 15 electrons (r.m.s.). The camera sensitivity is∼18.6 mag (J band), ∼17.8 mag (H band), and ∼16.2 mag (K band), assuming one minuteon-source integration time, a PSF of 0.500 FWHM, and 5 σ detection.

Table 4.2: Comparison of NIR imagers used in this thesis

telescopes . . . . . . . . . . .
instruments . . . . . . . . .
format (pixels) . . . . . .
pixel scale (00 pixel−1 )FOV (00 ) . . . . . . . . . . . . .
filters used . . . . . . . . . .
sensitivity (mag)a. . . . .

UH88Subaru
IRTF
QUIRC
IRCS
NSFCam1024×1024
1024×1024
256×256
0.189
0.058
0.15
193×193
59.4×59.4
76.8×76.8
J, H, K, H2 , K -cont. J, H, K, H2 , K -cont.
L0
∼16
∼18
∼17

a The 5 σ detection limit in the K band with one minute on-source integration time.

4.3. SUBARU TELESCOPE(a) broad-bands

83(b) narrow-bands

Figure 4.14: Transmissions of QUIRC filters; (a) broad-band and (b) narrow-band filters.

4.3

Subaru Telescope

4.3.1

Telescope

The Subaru telescope is also at the summit of Mauna Kea. It celebrated the first light inearly 1999 and has been operated by National Astronomy Observatory of Japan (NAOJ).
The telescope has the alto-azimuth mounting with four foci; the prime focus, the Cassegrain
focus, and two Nasmyth foci for optical and infrared detectors (Fig. 4.15). It has the largest
primary mirror among all the single mirrors facilitated in the telescopes around the world,with the diameter of 8.2 m and the focal length of 15 m.

4.3.2

Instrument (IRCS)

Infrared Camera and Spectrograph (IRCS) is a NIR imager and spectrometer for wide variety
of usage (Tokunaga et al. 1998[184] ; Kobayashi et al. 2000[105] ). It has two ALADDIN II
1024×1024 pixel InSb arrays; one is for the imaging and the grism spectroscopy and the

84

CHAPTER 4. OBSERVING FACILITIES AND INSTRUMENTS

Figure 4.15: Schematic view of the Subaru telescope. IRCS is mounted on the Cassegrain focus of thetelescope.

4.4. INFRARED TELESCOPE FACILITY

85

other for the echelle spectroscopy observations.
As an imager, it has two pixel scales of 0.05800 pixel−1 and 0.02300 pixel−1 with thecorresponding FOV of 59.400 ×59.400 and 23.600 ×23.600 . They are optimized to be used withthe tip-tilt and adaptive optics, respectively. The detector is sensitive at 0.9–5.5 µm with thefilters of J, H, K 0 , K, L0 , and M0 for the broad-band, and Fe II, Br α, Br γ, H2 v = 1 − 0 S(1),
2–1 S(1), etc. and their neighboring continuum for the narrow-band. The transmissions ofbroad-band filters are shown in Figure 4.16.
The detector gain is 12.2 electrons ADU−1 and the linearity is kept up to ∼136000 ADUs.
The dark current and the readout noise are 0.2–0.3 electrons s−1 and 67 electrons (r.m.s.),respectively. We used non-destructive readouts to decrease readout noise. The camera
attains J ∼ 23.6 mag, H ∼ 22.8 mag, and K ∼ 22.3 mag with one-hour integration time,a PSF of 0.500 FWHM, and 5 σ detection. In this observation, we used the ALLADIN II
for the camera array, which was replaced with the ALLADIN III array with much superiorsensitivity in September 2001.
IRCS camera also serves as a grism spectrograph providing a spectral resolving power of
R = 100–2000. IRCS also has a separated echelle spectrograph providing a spectral resolving
power of R = 5000–20000.

4.4

Infrared Telescope Facility

4.4.1

Telescope

The Infrared Telescope Facility (IRTF) is located at the summit of Mauna Kea. It is constructed in 1979 and is operated for NASA by the University of Hawaii. IRTF is optimized
for NIR observations. It has the primary mirror of the 3.0 m in aperture and the Cassegrain
focus.

4.4.2

Instrument (NSFCam)

NSFCam (Leggett & Denault 1996[115] ) is a NIR camera mounted on the Cassegrain focusof the telescope. It employs an InSb array with the format of 256×256 pixels. Threedifferent magnifications can be selected that respectively yield the pixel scale of 0.300 pixel−1 ,86

CHAPTER 4. OBSERVING FACILITIES AND INSTRUMENTS

Figure 4.16: Broad-band filter transmissions of the Mauna Kea system advocated by Tokunaga, Simons,& Vacca (2002)[186] . Subaru IRCS and IRTF NSFCam comply with the system.

4.5. VERY LARGE ARRAY

87

0.1500 pixel−1 and 0.0600 pixel−1 with the corresponding FOVs of 76.800 ×76.800 , 37.900 ×37.900 ,and 14.100 ×14.100 .
NSFCam has the sensitivity in 1–5 µm. By rotating its filter wheel, broad-band (J, H,
K, K 0 , L, L0 , and M ) and narrow-band (He I, Fe II, H2 v = 1 − 0 S(1), v = 2 − 1 S(1),CO band-head and their neighboring continuum) filters can be selected. We obtained theL0 -band images with the pixel scale of 0.300 pixel−1 to complement the J -, H -, and K -band
images taken with the Subaru telescope. The filters also comply with the Mauna Kea filter
system (Fig. 4.16).
The camera can detect J ∼ 20.6 mag, H ∼ 18.9 mag, K ∼ 18.8 mag, and L0 = 13.6 magwith one-minute integration time, an aperture of 200 ×200 box, and 3 σ detection.

4.5

Very Large Array

4.5.1

Telescope

Very Large Array (VLA) is the radio interferometer on Plains of San Agustin, New Mexico,
U.S.A. It celebrated its first fringe in February 1976 and has been operated by National
Radio Astronomy Observatory (NRAO). The interferometer consists of 27 antennae, whichcollaborate together for interferometry observations. The antennae have the size of 25 m indiameter and are positioned in the “Y” shape with nine antennae on each arm (Fig. 4.17).
Four configurations (A, B, C, and D) with different arm lengths are available and theconfiguration changes once in four months. The longer arm length configurations have longer
baselines (distances between two antennae), thus have higher spatial resolution but are lesssensitive to extended structures (Table 4.3). At the Cassegrain focus of each antenna, receivers in eight frequency bands are equipped (Table 4.4). Our observation was performed
in 3.6 cm with the A configuration. Details on the radio interferometry and VLA can befound in Clark (1999)[36] , Thompson (1999)[180] , Napier (1999)[140] , Rommey (1999)[166] , andPerley & Taylor (2002)[151] .

88

CHAPTER 4. OBSERVING FACILITIES AND INSTRUMENTS

Figure 4.17: Configuration of VLA. The 27 antennae are laid out in the “Y” shape with the appropriate
spacing to optimize the efficiency of u − v coverage.

Table 4.3: VLA configurations

configuration . . . . . . . . . . . . . . .
A
BCDmin. baseline (km) . . . . . . . . . 0.68 0.21 0.035 0.035
max. baseline (km) . . . . . . . . 36.4 11.4
3.4 1.03
00 asynthesized beam width ( )0.24 0.7
2.3
8.4
a The half power beam width at 3.6 cm.

4.5. VERY LARGE ARRAY89

Table 4.4: VLA frequency bands

band
4
P
L
C
X
U
K
Q

frequency
wavelength resolutiona
(Hz)
(cm)
(00 )
0.073–0.0745
400
24.0
0.30–0.34
90
6.0
1.34–1.73
20
1.4
4.5–5.06
0.4
8.0–8.8
3.6
0.24
14.4–15.4
2
0.14
22–24
1.3
0.08
40–50
0.7
0.05

a The synthesized beam width of the A configuration.

4.5.2

Radio Interferometry

Let us suppose that the surface brightness of a celestial source is ²ν (R) at the position of R
and at the frequency of ν. The quasi-monochromatic component of the electric field that we
receive at the position of r can be expressed as
ZEν (r) =S

dR ²ν (R)exp(2πiν|R − r|/c),|R − r|(4.1)

by integrating ²ν (R) over the source region (S). The spatial coherence function is definedas the product of Eν (r) at two different positions (r1 and r2 );Vν (r1 , r2 ) = < Eν (r1 )Eν (r2 ) >
¿Z

=

Z

S

Ã

×

dR1

dR2 ²ν (R1 )²∗ν (R2 )S

exp (2πiν|R1 − r1 |/c)
|R1 − r1 |!Ã

exp (−2πiν|R2 − r2 |/c)
|R2 − r2 |

!+

.

(4.2)

The surface brightness of the celestial source can be assumed to be coherent with eachother at different positions with < ²(R1 )²(R2 ) >∝ δ(R1 − R2 ). We can make a further
approximation of 1/|R − r| ≈ 1/|R| to transform the spatial coherence function intoZVν (r1 , r2 ) =SdΩ Iν (s) exp (−2πiνs · (r1 − r2 )/c),

(4.3)

90

CHAPTER 4. OBSERVING FACILITIES AND INSTRUMENTS

where s = R/|R|, dR = |R|2 dΩ, and Iν (s) = |R|2 < |²ν (s)|2 >. We introduce a new
metric so that r1 − r2 = λ(u, v, w) in order to measure lengths in the unit of the wavelength;
λ = c/ν. By setting the w-axis in the direction of r1 × r2 , w = 0. Then,Z

Z

Vν (u, v) =

du

0

Z

dv 0 Iν (u0 , v 0 )exp (−2πi(uu0 + vv 0 ))

Z

du0

≈

q

(1 − u02 − v 02 )dv 0 Iν (u0 , v 0 ) exp (−2πi(uu0 + vv 0 )).

(4.4)

q

Here, (1 − u02 − v 02 ) ≈ 1 is assumed for simplicity. By considering the vignetting effectAν (u0 , v 0 ) of the telescope,ZVν (u, v) =

Z

du

0

dv 0 Aν (u0 , v 0 )Iν (u0 , v 0 ) exp (−2πi(uu0 + vv 0 )).

(4.5)

The surface brightness distribution of the source Iν (u, v) is thus derived by Fourier-convertingVν (u, v).
When the spatial coherence function is applied to the simplest interferometer with twoantennae at r1 and r2 , the visibility function is obtained asV= |V | exp (iφ)

(4.6)

Z

=

S

dΩ A(s0 )I(s0 ) exp (−2πiνb · s0 /c),

(4.7)

where b = r1 − r2 is the baseline vector in the u-v plane and s0 = s − s0 with s0 being theunit vector pointing at the phase tracking center.
The value of the visibility function over the u-v plane can be obtained through thecorrelater outputs. The correlater multiplies the voltages from two antennae (V1 (t) andV2 (t)) and integrates it for a given period of time (T ). As V1 (t) and V2 (t) have different
phases stemming from their geometrical distance to the source;
V1 (t) = V1 cos (2πν(t − b · s/c)

(4.8)

V2 (t) = V2 cos (2πνt).

(4.9)

The correlater output is described asr

1ZT
dt V1 (t)V2 (t)T 0−→ V1 V2 cos (2πνb · s/c)∝

(T −→ ∞)

(4.10)

4.5. VERY LARGE ARRAY

91

phase tracking centerw'v'
I(u',v')
u'
dΩ

v
w
u
s
so
bs0
antenna 1bantenna 2

correlatorr
Figure 4.18: Schematic view of the radio interferometry (Rohlfs & Wilson 1999[165] ).

92

CHAPTER 4. OBSERVING FACILITIES AND INSTRUMENTS

The output is also proportional to the power that an antenna receives; A(s)I(s)∆ν∆Ω.
Therefore, by integrating s over the antenna beam width, the correlater output isZ

r = ∆νS

A(s)I(s) cos (2πνb · s/c)

(4.11)

When we substitute s with s0 + s0 , we obtainZr = ∆ν cos (2πνb · s0 /c)SdΩ A(s0 )I(s0 ) cos (2πνb · s0 /c)Z−∆ν sin (2πνb · s0 /c)SdΩ A(s0 )I(s0 ) sin (2πνb · s0 /c)(4.12)The real and imaginary part of the visibility function;Z<[V ] = |V | cos (φ) =dΩ A(s0 )I(s0 ) cos (2πνb · s0 /c)

SZ=[V ] = |V | sin (φ) = −SdΩ A(s0 )I(s0 ) sin (2πνb · s0 /c)(4.13)(4.14)(4.15)

appears in r, which connects r and V asr = ∆ν|V | cos (2πνb · s0 /c − φ).

(4.16)

By measuring the amplitude and the phase of r, the value of the visibility function is derived
at a given point of the u-v plane. With N antennae, N C2 correlations can be obtained,
which are all used to derive the value of the visibility function at N C2 points. These points
move around the u-v plane as the earth rotates and s0 changes from time to time. The
visibility function V (u, v) is obtained after gridding the data points over the u-v plane, thenis Fourier-converted to derive the surface brightness distribution.

Chapter 5
Chandra and QUIRC Observations
Contents
5.1

5.2

X-ray Observation with Chandra/ACIS . . . . . . . . . . . . . .

94

5.1.1

Observation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

94

5.1.2

Data Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

94

5.1.3

Source Extraction . . . . . . . . . . . . . . . . . . . . . . . . . . .

96

5.1.4

2MASS Counterpart of Chandra Sources . . . . . . . . . . . . . . .

96

5.1.5

Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

NIR Observation with UH88/QUIRC . . . . . . . . . . . . . . . 104
5.2.1

Observation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

5.2.2

Data Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

5.2.3

Source Extraction and Photometry . . . . . . . . . . . . . . . . . . 107

5.2.4

2MASS Counterpart of QUIRC Sources . . . . . . . . . . . . . . . 109

5.2.5

Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

5.2.6

QUIRC Counterpart of Chandra Sources . . . . . . . . . . . . . . . 114

93

94

CHAPTER 5. CHANDRA AND QUIRC OBSERVATIONSIn this chapter, we describe our X-ray and NIR observations on OMC-2 and OMC-3, andtheir data reduction and results. We conducted a deep-exposure Chandra/ACIS observationand detected ∼400 X-ray sources in this field. These X-ray sources were first correlated withthe 2MASS catalog to identify the NIR counterpart (Sect. 5.1). The 2MASS catalog, which
covers brighter NIR sources than K = 14 mag, was found not to be deep enough to matchthe Chandra depth. In order to complement 2MASS with fainter sources, we made a followup NIR observation deeper on the Chandra field (Sect. 5.2) using QUIRC mounted on the
University of Hawaii 88 inch (2.2 m) telescope. The Chandra sources that have no 2MASS
counterpart were further correlated with the QUIRC sources to find their NIR counterpart.
The X-ray and NIR source lists are separately given in Tables A.1 and B.1.

5.1

X-ray Observation with Chandra/ACIS

5.1.1

Observation

The Chandra observation on OMC-2 and OMC-3 was carried out on January 1–2, 2000
with a nominal exposure time of 88.4 ks. We used the four ACIS-I chips (I0, I1, I2, andI3) and one ACIS-S chip (S2) on the focal plane of the mirror system. The four ACIS-I
chips cover a field of ∼170 ×170 and the ACIS-S chip of ∼8.50 ×8.50 . The nominal center was
set at R.A. (right ascension) = 05h 35m 20.792s and decl. (declination) = –05◦ 050 46.9500 (theequinox J2000.0) so that the ACIS-I FOV covers the whole OMC-2 and OMC-3 (Fig. 5.1).
The timed exposure mode was used as the operating mode with the frame time of 3.2 s.

5.1.2

Data Reduction

For data reduction, we used the level 2 data “reprocessed” at the Chandra X-ray Center(CXC). This version improves the aspect solution and restores the degradation of the energy
gain and resolution due to the increase of the charge transfer inefficiency (CTI) of ACIS1 .
We also applied the acis process events program to the data in order to eliminate “spikings”
in X-ray spectra reported by CXC2 . For data manipulation, we used CIAO version 2.23 and1

See http://asc.harvard.edu/udocs/reprocessing.html.
See http://asc.harvard.edu/ciao/caveats/acis pi.html.
3
See http://asc.harvard.edu/ciao/.
2

5.1. X-RAY OBSERVATION WITH CHANDRA/ACIS

95

50:00
ACIS-S2

55:00

ACIS-Idecl. (J2000.0)-5:00:00

05:00

10:00

15:00

30

5:36:00

30
R.A. (J2000.0)

35:00

34:30

Figure 5.1: FOV of Chandra. The larger and smaller squares indicate the FOVs of ACIS-I and ACISS2, respectively. The aim point is shown with the cross. The contours are the 1.3 mm intensity(Chini et al. 1997[35] ).

96

CHAPTER 5. CHANDRA AND QUIRC OBSERVATIONSHEAsoft version 5.24 . Throughout this thesis, we used X-ray photons in the 0.5–8.0 keVenergy band unless otherwise noted. Photons of each source were accumulated from anelliptical region. The major and minor axis lengths and the position angles were derived
from the wavdetect program. For some sources with bright neighbors, we manually shifted
their accumulation region to avoid contamination. Background photons were accumulated
from the standard background data provided by the ACIS team5 , which combine someobservations of relatively empty fields at high galactic latitudes. The pseudo-color image isshown in Figure 5.2. The Chandra PSF radius increases as the off-axis angle becomes larger(Fig. 4.6), which causes off-axis sources to appear extended.

5.1.3

Source Extraction

For source detection, we used the wavdetect program with the significance threshold of
1×10−5 (one false recognition of event pixels is expected in a 105 pixel image) and the√wavelet scales ranging from 1 to 16 pixels in multiples of 2. We removed spurious sources
through careful inspection by eye. We then detected 365 sources in the 0.5–8.0 keV band
image (I1–I354 from ACIS-I and S1–S11 from ACIS-S). In order to pick up either highly
absorbed (hard) or less absorbed (soft) sources more effectively, we also applied the samedetection algorithm to the 2.0–8.0 keV (hard) and 0.5–2.0 keV (soft) band images. Then, 17(I355–I369 and S11-S12) and 16 (I370–I385) sources were additionally found, respectively. In
total, we detected 398 Chandra sources in the ACIS-I and ACIS-S FOVs. For each detectedsource, we calculated the X-ray photon counts (0.5–8.0 keV) and the hardness ratio (HR),which is defined as (H − S)/(H + S), where H and S are the photon counts in the hard andsoft band, respectively (Table A.1).

5.1.4

2MASS Counterpart of Chandra Sources

2MASS Database
The Two Micron All Sky Survey (2MASS)6 is a joint project among NASA Infrared Processing and Analysis Center (IPAC), Jet Propulsion Laboratory (JPL), the University of4

See http://heasarc.gsfc.nasa.gov/docs/software/lheasoft/.
See http://cxc.harvard.edu/contrib/maxim/bg/index.html.
6
See http://www.ipac.caltech.edu/2mass/ for more details.
55.1. X-RAY OBSERVATION WITH CHANDRA/ACIS

97

50:00

55:00

decl. (J2000.0)-5:00:00

05:00

10:00

15:00

30

5:36:00

30
R.A. (J2000.0)

35:00

Figure 5.2: Three-color image of Chandra observations. Red, green, and blue are for photons in the
0.2–1.0 keV, 1.0–2.5 keV, and 2.5–8.0 keV, respectively.

98

CHAPTER 5. CHANDRA AND QUIRC OBSERVATIONS

Massachusetts, and California Institute of Technology (CIT), which aims to provide imaging data of the all sky in the J (1.25 µm), H (1.65 µm), and K s (2.17 µm) bands. Twotelescopes; one at Mt. Hopkins, Arizona, U.S.A. and another at Cerro Tololo, Chile, are exclusively devoted for this project to cover the northern and southern sky, respectively. The
identical NICMOS3 arrays are used for three bands at two telescopes. The J -, H -, andK s -band observations are conducted simultaneously with a 7.8 s exposure per frame. The
FOV is 8.50 ×8.50 with the pixel scale of 100 pixel−1 .
The Second Incremental Data Release of 2MASS, which was released in March 2000,
consists of two data sets; the Point Source Catalog (PSC) and the Extended Source Catalog(XSC). The release covers 19680.8 square degrees (∼47% of the all sky; Fig. 5.3). OMC-2
and OMC-3 are fully covered.

Figure 5.3: Sky coverage by the 2MASS Second Incremental Data Release. It covers ∼47% of the all sky(the shining parts of the map; http://www.ipac.caltech.edu/2mass). OMC-2 and OMC-3 are fully coveredat R.A. ∼ 5h 30m and decl. ∼ –5◦ .

The PSC contains the position and the magnitude of 157,820,597, 149,650,034, and130,337,158 sources in the J, H, and K s band, respectively. The astrometric accuracy is∼0.100 both in the R.A. and decl. directions with a negligible systematic offset from the
Astrographic Catalog/Tyco (ACT) catalog (Fig. 5.4). The photometric accuracy is given in
Figure 5.5, where the uncertainties in magnitudes are less than 0.1 mag for the J -, H -, andK s -band sources brighter than 15.8 mag, 15.1 mag, and 14.3 mag, respectively.
We consulted the PSC and found that ∼600 sources are in the FOV of Chandra. These5.1. X-RAY OBSERVATION WITH CHANDRA/ACIS

99

sources are correlated with QUIRC and Chandra sources, and were used to evaluate theirastrometric and photometric accuracy.

Figure 5.4: Distribution of the R.A. and decl. differences of ∼358,000 sources between 2MASS PSC and
ACT (bottom left) and its profiles on R.A. (top left) and decl. (bottom right) axes. The 1 σ values for bothprofiles (=the typical astrometric accuracy of 2MASS PSC) are ∼0.100 (http://www.ipac.caltech.edu/2mass).

2MASS Counterpart of Chandra Sources
We searched for the 2MASS counterpart of the Chandra sources in the following manner.
In the ACIS-I and ACIS-S FOVs, we found 638 2MASS sources. First, we searched for the
2MASS source closest to each Chandra source within a 300 radius. Second, we conversely
searched for the Chandra source closest to each 2MASS source within a 300 radius. Thus wepicked up the closest Chandra-2MASS pairs. The systematic position offset of the Chandra
sources from their 2MASS counterpart was found to be −0.1800 and 0.2100 in the direction

100

CHAPTER 5. CHANDRA AND QUIRC OBSERVATIONS

Figure 5.5: Photometric accuracy of sources detected in a calibration field. The uncertainty in magnitudes (vertical axis) versus the mean magnitude (horizontal axis) is plotted in black (sources detected atleast 16 out of the 18 trials) and in red (sources detected fewer than 16 times) separately for the J (top),
H (middle), and K s (bottom) band. The dotted bars indicate the r.m.s. averaged in each 0.5 mag bin(http://www.ipac.caltech.edu/2mass).

5.1. X-RAY OBSERVATION WITH CHANDRA/ACIS

101

of R.A. and decl., respectively. After correcting the Chandra positions for the systematic
offsets, we repeated the same procedure for the 2MASS counterpart search. Finally, we
found that 237 out of 398 (∼60%) Chandra sources have the 2MASS counterpart.

5.1.5

Results

Source List
The results of the X-ray imaging analysis are compiled in Table A.1 with the X-ray source
numbers, positions corrected for the systematic offset from the 2MASS frame, detector raw
counts, and HRs. The X-ray sources can be referred following the International Astronomical
Union (IAU) convention; e.g., CXOU J05343860−0508428 for the source No. 1.

Astrometric Accuracy
Figure 5.6 shows the differences between the Chandra and 2MASS positions both in the R.A.
and decl. directions. We found that ∆R.A. = 0.0000 ±0.4000 (1 σ) and ∆decl. = 0.0100 ±0.3600(1 σ), which indicates that the Chandra positions are determined with the accuracy of thesize of a Chandra pixel (0.49200 ) and the systematic offset between Chandra and 2MASS
positions is negligible.

Survey Depth
Figure 5.7 shows the histogram of X-ray counts. The peak of the histogram (101.5 = 32
counts) roughly corresponds to the completeness limit of this observation, while the minimum
number of counts (3 counts) gives the flux of the faintest detected sources. To convert the
X-ray counts into the X-ray flux or luminosity, we made an empirical relation between thesetwo parameters using the result of the spectral fitting of bright Chandra sources (Figs. 7.22
and 7.23). The completeness limit was estimated to be ∼10−14.5 ergs s−1 cm−2 in flux and∼1029.1 ergs s−1 in luminosity in the 0.5–8.0 keV range. The X-ray flux and the luminosity of
the faintest detected source were ∼10−15.5 ergs s−1 cm−2 and ∼1028.1 ergs s−1 , respectively.

102

CHAPTER 5. CHANDRA AND QUIRC OBSERVATIONS

Figure 5.6: Astrometric accuracy of Chandra sources. The difference of R.A. and decl. in the Chandra
and 2MASS positions (∆R.A. and ∆decl., respectively) is plotted for Chandra–2MASS counterpart pairs.
The solid square at the center represents the size of a Chandra pixel of 0.49200 ×0.49200 .

5.1. X-RAY OBSERVATION WITH CHANDRA/ACIS

Figure 5.7: Histogram of Chandra counts of all detected sources.

103

104

CHAPTER 5. CHANDRA AND QUIRC OBSERVATIONS

5.2

NIR Observation with UH88/QUIRC

5.2.1

Observation

In two points, the 2MASS data are not sufficient to find the NIR counterpart of our Xray sources and to identify their nature. One point is that the 2MASS data sometimes
lack J -, H -, or both band detections in star-forming regions, where the extinction by dense
ISM makes sources heavily reddened. Another point is that the 2MASS depth is not deep
enough to match the depth of our Chandra observation. Casanova et al. (1995)[29] derived
an empirical relation between the un-dereddened J -band magnitude (J ) and the X-ray flux
(FX ) in the 1.0–2.4 keV band using T Tauri star samples in the ρ Ophiuchi cloud (D =160 pc) detected by ROSAT, which is expressed aslog FX (4πD)2 ∼ −0.30J + 32.

(5.1)

The faintest detected sources of our Chandra observation have FX ∼ 10−15.5 ergs s−1 cm−2 in
0.5–8.0 keV at the distance of D = 450 pc, which can be converted to FX ∼ 2×10−16 ergs s−1 cm−2in the 1.0–2.4 keV band assuming a thin-thermal plasma spectrum of 1 keV temperature. If
the equation (5.1) can be applied to other YSOs, the required NIR detection limit would be
J ∼ 17 mag. In order to complement the 2MASS data with fainter sources than the 2MASS
limit, we conducted deeper NIR observations in OMC-2 and OMC-3 with the J -band integration time twice longer than that of the H and K bands.
We used QUIRC mounted on the Cassegrain focus of the University of Hawaii 88 inch
(2.2 m) telescope (UH88; Hodapp et al. 1997[89] ). QUIRC provides a 3.20 ×3.20 FOV withthe pixel scale of 0.18900 pixel−1 . The smaller pixel scale than that of the 2MASS detectors
is more appropriate to pick up sources contaminated by diffuse emissions, particularly in thesouthern half of our study field (Fig. 5.9).
We conducted a mosaic mapping observation to sweep the Chandra ACIS-I FOV (Fig. 5.8).
We first covered the uppermost row (frame Nos .1–5) of the mosaic by shifting the field centerby 1.60 (half of the side of the QUIRC FOV) from east to west. Then, we moved 1.60 southward and covered the second uppermost row (frame Nos. 6–13) by inversely shifting fromwest to east. We continued these raster scans to reach the lowermost row of the mosaic. In
this way, we can minimize dead times due to the shifts of field center and reduce the effect ofghost signals caused by residual electrons in detector pixels. In total, we swept the Chandra
FOV with 169 QUIRC FOVs that amount to ∼512 arcmin2 .

5.2. NIR OBSERVATION WITH UH88/QUIRC

105-4:55:00
13

decl. (J2000.0)-5:00:00

05:00

10:00

14

15

12

1

2

3

4

5

11

10

9

8

7

6

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169

20:00
5:36:00

40

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35:00

40

R.A. (J2000.0)
Figure 5.8: Configuration of our QUIRC mosaic mapping observations. The positions of 169 frame centers
are marked with crosses with the relevant frame number. The frames are tiled at the intervals of 1.60 tosweep the Chandra ACIS-I FOV (solid oblique square). Each frame covers a 3.20 ×3.20 square region (the size
is shown at the right bottom) centered on each cross. When the all frames are combined, any point in the
thick lines (∼512 arcmin2 ) is covered at least by one frame, while that in the gray region (∼360 arcmin2 )is covered by four frames. The contours show the 1.3 mm intensity (Chini et al. 1997[35] ). OMC-2 andOMC-3 are separated by the dashed line into the southern and northern part of the integral-shaped ridge,
respectively.

106

CHAPTER 5. CHANDRA AND QUIRC OBSERVATIONSEach 169 frame was exposed for 60 s. We conducted the mosaic mapping once in the H
and K band and twice in the J band, spending six half-nights of February 4–6 and March
11–13, 2001 (Table 5.1). All nights were photometric with the seeing of 0.700 –1.100 . In one
sweep, any region inside the Chandra field except for edges (the gray region in Fig. 5.8) wascovered four times, which makes the nominal exposure time to be 240 s in the H and K
band and 480 s in the J band.
Table 5.1: QUIRC observation log

dateband frame numbersa
2001 Feb. 04
K
Nos. 1–169
2001 Feb. 05
J
Nos. 1–52
2001 Feb. 06
H
Nos. 1–169
2001 Mar. 11
J
Nos. 1, 51–169
2001 Mar. 12
J
Nos. 1–129
2001 Mar. 13
J
Nos. 1, 107–169
a

The frame numbers (see Fig. 5.8) covered in each night. In the J -band sweep, for which we spent fournights, some frames are duplicated; i.e., the frame No. 1 at the beginning of every run to check the telescope
positioning accuracy, and frame Nos. 51–52 and 107–129 to check any difference of image quality in different
nights. All these duplicated frames were confirmed to have similar quality and were combined equally into
the final J -band image with the correction for the exposure time.

5.2.2

Data Reduction

All QUIRC frames were reduced following the standard procedures using IRAF7 ; i.e., dark
subtraction, flat fielding, sky subtraction, and bad pixel removal. Dark frames with a 60 s
integration time were taken at the end of each night for each filter, and were used to subtract dark current signals of source images. Flat frames were also taken at each night foreach filter by observing the telescope dome, and were used to correct for the pixel-to-pixel
variation in quantum efficiency. Sky frames were constructed for each frame set of a mosaic
image by adopting the median of 169 ADU values at a given pixel. SExtractor (Bertin &Arnouts 1996[21] ) was used for source extraction and photometry.
For the purpose of the astrometric and photometric calibration of all frames, we consulted the 2MASS catalog. We tentatively extracted sources from each frame and correlated
7

See http://iraf.noao.edu/.

5.2. NIR OBSERVATION WITH UH88/QUIRC

107

them with the 2MASS sources using WCSTools8 . We found that all QUIRC frames have
18–145 sources including 4–51 sources with the 2MASS counterpart. Using the QUIRC–
2MASS counterpart pairs, we first shifted each QUIRC frame so that the mean separation
between QUIRC sources and their 2MASS counterpart in the frame reaches the minimum.
Second, we multiplied each QUIRC frame with a constant value that was derived by theleast-square method in order to match the QUIRC photometry with the 2MASS photometryof QUIRC–2MASS counterpart pairs. In this way, we used the 2MASS sources as standard
stars. Sources brighter than 11 mag or fainter than 16 mag were not used for this procedure
because of the unguaranteed linearity of QUIRC or because of the large uncertainty in the
2MASS photometry.
All the frames, which were thus corrected for astrometry and photometry, were combined
into three large mosaic images of the J, H, and K bands. The pseudo-color image is shown in
Figure 5.9. Some discontinuities are left in the image because of the difficulty in determining
the background intensity level, particularly in regions contaminated by diffuse emissions.

5.2.3

Source Extraction and Photometry

Prior to source detection, all the mosaic images were binned with neighboring 2×2 pixels andsmoothed with a Gaussian function to attain better signal-to-noise ratio. For the K -band
mosaic image thus improved, we extracted NIR sources above 3 σ level. In SExtractor, we
can choose any convolution masks φ(x, y) in peak finding procedures to increase detectabilityof faint sources. The two dimensional Gaussian mask φG (x, y) is routinely used, where
Ã

!

1
1
1
φG (x, y) =exp − 2 − 2 .
2πσx σy2σx 2σy(5.2)

However, we adopted the Mexican hat function φM H (x, y) for the mask; i.e.,
"Ã

!

Ã

!#

∂
∂
+1 + y+ 1 φG (x, y)
φM H (x, y) =
x
∂x
∂y
Ã
!
Ã
!
1
x2
y2
x2
y2
=
2 − 2 − 2 exp −−.
2πσx σyσx σy2σx 2σy(5.3)

This function has a positive kernel surrounded by a negative annulus. The limited spatial
extent of the kernel favors sources with intrinsically or instrumentally broadened size of
8

See http://tdc-www.harvard.edu/software/wcstools/ for more details.

108

CHAPTER 5. CHANDRA AND QUIRC OBSERVATIONS-4:55:00

decl. (J2000.0)-5:00:00

05:00

10:00

15:00

20:00

5:36:00

40

20
35:00
R.A. (J2000.0)

40

Figure 5.9: Three-color image of QUIRC observations. The neighboring 8×8 pixels are binned. Red, green,
and blue are for the K -, H -, and J -band intensity, respectively.

5.2. NIR OBSERVATION WITH UH88/QUIRC

109

about (σx , σy ) to be detected. We confirmed that a Mexican hat function of the seeing size
radius gives the most robust result among several masks with various radii we examined,
particularly in regions contaminated with diffuse emissions. With careful visual inspections
on the output, we removed (1) sources at the edge of the mosaic images, (2) ghosts ofbright sources, and (3) spurious detections (in most cases, diffuse structures were identified
as point-like sources). As a result, we picked up 1448 K -band sources.
For each K -band detected source, we derived the J -, H -, and K -band magnitude withthe adaptive aperture photometry. For source with less than a 3 σ detection in the J, H, orboth bands, we calculated the 3 σ upper limit of their magnitudes.

5.2.4

2MASS Counterpart of QUIRC Sources

We correlated all the QUIRC sources with the 2MASS catalog with the imtmc command in
the WCSTools package and found that 692 (∼48%) have the 2MASS counterpart.

5.2.5

Results

Source List
Table B.1 lists the QUIRC sources with their source number, position, J -, H -, and K -band
magnitudes, and their 2MASS counterpart. Hereafter, we refer these sources following the
IAU convention; e.g., TKK J05342894−0508387 for the source No. 1. Note that all themagnitudes in the list are in the 2MASS color system. For sources that lack the J, H, orboth band detections, we listed the 3 σ upper limit of the flux (lower limit of the magnitude)
and labeled them with “>”. For QUIRC magnitudes brighter than 11 mag, we replaced themwith the 2MASS magnitudes with the label “†” if they have the 2MASS counterpart. If they
do not have the 2MASS counterpart, we labeled the magnitudes with “<” and recognizedthem as the lower limit of the flux (the upper limit of the magnitude).

Astrometric and Photometric Accuracy
Using the QUIRC–2MASS counterpart pairs, we evaluated the accuracy of the QUIRC astrometry and photometry in the following way.

110

CHAPTER 5. CHANDRA AND QUIRC OBSERVATIONSIn Figure 5.10, we plotted differences between the QUIRC and 2MASS positions bothin the R.A. and decl. directions. We found that ∆R.A. = 0.04800 ±0.16100 (1 σ) and ∆decl.
= 0.02200 ±0.14800 (1 σ), which indicates that the QUIRC positions are determined with theaccuracy of the size of a QUIRC pixel (0.18900 ) and the systematic offset between QUIRC
and 2MASS positions is negligible.

Figure 5.10: Astrometric accuracy of QUIRC sources. The difference of R.A. and decl. in the QUIRC
and 2MASS positions (∆R.A. and ∆decl., respectively) are plotted for each QUIRC–2MASS pair. The solid
square at the center represents a QUIRC pixel size of 0.18900 ×0.18900 .

In Figure 5.11, we plotted the QUIRC and 2MASS magnitudes of QUIRC–2MASS
counterpart pairs separately for each band. The linear relations (2MASS magnitudes equal
QUIRC magnitudes) are violated at the brighter side than ∼11 mag due to the unguaranteedlinearity of QUIRC, where its saturation limit of 44000 ADU counts corresponds to ∼11 magin our observations. For sources fainter than 11 mag in the QUIRC and 2MASS magnitudes,
we calculated the difference between these magnitudes for each band (∆mJ , ∆mH , and5.2. NIR OBSERVATION WITH UH88/QUIRC

111∆mK ). We found that ∆mJ = −0.06 ± 0.22 mag (1 σ), ∆mH = −0.07 ± 0.19 mag (1 σ),and ∆mK = −0.04 ± 0.18 mag (1 σ), indicating that the QUIRC photometry fainter than
11 mag is consistent with the 2MASS photometry within ∼0.2 mag.
18

18

16

16

14

14

12

12

10

10

8

8

6

6
6

8

10

12

14

16

18

6

8

10

12

14

16

18

6

8

10

12

14

16

18

18
16
14
12
10
8
6
2MASS magnitude (mag)Figure 5.11: Photometric accuracy of QUIRC sources. The 2MASS and QUIRC magnitudes of the counterpart pairs are plotted separately for the (a) J, (b) H, and (c) K bands. Solid lines represent that the
2MASS magnitudes equal to the QUIRC magnitudes).

Survey Depth
We estimated the survey depth of our QUIRC observations in the following manner. First,
we embedded 500 artificial sources with 13.0–13.5 mag in the J -, H -, and K -band mosaic
images. The same source detection algorithm was employed to detect these artificial sources,
then the detection rate of sources with 13.0–13.5 mag was derived. The same procedure wasrepeated for sources of different magnitudes from 13.0 to 20.0 mag with 0.5 mag bins. The

112

CHAPTER 5. CHANDRA AND QUIRC OBSERVATIONS

detection rate at each magnitude bin is given in Figure 5.12 for the K (solid ), H (longdashed ), and J (short-dashed ) band, respectively. The 90% completeness limit (3 σ) was
thus estimated to be K ∼ 16.0 mag, H ∼ 16.5 mag, and J ∼ 17.5 mag.

Figure 5.12: Completeness limit of QUIRC observations. The fractions of detected artificial sources areshown with the solid (K ), long-dashed (H ), and short-dashed (J ) lines. The 90% (dotted line) completenesslimit is K ∼ 16.0 mag, H ∼ 16.5 mag, and J ∼ 17.5 mag.

In order to compare the depth of our observation with that of 2MASS, we made a histogram of the number counts of the K -band detected sources at each magnitude (Fig. 5.13).
The short- and long-dashed histograms respectively represent the number of the QUIRC
sources with and without the 2MASS counterpart, while the total is given in the solid histogram. The 2MASS catalog fails to detect some bright sources even in K < 14 mag, which ismainly due to the contamination by diffuse emission or to their binarity. This was confirmedby plotting the 2MASS source list on the 2MASS image.

5.2. NIR OBSERVATION WITH UH88/QUIRC

113

Figure 5.13: Source counts (d log N/dM ) of QUIRC K -band detected sources, where M is the magnitude
and N is the number of sources fainter than M mag. The solid histogram is the counts of all the QUIRC
K -band sources, while the short- and long-dashed histograms are those with and without the 2MASS counterpart, respectively.

114

5.2.6

CHAPTER 5. CHANDRA AND QUIRC OBSERVATIONSQUIRC Counterpart of Chandra Sources

Among 237 Chandra sources with the 2MASS counterpart, 30 sources lack either 2MASS
J -, H -, or K s -band detections. Together with 161 Chandra sources that have no 2MASS
counterpart, we hereafter call them the “2MASS-unIDed” Chandra sources. There are 183
and 9 2MASS-unIDed sources in the ACIS-I and ACIS-S2 FOVs. Using the QUIRC source
list (Table B.1), we searched for the NIR counterpart of 183 2MASS-unIDed ACIS-I sources
with a more elaborated procedure as follows.

Figure 5.14: Closest QUIRC–Chandra pairs with their separation and the X-ray off-axis angle on thevertical and the horizontal axis, respectively. The dotted curve is the 90% encircled energy radius (r90 ) of
1.49 keV X-rays at a given off-axis angle. Filled squares, which are below the dotted curve, are recognized
as the counterpart pairs. Open squares, which are above the dotted curve, are recognized as non-associatedpairs.

The Chandra PSF radii differ by more than an order of magnitude between on-axis
sources and those at the field edge, which deteriorates the position accuracy of sources

5.2. NIR OBSERVATION WITH UH88/QUIRC

115

at large off-axis angles. Therefore, in identifying the QUIRC counterpart of the Chandra
sources, we took the off-axis angle into account. First, we searched for the QUIRC source
closest to each Chandra source. Second, we conversely searched for the Chandra source
closest to each QUIRC source. Then, we picked up 159 QUIRC–Chandra pairs that are theclosest to each other. These pairs include those of physically associated (“counterpart pairs”)
and those of no physical association (“non-associated pairs”). In Figure 5.14, we plotted theseparation between the closest QUIRC–Chandra pairs as a function of the off-axis angle of
the Chandra source. We showed two groups by the filled and open squares, which are well
separated by the dotted curve indicating the 90% encircled energy radius (r90 ; ∼ 0.9 times
FWHM of a Gaussian PSF) of 1.49 keV X-rays as a function of the off-axis angle9 . Since r90
is the radius in which the 90% of incident X-ray photons are accumulated, it also represents
the position accuracy of the Chandra sources at each off-axis angle. We therefore regard theclosest QUIRC–Chandra pairs with the separation angle less than r90 (filled squares) to be
counterpart pairs, while those with larger separation angle of more than r90 (open squares) as
non-associated pairs. As a result, 75 2MASS-unIDed Chandra sources were newly found tohave the QUIRC counterpart (hereafter we call them “QUIRC-IDed” sources). The 2MASS
and QUIRC counterpart of Chandra sources and their NIR colors are given in Table A.1.
Note that the NIR colors are converted to the CIT color system (Sect. 6.2).

A (203)A (203)

B (29)C (153)

D (75)

E (107)

Figure 5.15: NIR identifications of Chandra ACIS-I sources. (top) 2MASS identifications. Those with the
2MASS J -, H -, and K s -band detections (“2MASS-IDed”) are in A, those lack at least one detection in thesethree bands are in B, and those with no 2MASS counterpart are in C. B and C are called “2MASS-unIDed”
sources, for which the QUIRC counterpart is searched. (bottom) QUIRC identifications. Those with the
QUIRC counterpart (“QUIRC-IDed”) are in D, while those without 2MASS nor QUIRC counterpart (“NIRunIDed”) are in E. 2MASS-IDed and QUIRC-IDed sources (A and D) are collectively called “NIR-IDed”
sources. The number of sources are shown in parentheses.

9

See http://asc.harvard.edu/udocs/docs/POG/MPOG/index.html.

116

CHAPTER 5. CHANDRA AND QUIRC OBSERVATIONSChapter 6
NIR-IDed X-ray Sources: (1) NIR
Properties
Contents
6.1

6.2

NIR Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
6.1.1

K -band Luminosity Function . . . . . . . . . . . . . . . . . . . . . 118

6.1.2

Color-color Diagram of QUIRC Sources . . . . . . . . . . . . . . . 119

6.1.3

Color-magnitude Diagram of QUIRC Sources . . . . . . . . . . . . 120

The NIR-IDed X-ray Sources . . . . . . . . . . . . . . . . . . . . 124
6.2.1

Cloud Membership . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

6.2.2

Evolutional Class Estimates . . . . . . . . . . . . . . . . . . . . . . 124

6.2.3

Mass and Bolometric Luminosity Estimates . . . . . . . . . . . . . 127

117

118

CHAPTER 6. NIR-IDED X-RAY SOURCES: (1) NIR PROPERTIESIn this chapter, the NIR properties of the QUIRC sources and NIR-IDed X-ray sources
are discussed. Using color-color and color-magnitude diagrams of the J, H, and K bands, ample information on physical parameters of YSOs can be obtained such as the evolutional class,disk existence, stellar mass, bolometric luminosity and amount of extinction. In Sect. 6.1,
we examine the NIR colors of all QUIRC sources and describe the overall features of OMC-2
and OMC-3. In Sect. 6.2, we zoom in to the NIR-IDed X-ray sources (=NIR sources with
the X-ray counterpart), and estimate their mass and evolutional class to classify them into
several groups.

6.1

NIR Sources

6.1.1

K -band Luminosity Function

We made a histogram of the K -band-detected QUIRC sources at each K -band magnitude(K -band luminosity function; KLF) in Figure 6.1. The short- and long-dashed histograms
respectively represent the KLF of QUIRC sources with and without the 2MASS counterpart,while the total is given in the solid histogram. The dashed-and-dotted histogram is the KLF
of NIR-IDed X-ray sources normalized to the area of QUIRC FOV. In the KLF, we canestimate the back- and foreground source contamination. The dotted curve shows the backand foreground source counts predicted by a Galactic star count model (the SKY model;
Cohen 1993[38] ; Cohen 1994[39] ; Cohen, Sasseen, & Bowyer 1994[40] ; Cohen 1995[41] ) assuming
no interstellar extinction. There is an overall extinction of AK ∼ 1 mag in this region(Fig. 6.4; see the relevant discussion in the text), which shifts the dotted curve rightward by∼1 mag to the dashed curve. The contamination is not negligible for sources fainter thanK ∼ 15 mag. For brighter sources, however, we can assume that most of them are cloud
members.
The peak of KLF for all the QUIRC sources (solid histogram) at 12–13 mag is a realfeature when the completeness limit (K ∼ 16 mag) and back- and foreground contamination
are taken into consideration. This has been inferred by Jones et al. (1994)[101] , who studied
the KLF of OMC-2 sources. The peak of KLF is often seen in the young associations like theOrion Nebula Cluster (Ali & DePoy 1995[2] ; Hillenbrand & Carpenter 2000[86] ) and can be
explained in terms of difference in the mass-to-luminosity relation between main sequenceand pre-main-sequence sources (Muench, Lada, & Lada 2000[137] ). The peak magnitude is6.1. NIR SOURCES

119

consistent with the cloud age of ∼1 Myr (Ali & DePoy 1995[2] ), which was also confirmed
by other methods (Sect. 3.1).

Figure 6.1: QUIRC K -band-detected source counts at each magnitude in the 2MASS color system. The
solid histogram is the counts of all the QUIRC K -band sources, while the short- and long-dashed histograms are those with and without the 2MASS counterpart, respectively. The dashed-and-dotted histogram is the KLF of the NIR-IDed X-ray sources normalized to the area of QUIRC FOV. The uncertainty√
of counts bin−1 is given for the solid histogram. The dotted curve shows the back- and foreground source
counts predicted by a Galactic star count model assuming no extinction. When a uniform extinction of
1 mag is assumed, this curve should be shifted rightward by 1 mag to the dashed curve.

6.1.2

Color-color Diagram of QUIRC Sources

We first converted the J -, H -, and K -band magnitudes in the 2MASS color system in Table
B.1 (J 2MASS , H 2MASS , and K 2MASS ) to the CIT color system (J CIT , H CIT , and K CIT ) using
the following conversion formula (Carpenter 2001[27] ):JCIT = 0.947J2MASS + 0.053K2MASS + 0.036

(6.1)

120

CHAPTER 6. NIR-IDED X-RAY SOURCES: (1) NIR PROPERTIES(J − H)CIT = 0.929(J − H)2MASS + 0.040(6.2)(H − K)CIT = 0.975(H − K)2MASS − 0.027(6.3)

The color-color diagram (Lada & Adams 1992[114] ) was made using all QUIRC sources
with significant J -, H -. and K -band detections (1305 out of 1448 sources). Figure 6.2 showsthe (J –H )/(H –K ) diagram, where QUIRC sources with and without the 2MASS counterpart
are respectively shown with open and filled symbols. The intrinsic colors of giants and dwarfs
are given by the thick solid curves (Tokunaga 2000[185] ). The emission from the circumstellar
disks of cTTSs gives NIR excess on the giant and dwarf colors, hence cTTSs are aligned
from bottom left to top right along the cTTS locus in the thick solid line (Meyer, Calvet,& Hillenbrand 1997[130] ). These colors change their position along the reddening vector as
increasing interstellar and circumstellar medium. Therefore, sources between the right andmiddle reddening lines are reddened cTTSs (diamonds), while those between the middle andleft reddening lines are reddened wTTSs and some fraction of cTTSs (triangles). Sources
located to the right of the right reddening line are surrounded by extended envelopes in
addition to the disks, hence they are reddened more than disks alone (Strom, Kepner, &Strom 1995[177] ). These sources (hexagons) are classified to be class I protostars.
Cares should be taken that back- and foreground sources are included in our NIR source
samples. However, sources with NIR excess (protostars and cTTSs; hexagons and diamonds
in Fig. 6.2) can be safely assumed to be YSOs, namely cloud members.

6.1.3

Color-magnitude Diagram of QUIRC Sources

In order to estimate the stellar mass and extinction of NIR sources, we employed the J /(J –H )color-magnitude diagram (Fig. 6.3), where QUIRC sources with significant J - and H -band
detections are shown in squares. Among them, filled squares are those with NIR excess.
All sources are assumed to be at the distance of 450 pc. The intrinsic colors of sourcesat the age of 1 Myr are shown in the solid curves for the mass range of 0.002–1.4 M¯(Baraffe et al. 1998[16] ) and 1.4–7.0 M¯ (Siess, Dufour, & Forestini 2000[171] ). As a result of
the extinction, these intrinsic colors are reddened in the direction of the reddening vector at
the top right of Figure 6.3. By moving the position of squares backward along the reddening
vector to the 1 Myr isochrone curves, the mass and amount of extinction (AV ) can be
estimated for each source.

6.1. NIR SOURCES

121

Figure 6.2: Color-color diagram of QUIRC sources with significant J -, H - and K -band detections. Openand filled symbols are QUIRC sources with and without 2MASS counterpart, respectively. Hexagons anddiamonds are classified as protostars and cTTSs, while triangles are the mixture of main sequence, wTTSs,
and cTTSs. Squares are in none of these classifications. The intrinsic colors of dwarfs and giants are
given with thick solid curves, while the cTTS locus is with the thick solid line. The arrow at the bottom right gives the reddening vector of AV =10 mag. The slope of the reddening lines is assumed to be
E(J–H)reddening /E(H–K)reddening = 1.69 (Meyer et al. 1997[130] ). The typical uncertainty of colors is roughly±0.1 mag.

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CHAPTER 6. NIR-IDED X-RAY SOURCES: (1) NIR PROPERTIES

Figure 6.3: Color-magnitude diagram of QUIRC sources with significant J - and H -band detections(squares). Among them, filled are those with NIR excess. The 1 Myr isochrone curves (thick solid
curves) are from Baraffe et al. (1998)[16] for 0.002 M¯ ≤ M ≤ 1.4 M¯ and Siess et al. (2000)[171] for
1.4 M¯ ≤ M ≤ 7.0 M¯ . Two dashed lines show the detection limit of J = 17.5 mag and H = 16.5 mag.
The arrow at the top right indicates the reddening vector of AV =10 mag. Reddening lines for 2.0 M¯ ,0.2 M¯ , and 0.08 M¯ are given with solid lines. The typical uncertainty of colors and magnitudes is roughly±0.1 mag.

6.1. NIR SOURCES

123

To examine the distribution of NIR extinction, we made the histogram of the K -band
extinction (AK ) in Figure 6.4. The AK value of each source was converted from AV using
AK /AV = 0.125 (Mathis 2000[123] ). Sources in the mass range of 0.2 M¯ ≤ M ≤ 2.0 M¯and J > 17.5 mag (Fig. 6.3) are used to construct the histogram. The observational bias
in favor of low extinction sources is thus avoided for AV < 20 mag (AK < 2.5 mag). The
typical AK was estimated to be ∼1 mag.

Figure 6.4: Histogram of the K -band extinction (AK ) derived from NIR sources in the mass range of
0.2 M¯ < M < 2.0 M¯ and J > 17.5 mag. The AV value of each source was estimated from Figure 6.3, andconverted to AK using AK /AV = 0.125 (Mathis 2000[123] ). The histogram was fitted with an exponentialfunction in the positive AK region to derive the typical value of AK ∼ 1 mag.

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CHAPTER 6. NIR-IDED X-RAY SOURCES: (1) NIR PROPERTIES

6.2

The NIR-IDed X-ray Sources

6.2.1

Cloud Membership

Krishnamurthi et al. (2001)[108] observed the core of the Pleiades star cluster with Chandra
for 36 ks and found that a significant fraction of X-ray sources are likely to be AGNs. We
examined the contamination of our X-ray samples by AGNs and concluded that there is only
a negligible number of AGNs among NIR-IDed X-ray sources for the following reason.
The number count of galaxies (N ) per square degree per magnitude at a certain K -band
magnitude (K) is given bydN= 4000 × 10α(K−17) ,(6.4)
dK
where α = 0.67 for 10 mag < K < 17 mag (Tokunaga 2000[185] ). The number of galaxies in
the range of Kmin mag < K < Kmax mag is then estimated by
Z Kmax
Kmin

4000
dN
dK =
{10α(Kmax −17) − 10α(Kmin −17) }.
dK
α log 10

(6.5)

The NIR counterparts of the Chandra sources have a K -band magnitude in 6 mag < K <15 mag. We substituted Kmin = 6 and Kmax = 15 for simplicity, though the equation (6.5)
is valid only for Kmin > 10 mag. Still, this gives us a good estimate since the second termof the right-hand side is negligible compared to the first term in this case. Considering the
Chandra FOV, the estimated number of galaxies in the range of 6 mag < K < 15 mag is∼12. This is only ∼0.8% of all the NIR sources in the same magnitude range. Moreover,the background galaxies in this direction suffer a significant extinction due to dense ISM,
which makes the contribution of extragalactic sources to our NIR samples even smaller. This
excludes the possibility of NIR-IDed X-ray sources to be extragalactic AGNs.
The KLF of NIR-IDed X-ray sources (Fig. 6.1) indicates that most of the X-ray sources
have the K -band magnitude of K < 14 mag, where the contamination by back- and foreground galactic sources is negligible. We hereafter regard all the NIR-IDed X-ray sources as
cloud members.

6.2.2

Evolutional Class Estimates

Table A.1 lists the J -band magnitude and (J –H ) and (H –K ) colors of NIR-IDed Chandra
sources in the CIT color system. Using these colors, we first made the (J –H )/(H –K )

6.2. THE NIR-IDED X-RAY SOURCES

125

color-color diagram (Fig. 6.5), where NIR-IDed Chandra sources are plotted. Filled andopen symbols are QUIRC-IDed and 2MASS-IDed Chandra sources. The arrows on symbols
indicate the lower limit of colors; i.e., the upward arrows are due to the lack of the J -band
detections and the rightward arrows are due to the saturation in the K band. Following theclassification scheme addressed in the previous section, we picked up protostars, cTTSs, andwTTSs (hexagons, diamonds, and triangles). Some sources can not be classified in any ofthese classes either because they are out of the three regions (squares) or they have no J -,H -, or both band detections.
We have to keep in mind that the K -band magnitude is not always sensitive enoughto detect excess emissions from circumstellar disks. Recent Infrared Space Observatory observations on R Coronae Australis, Chamaeleon, and ρ Ophiuchi dark clouds indicate thatthe classification based only on the J, H, and K -band data underestimates the number of
YSOs with disks (Olofsson et al. 1999[144] ; Persi et al. 2000[152] ; Bontemps et al. 2001[24] ).
Haisch et al. (2001)[76] combined the MIR with NIR photometry on NGC 2024 and reported
that about one-third of class II sources are recognized not to have excess emissions with the(J –H )/(H –K ) diagram alone, hence are classified as class III sources.
In classifying the NIR-IDed X-ray sources, therefore, we additionally used Hα emission(Herbig & Bell 1988[83] ) and U V excess (Rebull et al. 2000[160] ) data to complement the
NIR excess data. The Hα emission line is directly related to disks and its equivalent widthis used to discriminate cTTSs (>10 Å) and wTTSs (<10 Å). The NIR and UV excess
data work complementarily. The former is sensitive to disks of earlier-type sources withhigher photospheric temperature, while the latter is sensitive to later-type sources withlower temperature, because of the contrast between the photosphere and disk colors. The
UV excess of cTTSs is considered to originate from the boundary layer of an accretion disk
(Hartigan et al. 1991[79] ), making it another indicator of disk existence.
Among sources classified as wTTSs in the (J –H )/(H –K ) color-color diagram, four (I13,
I248, I324, and I334) and eleven (I111, I122, I150, I200, I237, I308, I319, I322, I328, I332,
and S4) sources are reclassified into cTTSs based respectively on their Hα and U V excess
emissions. Consequently, we identified 13 protostars, 59 cTTSs, and 170 wTTSs among 278
NIR-IDed X-ray sources. The result of the classification is summarized in Table A.1.
We examined the position of Chandra sources separately for each class (Fig. 6.6). Protostars are clearly concentrated along the 1.3 mm ridge. Since cores seen in the millimeter
continuum are the sites of on-going star formation, this reinforces the idea that they are

126

CHAPTER 6. NIR-IDED X-RAY SOURCES: (1) NIR PROPERTIES

Figure 6.5: Color-color diagram of NIR-IDed X-ray sources. The 2MASS-IDed and QUIRC-IDed Chandra
sources are plotted with open and filled symbols, respectively. Hexagons, diamonds, and triangles areclassified to be protostars, cTTSs, and wTTSs, while squares are in none of these classes. The intrinsic
colors of dwarfs and giants are given with solid curves, while the cTTS locus is with solid line. The arrowat the bottom right gives the reddening vector of AV =10 mag. The slope of the reddening lines is assumed
to be E(J–H)reddening /E(H–K)reddening = 1.69 (Meyer et al. 1997[130] ). The typical uncertainty is roughly±0.1 mag.

6.2. THE NIR-IDED X-RAY SOURCES

127

YSOs at the very early stage. Most of protostars also accompany apparent NIR nebulosity
in the K -band image, which indicates that they are deeply embedded sources. The spatial
distribution of cTTSs is also correlated with the ridge, although wTTSs and X-ray sources
with no NIR counterpart (Fig. 6.8) are not.

6.2.3

Mass and Bolometric Luminosity Estimates

We next made the J /(J –H ) color-magnitude diagram (Fig. 6.7), where NIR-IDed Chandra
sources are shown in squares. Among them, filled squares are those with NIR excess. Squares
with the rightward arrows indicate the saturation in the H band, and those with both therightward and the downward arrows have H - but not J -band detection.
We categorized the NIR-IDed X-ray sources into four groups based on their mass. Using this diagram, we can estimate the mass with the J -band magnitude because nearly
all the emission in this band is photospheric for late-type pre-main-sequence stars (Strom& Strom 1994[176] ). Magnitudes in the longer wavelengths are affected by NIR excess
emissions from circumstellar dust, while those in the shorter wavelengths are by UV excess emissions from the disk-boundary layer, giving a significant overestimate of the mass
(Gagné et al. 1995[61] ).
Using the theoretical calculations of isochrone curves by Baraffe et al. (1998)[16] forsources in 0.002 M¯ ≤ M ≤ 1.4 M¯ and Siess et al. (2000)[171] in 1.4 M¯ ≤ M ≤ 7.0 M¯ ,we estimated the mass (Table A.1), which is quantized depending on the grid of thesecomputations. The bolometric luminosity is also derived for each source in the same way.
Among 278 NIR-IDed X-ray sources, 268 have significant J - and H -band detections.
These sources are separated into high mass (HM) with M > 10 M¯ , intermediate mass (IM)with 10 M¯ > M > 2.0 M¯ , low mass (LM) with 2.0 M¯ > M > 0.2 M¯ , and very low
mass (VLM) sources with M < 0.2 M¯ . For sources with M > 4.0 M¯ , where the J -band
magnitude is insensitive to the mass, we assumed that they have M = 4.0 M¯ except for I242,
which we classified into HM based on its spectroscopy observations (Kukarkin et al. 1971[111] ).
As a consequence, we found 1 HM, 21 IM, 139 LM, and 107 VLM sources. The spatial
distributions of these sources are given separately for each mass range in Figure 6.8.

-4:50:00-4:50:00

55:00

55:00

-5:00:00-5:00:00
decl. (J2000.0)

CHAPTER 6. NIR-IDED X-RAY SOURCES: (1) NIR PROPERTIES

decl. (J2000.0)

128

05:00

10:00

15:00

05:00

10:00

15:00

30

5:36:00

35:30
R.A. (J2000.0)

5:35:00

30

35:30
R.A. (J2000.0)

5:35:00-4:50:00-4:50:00

55:00

55:00

-5:00:00-5:00:00
decl. (J2000.0)(b) class II

decl. (J2000.0)(a) class I

5:36:00

05:00

10:00

15:00

05:00

10:00

15:00

30

5:36:00

35:30
R.A. (J2000.0)(c) class III

5:35:0030

5:36:00

35:30
R.A. (J2000.0)

5:35:00(d) others

Figure 6.6: Spatial distribution of Chandra sources (pluses) separately for (a) class I (protostars),(b) class II (cTTSs), (c) class III (wTTSs), and (d ) NIR-IDed sources that are classified into none ofthese three classes. The FOVs of ACIS and QUIRC are shown with solid lines. The contours in each panel
are the 1.3 mm intensity (Chini et al. 1997[35] ).

6.2. THE NIR-IDED X-RAY SOURCES

129

Figure 6.7: Color-magnitude diagram of NIR-IDed Chandra sources (squares). Among them, filled ones
are those with NIR excess. The 1 Myr isochrone curves (thick solid curves) are from Baraffe et al. (1998)[16]for 0.002 M¯ ≤ M ≤ 1.4 M¯ and from Siess et al. (2000)[171] for 1.4 M¯ ≤ M ≤ 7.0 M¯ . Two dashedlines show the detection limit of J = 17.5 mag and H = 16.5 mag. The arrow at the top right indicates thereddening vector of AV =10 mag. The reddening lines for 2.0 M¯ , 0.2 M¯ , and 0.08 M¯ are given withsolid lines. The typical uncertainty is roughly ±0.1 mag.

-4:50:00-4:50:00

55:00

55:00

-5:00:00-5:00:00
decl. (J2000.0)

CHAPTER 6. NIR-IDED X-RAY SOURCES: (1) NIR PROPERTIES

decl. (J2000.0)

130

05:00

10:00

15:00

05:00

10:00

15:00

30

5:36:00
35:30
R.A. (J2000.0)

5:35:0030-4:50:00-4:50:00

55:00

55:00

-5:00:00-5:00:00
decl. (J2000.0)

05:00

10:00

15:00

5:35:00(b) LM (2.0 M¯ > M ≥ 0.2 M¯ )decl. (J2000.0)(a) HM, IM (M ≥ 2.0 M¯ )5:36:00
35:30
R.A. (J2000.0)

05:00

10:00

15:00

30

5:36:00
35:30
R.A. (J2000.0)

5:35:00(c) VLM (M < 0.2 M¯ )30

5:36:00
35:30
R.A. (J2000.0)

5:35:00(d) NIR-unIDed

Figure 6.8: Spatial distribution of Chandra sources (pluses) separately for (a) HM and IM (M ≥ 2.0 M¯ )(b) LM (2.0 M¯ > M ≥ 0.2 M¯ ), (c) VLM (M < 0.2 M¯ ), and (d ) NIR-unIDed X-ray sources. The
FOVs of ACIS and QUIRC are shown with solid lines. The contours in each panel are the 1.3 mm intensity(Chini et al. 1997[35] ).

Chapter 7
NIR-IDed X-ray Sources: (2) X-ray
Properties
Contents
7.1

Temporal Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

7.2

Spectral Analysis

7.3. . . . . . . . . . . . . . . . . . . . . . . . . . . 139

7.2.1

Spectrum Models and Fittings . . . . . . . . . . . . . . . . . . . . 139

7.2.2

One-temperature Plasma Fittings . . . . . . . . . . . . . . . . . . . 140

7.2.3

Two-temperature Plasma Fittings . . . . . . . . . . . . . . . . . . 151

7.2.4

Time-sliced Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . 159

Relations between Parameters. . . . . . . . . . . . . . . . . . . 162

7.3.1

X-ray absorption versus NIR extinction . . . . . . . . . . . . . . . 162

7.3.2

X-ray counts versus X-ray flux . . . . . . . . . . . . . . . . . . . . 162

7.3.3

X-ray counts versus X-ray luminosity

131. . . . . . . . . . . . . . . . 162

132

CHAPTER 7. NIR-IDED X-RAY SOURCES: (2) X-RAY PROPERTIESIn this chapter, we discuss the X-ray properties of NIR-IDed Chandra sources. In order
to concentrate on sources with enough statistics, we deal with bright ACIS-I sources inthis and the following chapters. In Sect. 7.1, we conduct temporal analysis and illustratethat about half of them show flux variability including flares. In Sect. 7.2, we perform
spectral analysis. By fitting with one-temperature thin-thermal plasma model, we derive
the plasma temperature (kB T ), X-ray luminosity (LX ), and the amount of absorption (NH ).
When rejected, we apply two-temperature plasma model to fit the spectra. About 90% of
sources are fit with either by one-temperature or two-temperature plasma model. Finally, inSect. 7.3, we examine the relations among these parameters.

7.1

Temporal Analysis

One of the most notable characteristics of the X-ray emissions from YSOs is rapid variabilityof their X-ray light curves. Flare episodes of fast rise and slow decay are often observed. Inorder to pick up X-ray sources with variability, we applied a simple temporal analysis for
the Chandra sources. The XRONOS package1 was used for the following procedures.
We concentrated our temporal analysis on bright ACIS-I sources so that we can ignore
the backgrounds. Figure 7.1 shows the distribution of X-ray counts (0.5–8.0 keV) and S/N ,where S and N are the source and background counts in the 0.5–8.0 keV range. The
background counts were derived using the values in Table 4.1 and normalized by the areaof source accumulation region and the exposure time. We picked up sources with morecounts than 100 and higher S/N than 10 as the samples for temporal analysis. We hereafter
call them “bright (T)” sources, while the remaining sources are called “faint (T)” sources.
Among 278 NIR-IDed ACIS-I sources, 120 are bright (T) and 158 are faint (T).
The X-ray counts of bright (T) sources were binned with three binning sizes (100 s bin−1 ,1000 s bin−1 , and 10000 s bin−1 ) to construct light curves. These light curves were fittedwith a constant flux model. The χ2 value was derived for each fitting with
χ2 =

N
X
i=1

(i)



(i)

(i)

2

F
− Fmodel  data(i)∆Fdata

,

(i)

(7.1)

where Fdata and Fmodel are the count rate of the data and the model in the i’th time bin,(i)(i)
and ∆Fdata is the uncertainty of Fdata . The χ2 value follows the chi square distribution of1

See http://heasarc.gsfc.nasa.gov/docs/xanadu/xronos/xronos.html.

7.1. TEMPORAL ANALYSIS

133

Figure 7.1: X-ray counts (0.5–8.0 keV) and S/N (0.5–8.0 keV) of NIR-IDed ACIS-I sources. Sources withmore counts than 200 and higher S/N than 10 (120 sources) are bright (T) sources, for which the temporal
analysis was conducted. The remaining 158 sources are faint (T) sources. Variable sources among bright(T) sources are marked filled.

134

CHAPTER 7. NIR-IDED X-RAY SOURCES: (2) X-RAY PROPERTIES(N − 1) degrees of freedom; χ2N −1 (x). The upper probability for the null hypothesis (α) was
thus calculated as

α=

Z ∞
χ2

χ2N −1 (x)dx.

(7.2)

We recognized the null hypothesis (the constant count rate) is rejected; i.e., the light curveis variable, if α < 0.01 in at least one binning size. Consequently, we picked up 66 (55%)
variable light curves among bright (T) sources.
Figures 7.2–7.6 show the background-unsubtracted light curves of all the variable X-ray
sources. Note that the background count rate is less than the total count rate by more than
10 times. Many of the light curves show typical flare-like events.

Figure 7.2: Light curves of variable bright (T) NIR-IDed Chandra sources (I4–I14) with the binning of5000 s bin−1 . Light curves are plotted over the count rate (s−1 ; vertical axis) versus the time from the startof the observation (s; horizontal axis) plane.

7.1. TEMPORAL ANALYSIS

Figure 7.3: Light curves of variable bright (T) NIR-IDed Chandra sources (I20–I124).

135

136

CHAPTER 7. NIR-IDED X-RAY SOURCES: (2) X-RAY PROPERTIES

Figure 7.4: Light curves of variable bright (T) NIR-IDed Chandra sources (I125–I189).

7.1. TEMPORAL ANALYSIS

Figure 7.5: Light curves of variable bright (T) NIR-IDed Chandra sources (I194–I272).

137

138

CHAPTER 7. NIR-IDED X-RAY SOURCES: (2) X-RAY PROPERTIES

Figure 7.6: Light curves of variable bright (T) NIR-IDed Chandra sources (I280–I343).

7.2. SPECTRAL ANALYSIS

7.2

Spectral Analysis

7.2.1

Spectrum Models and Fittings

139

As almost all the NIR-IDed X-ray sources are considered to be YSOs and the X-ray emissions
from YSOs are of plasma origin (Feigelson & Montmerle 1999[53] ), we fitted the X-ray spectraof NIR-IDed sources with the mekal model convolved with the wabs model.
The mekal model implements the X-ray emissions from thermal plasma at the opticallythin limit; i.e., the plasma is transparent to its own X-ray radiation. The plasma consistsof electrons and collisionally ionized and excited atoms. When an electron is accelerated by
the electric field around an atom, it emits X-rays known as “bremsstrahlung”. When thebremsstrahlung is integrated over all electrons at a thermal equilibrium with a Maxwellian
velocity distribution, the intensity of the radiation I(E, T ) at the energy E and the plasma
temperature T is expressed as
1

I(E, T ) ∝ g(E, T )Z 2 ne ni (kB T )− 2 exp (−

E
),
kB T

(7.3)

where ne and ni are the number density of the electrons and the ions, Z is the charge of theion, and g(E, T ) is the Gaunt factor having a weak dependence on E and T . Line emissions
from excited and ionized atoms are added on the continuum radiation. The calculation ofthin-thermal plasma spectrum in the mekal model is based on Mewe, Gronenschild, & van
den Oord (1985)[127] , Mewe, Lemen, & van den Oord (1986)[128] , and Kaastra (1992)[102]with Fe L-shell line emissions improved by Liedahl, Osterheld, & Goldstein (1995)[116] . The
continuum emissions as well as line emissions from atoms (C, N, O, Ne, Na, Mg, Al, Si, S,
Ar, Ca, Fe, and Ni) are included. Free parameters of the model are the electron temperature(kB T keV), metallicity of elements (ZC , ZN , ZO , and so on), and emission measure (EM =R
ne nH dV cm−3 where ne and nH are the electron and hydrogen density and V is the emittingvolume). Given the values of kB T , EM , and the distance to the source (450 pc), the X-ray
luminosity (LX ergs s−1 ) is determined.
The wabs model implements the photoelectric absorption by cold interstellar medium
and is used to derive the amount of interstellar absorption using absorption lines in the
X-ray spectra. In most cases, C, N, and O lines in the soft X-ray band dominate fittings.
The calculation is based on the Wisconsin cross-sections that include photoelectric absorption cross-sections of major cosmic elements (Morrison & McCammon 1983[136] ). Neither

140

CHAPTER 7. NIR-IDED X-RAY SOURCES: (2) X-RAY PROPERTIES

Thomson nor Compton scattering is considered. The spectral intensity of the model (M ) at
a given energy (E) is described as
M (E) = exp (−p1 σ(E)),(7.4)

where σ(E) is the effective photoelectric absorption cross-section that is derived by converting
all the cross-sections of major elements into the hydrogen equivalent and averaging them out.
The amount of absorption (p1 ) is thus determined as the equivalent hydrogen column density(NH cm−2 ).
The cosmic abundances used in the mekal and wabs models are respectively based on
the results by Anders & Grevesse (1989)[4] and Anders & Ebihara (1982)[3] , who derived
values with meteorites and chondrites in the solar system and the solar photosphere andcorona.
The combined model of mekal and wabs is further convolved with the optics and detector
responses (Auxiliary Response Function [ARF] and Redistribution Matrix Function [RMF],
respectively). Both of ARF and RMF for Chandra/ACIS are provided by Chandra X-ray
Center. This convolution is fitted to the spectra that were constructed by binning the X-ray
photons along the energy with 20 counts bin−1 (for sources of more than 200 counts) or
10 counts bin−1 (for sources of less than 200 counts). Again, the χ2 value was calculated foreach fitting trial as


2

χ =

N
X
i=1

(i)

(i)

2

(i)

E
− Emodel⊗ARF ⊗RM F  data(i)∆Edata

,

(7.5)

(i)

where Edata and Emodel⊗ARF ⊗RM F are the spectrum intensity (s−1 keV−1 ) of backgroundsubtracted data and the convolution of the model, ARF,
q and RMF in the i’th energy bin.
(i)
(i)
(i)
∆Edata is the uncertainty of Edata and is calculated as Edata . The upper probability for thenull hypothesis (α) for the minimum χ2 value was used to discriminate whether a fitting is
acceptable or not. The XSPEC package2 was used for all these procedures.

7.2.2

One-temperature Plasma Fittings

We concentrated our spectral analysis on bright ACIS-I sources in the same way as our
temporal analysis. Figure 7.7 shows the distribution of X-ray counts (0.5–8.0 keV) and S/N(2.0–8.0 keV), which is defined as the ratio of the source and the background counts in
2

See http://heasarc.gsfc.nasa.gov/docs/xanadu/xspec/index.html.

7.2. SPECTRAL ANALYSIS

141

the 2.0–8.0 keV range. Unlike Figure 7.1, we used the S/N values in the hard band (2.0–
8.0 keV). This is because the spectrum in this energy range is important to see whether asource has hard X-ray component in addition to the soft component, nevertheless the source
spectrum can be more easily contaminated by the background spectrum in this band. We
defined “bright (S)” sources for those with more counts than 50 and larger S/N than 10 and“faint (S)” for the remaining sources among the 278 NIR-IDed ACIS-I sources. The former
consists of 142 (51%) samples while the latter of 136 (49%).

Figure 7.7: X-ray counts (0.5–8.0 keV) and S/N (2.0–8.0 keV) of NIR-IDed ACIS-I sources. Sources withmore counts than 50 and higher S/N than 10 (142 sources) are bright (S) sources, for which the spectral
analysis was conducted. Larger squares indicate sources fitted by thin-thermal plasma models; open for
one-temperature model and filled for two temperature model.

First, for bright (S) sources, we applied one-temperature thin-thermal plasma model(the mekal model) convolved with the ISM absorption (the wabs model). The metallicityof all elements is fixed to 0.3 solar based on previous works (e.g., Imanishi et al. 2001[91] ).

142

CHAPTER 7. NIR-IDED X-RAY SOURCES: (2) X-RAY PROPERTIES

When α is less than 0.05 or the best-fit parameters are unphysical (e.g., kB T > 10 keV),
we recognized that the model was rejected. Among fitted samples, 87 (61%) sources had an
acceptable fit. Using the best-fit parameters, we compiled NH , kB T , and LX in Table 7.1.
The spectra and the best-fit models of these sources are tiled in Figures 7.8–7.13.
Table 7.1: One-temperature plasma fittings of bright NIR-IDed Chandra sources
ID
I21
I27
I34
I36
I38
I54
I58
I65
I66
I67
I74
I77
I82
I83
I87
I90
I92
I93
I96
I99
I106
I109
I110
I111
I121
I124
(cont.)

countsa

S/N b

276
29.9
558
45.7
135
18.7
670
53.2
83
21.7
437
43.9
92
12.4
257
32.3
200
12.5
1232 256.5
442 168.5
835 314.7
325
14.0
109
22.8
207
23.8
116
13.0
313 157.9
574 382.2
333 1845.7
112 849.6
151
40.4
177
77.9
3013 287.9
88
16.4
259 227.2
830
40.4

NH c
(1022 cm−2 )0.00 (0.00–0.07)
0.03 (0.00–0.15)
0.00 (0.00–0.07)
0.07 (0.01–0.15)
0.72 (0.39–1.24)
0.45 (0.00–0.31)
0.40 (0.00–1.15)
0.77 (0.41–1.25)
0.09 (0.00–0.53)
0.81 (0.66–0.93)
2.25 (1.84–2.77)
3.20 (2.83–3.63)
2.67 (2.13–3.44)
0.71 (0.46–0.99)
1.93 (1.04–2.47)
0.65 (0.00–1.39)
0.55 (0.36–0.72)
0.00 (0.00–0.07)
1.93 (1.38–2.53)
2.79 (1.55–4.30)
1.46 (1.15–2.08)
0.65 (0.35–0.93)
1.23 (1.12–1.35)
0.44 (0.00–1.10)
2.69 (1.77–3.71)
0.72 (0.60–0.87)

kB T c(keV)
1.18 (1.00–1.31)
1.58 (1.34–1.79)
1.26 (0.99–1.67)
1.09 (1.01–1.22)
0.63 (0.22–0.97)
0.84 (0.98–1.42)
6.39 (2.42–79.9)
2.72 (1.67–5.06)
0.97 (0.60–1.17)
2.74 (2.35–3.45)
2.21 (1.74–2.82)
3.16 (2.51–4.13)
4.19 (2.41–6.80)
0.46 (0.30–0.67)
2.06 (1.32–3.93)
7.09 (2.79–79.9)
0.60 (0.45–0.83)
1.20 (1.00–1.12)
2.48 (1.83–3.66)
1.91 (1.19–3.75)
1.42 (1.00–1.76)
0.37 (0.22–0.69)
7.69 (6.01–10.4)
0.41 (0.11–0.88)
1.70 (1.18–3.00)
4.41 (3.80–6.03)

LX a(ergs s−1 )3.65e+29
9.84e+29
1.70e+29
1.04e+30
5.32e+29
7.04e+29
3.62e+29
1.26e+30
3.23e+29
6.36e+30
4.28e+30
1.02e+31
3.47e+30
9.44e+29
1.97e+30
5.64e+29
1.55e+30
7.16e+29
2.62e+30
1.25e+30
1.02e+30
1.70e+30
2.24e+31
2.04e+29
3.28e+30
5.04e+30

7.2. SPECTRAL ANALYSIS
ID
countsa
I125
561
I128
60
I131
662
I138
359
I140
259
I142
97
I143
143
I144
953
I145
73
I147
2276
I148
673
I149
109
I153
142
I154
97
I155
76
I158
838
I164
507
I165
833
I166
415
I167
921
I170
164
I173
59
I174
1908
I178
83
I179
363
I181
144
I187
544
I192
324
I197
878
I198
83
I202
88
I204
289
I208
270
(cont.)

S/N b
54.9
62.7
83.3
66.0
689.2
36.9
55.8
187.5
32.9
117.4
125.0
1204.9
141.8
182.1
229.1
1617.22778.64039.798.2
2759.8
10.4
298.2
263.3
20.3
16.9
1437.5
156.1
355.7
790.1
71.1
22.2
120.3
775.9

143
NH c
0.33 (0.19–0.51)
12.7 (0.46–49.2)
0.10 (0.00–0.23)
3.22 (2.21–4.28)
6.22 (4.36–12.4)
11.6 (3.75–21.1)
1.60 (0.88–2.41)
1.68 (1.48–1.89)
0.00 (. . . .–. . . .)1.04 (0.95–1.15)
0.50 (0.32–0.65)
5.32 (3.23–9.10)
1.38 (1.11–2.21)
1.91 (1.23–3.54)
7.90 (. . . .–. . . .)0.49 (0.20–0.42)
2.06 (1.71–2.46)
1.40 (1.14–1.70)
0.77 (0.65–0.92)
0.45 (0.31–0.57)
0.50 (0.16–0.99)
1.64 (. . . .–. . . .)0.00 (0.00–0.02)
0.21 (0.00–1.01)
0.43 (0.28–0.53)
2.97 (1.39–4.70)
0.00 (0.00–0.06)
0.64 (0.32–0.82)
0.01 (0.00–0.05)
0.18 (0.00–1.02)
2.82 (1.43–4.57)
1.97 (1.50–2.51)
1.46 (1.02–2.30)

kB T c3.25 (2.34–4.59)
3.05 (0.72–79.9)
3.19 (2.35–4.48)
7.52 (3.54–79.9)
3.12 (1.32–5.84)
1.07 (0.54–3.56)
2.99 (1.77–6.40)
2.55 (2.13–3.10)
1.00 (. . . .–. . . .)2.78 (2.45–3.20)
2.76 (2.17–3.93)
1.48 (0.75–3.02)
0.88 (0.43–1.13)
2.30 (1.18–4.34)
1.99 (. . . .–. . . .)1.09 (1.19–1.46)
1.80 (1.48–2.27)
4.78 (3.34–7.87)
0.30 (0.23–0.48)
3.12 (2.56–4.13)
7.01 (3.40–36.9)
2.92 (. . . .–. . . .)1.30 (1.24–1.34)
8.93 (2.16–79.9)
0.61 (0.51–0.74)
7.54 (2.94–79.9)
1.24 (1.06–1.32)
0.94 (0.78–1.14)
1.38 (1.30–1.60)
0.76 (0.14–1.11)
2.00 (1.07–3.55)
2.62 (1.83–3.40)
4.24 (2.10–21.9)

LX a
1.96e+30
1.55e+31
1.42e+30
3.96e+30
6.32e+30
4.84e+30
1.03e+30
8.08e+30
8.76e+28
1.46e+31
2.68e+30
5.84e+30
1.73e+30
7.64e+29
1.27e+30
1.96e+30
4.52e+30
5.48e+30
7.36e+30
3.37e+30
6.08e+28
3.74e+29
2.74e+30
2.82e+29
1.59e+30
1.23e+30
7.84e+29
1.34e+30
1.29e+30
1.61e+29
1.04e+30
2.28e+30
1.95e+30

144

CHAPTER 7. NIR-IDED X-RAY SOURCES: (2) X-RAY PROPERTIES
ID
I212
I213
I216
I217
I218
I219
I229
I223
I232
I234
I237
I243
I246
I251
I261
I263
I264
I272
I274
I279
I280
I282
I293
I297
I299
I303
I317
I322

countsa S/N b
NH c
kB T cLX a
345 1727.6 3.67 (2.60–5.00) 2.35 (1.60–3.89) 4.16e+30
326 504.9 3.16 (2.18–4.27) 2.02 (1.38–3.49) 4.20e+30
17225.9 0.17 (0.00–0.46) 1.02 (0.88–1.32) 3.06e+2950
12.1 0.43 (0.00–2.34) 3.15 (0.81–79.9) 1.65e+291228 448.2 3.63 (3.24–4.10) 3.10 (2.49–3.95) 1.80e+31
89 366.8 1.31 (0.00–3.11) 1.50 (0.87–7.35) 6.60e+29
157
16.1 0.88 (0.01–0.33) 1.06 (1.70–3.35) 4.28e+281424 1291.3 0.07 (0.04–0.11) 1.22 (1.02–1.28) 2.20e+30
213
13.0 1.47 (0.94–2.18) 1.75 (1.14–2.87) 1.52e+30
222
32.2 1.15 (0.85–1.73) 1.49 (1.00–2.84) 1.30e+30
9122.2 0.46 (0.14–0.99) 0.42 (0.12–0.65) 4.52e+30
187 170.8 0.00 (0.00–0.11) 1.20 (1.04–1.40) 2.23e+296337.8 2.51 (0.46–7.60) 5.68 (1.43–79.9) 6.12e+29
175
57.5 2.08 (1.44–2.84) 3.14 (2.06–5.65) 1.41e+30
646
21.0 0.50 (0.37–0.65) 8.64 (5.85–17.9) 3.08e+30
223 140.6 1.48 (0.50–2.03) 1.26 (0.83–4.09) 1.97e+30
346 1681.7 7.14 (3.82–10.7) 5.48 (3.05–79.9) 5.56e+30507
43.1 0.00 (0.00–0.04) 1.75 (1.57–2.21) 8.48e+2920943.6 0.59 (0.36–0.99) 0.62 (0.80–1.31) 2.78e+29
114 304.4 4.00 (2.16–6.27) 2.52 (1.37–5.85) 1.36e+30
943 260.1 0.33 (0.21–0.43) 2.70 (2.24–3.50) 3.42e+3090882.1 0.02 (0.00–0.08) 1.02 (0.95–1.08) 1.24e+30
518
55.1 0.54 (0.30–0.75) 3.01 (2.14–5.36) 2.26e+30
1048
96.8 0.53 (0.43–0.59) 3.45 (2.91–4.36) 4.48e+30
198
17.7 0.03 (0.00–0.14) 1.35 (1.16–1.70) 8.96e+28
75
17.9 0.66 (0.00–1.23) 0.98 (0.46–3.07) 3.28e+30657
13.9 0.00 (0.00–0.05) 1.30 (1.22–1.38) 1.09e+30288
16.1 0.34 (0.00–0.16) 0.68 (0.84–1.07) 3.78e+29

a Values in the 0.5–8.0 keV range.
b Values in the 2.0–8.0 keV range.
c The lower and upper limit (1 σ) are given in parentheses. Three sources (I145, I155, and I173) have too few spectral bins toderive the uncertainty of their best-fit parameters.

7.2. SPECTRAL ANALYSIS

145

Figure 7.8: Spectra and the best-fit models of one-temperature thin-thermal plasma fittings of bright (S)NIR-IDed Chandra sources (I21–I77). The metallicity of all elements is fixed to be 0.3 solar. In the upper
panels, the data (pluses) and the best-fit model (solid steps) are plotted over the energy (keV; horizontalaxis) versus normalized spectral intensity (count rate keV−1 ; vertical axis) plane. The response functionsof the optics and the detector are convolved into the model. In the lower panels, the residuals between the
background-subtracted data and the best-fit model are plotted over the energy (keV; horizontal axis) versus
(i)
(i)
(i)
χ(i) = (Edata − Emodel⊗ARF ⊗RM F )/∆Edata (vertical axis) plane.

146

CHAPTER 7. NIR-IDED X-RAY SOURCES: (2) X-RAY PROPERTIES

Figure 7.9: Spectra and the best-fit models of one-temperature thin-thermal plasma fittings of bright (S)NIR-IDed Chandra sources (I82–I125).

7.2. SPECTRAL ANALYSIS

147

Figure 7.10: Spectra and the best-fit models of one-temperature thin-thermal plasma fittings of bright (S)NIR-IDed Chandra sources (I128–I158).

148

CHAPTER 7. NIR-IDED X-RAY SOURCES: (2) X-RAY PROPERTIES

Figure 7.11: Spectra and the best-fit models of one-temperature thin-thermal plasma fittings of bright (S)NIR-IDed Chandra sources (I164–I202).

7.2. SPECTRAL ANALYSIS

149

Figure 7.12: Spectra and the best-fit models of one-temperature thin-thermal plasma fittings of bright (S)NIR-IDed Chandra sources (I204–I246).

150

CHAPTER 7. NIR-IDED X-RAY SOURCES: (2) X-RAY PROPERTIES

Figure 7.13: Spectra and the best-fit models of one-temperature thin-thermal plasma fittings of bright (S)NIR-IDed Chandra sources (I251–I322).

7.2. SPECTRAL ANALYSIS

7.2.3

151

Two-temperature Plasma Fittings

Second, for 55 bright (S) sources that rejected one-temperature plasma model, we applied
two-temperature plasma model (two mekal models with different temperatures) convolved
with wabs, resulting 32 (23%) sources to have an acceptable fit with α ≥ 0.05. Bothcomponents were assumed to have the same NH value. The metallicity of all elements wasagain fixed to 0.3 solar. In Table 7.2, we compiled the best-fit values of kB T and LX of thehigher temperature component (kB T 1 and LX1 ) as well as those of the lower temperaturecomponent (kB T 2 and LX2 ) along with NH and the total LX of both components. The
spectra and the best-fit models are tiled in Figures 7.15–7.17.
We still have 23 bright (S) sources not to be fitted with either one-temperature or twotemperature plasma models with 0.3 solar metallicity. Nine sources, which were globally wellfitted with two-temperature plasma model, show excess emission lines that decrease the αvalue. We therefore fitted these spectra with two-temperature plasma model with variable
metallicity for elements with prominent line emissions (two vmekal models), resulting that
all of them have an acceptable fit. Table 7.3 lists the best-fit values of continuum emissions(kB T and LX values of the higher and lower temperature component, NH and the total LX ),while Table 7.4 shows the best-fit values of line emissions (the metallicity of each element).
The spectra and the best-fit models are given in Figure 7.18.

A (87)B (32)C (9)

D (14)

Figure 7.14: Breakdown of best-fit models of 142 bright (S) NIR-IDed ACIS-I sources. A and B are forthe spectra fitted with one-temperature and two-temperature plasma model with the metallicity fixed to be
0.3 solar, while C is for the spectra fitted with two-temperature plasma with variable metallicity values. D
is for those fitted by none of these models. The number of sources are shown in parentheses.

I7
I12
I14
I17
I25
I31
I42
I47
I71
I85
I130
I150
I151
I189
I194
I200
I211
I225
I238
I240
I248
I256
(cont.)

ID

S/N b

549
18.8
361
16.3
579
21.3
534
17.5
2287
59.5
740 169.2
1023
89.9
1771 828.8
1191 814.1
1088 471.3
165
26.8
2201 1080.8
14667 2164.2761
95.0
1411 741.5
3840 1896.2
711
12.6
1189
22.9
311
11.5
2772
60.7
2062 707.9
1143
19.7

countsa

NH c(1022 cm−2 )0.02 (0.00–0.15)
0.00 (0.00–0.23)
0.00 (0.00–0.04)
0.00 (0.00–0.14)
0.00 (0.00–0.02)
0.80 (0.54–1.34)
0.90 (0.62–1.07)
0.36 (0.27–0.48)
0.08 (0.02–0.12)
0.02 (0.00–0.07)
1.00 (0.69–1.15)
0.22 (0.16–0.27)
0.33 (0.31–0.35)
0.00 (0.00–0.11)
0.26 (0.18–0.36)
0.01 (0.00–0.03)
0.26 (0.17–0.36)
0.23 (0.16–0.26)
0.47 (0.21–1.01)
0.43 (0.37–0.50)
0.24 (0.19–0.32)
0.85 (0.35–1.03)

kB T cd
1(keV)
1.68 (1.34–3.26)
3.15 (0.66–13.8)
3.49 (2.27–9.44)
1.94 (1.44–2.77)
4.61 (2.48–13.0)
1.24 (1.01–1.41)
1.31 (1.22–1.56)
2.45 (2.13–3.07)
2.03 (1.15–4.66)
4.05 (2.40–6.40)
2.93 (1.46–50.1)
8.28 (3.86–79.9)
2.80 (2.52–3.34)
1.47 (1.34–1.75)
3.14 (1.73–6.20)
2.45 (2.00–2.75)
5.67 (3.29–15.8)
5.72 (3.76–7.12)
0.71 (0.45–0.84)
2.53 (1.97–3.32)
3.01 (2.52–3.61)
3.57 (2.80–5.29)

LX ad1(ergs s−1 )4.04e+29
5.56e+29
7.04e+29
5.68e+29
1.61e+30
2.51e+30
8.48e+29
3.66e+30
9.44e+29
2.36e+30
2.78e+29
1.26e+30
2.61e+31
8.76e+29
1.80e+30
2.94e+30
2.22e+30
4.36e+30
9.88e+29
5.40e+30
3.67e+30
4.04e+30

kB T ce2(keV)
0.74 (0.60–0.86)
1.04 (0.63–1.37)
0.88 (0.76–1.06)
0.77 (0.58–0.87)
1.00 (0.87–1.06)
0.13 (0.09–0.15)
0.10 (0.09–0.18)
0.84 (0.71–1.03)
0.79 (0.67–0.87)
1.05 (0.81–1.27)
0.21 (0.14–1.09)
0.84 (0.78–0.88)
1.10 (1.06–1.21)
0.55 (0.41–0.70)
1.04 (0.79–1.14)
0.87 (0.83–0.91)
1.21 (1.06–1.34)
1.00 (0.84–1.11)
0.10 (0.08–0.21)
1.02 (0.83–1.10)
0.85 (0.76–0.97)
0.62 (0.48–1.10)

LX ae
2(ergs s−1 )2.67e+29
1.88e+29
3.34e+29
2.80e+29
2.24e+30
5.68e+31
2.26e+30
1.90e+30
1.06e+30
1.74e+30
8.48e+30
4.00e+30
1.94e+31
2.37e+29
1.76e+30
3.17e+30
1.04e+30
9.32e+29
5.88e+30
5.00e+30
1.97e+30
4.60e+30

Table 7.2: Two-temperature plasma fittings of bright NIR-IDed Chandra sources (1)
LX af
1+2
(ergs s−1 )6.71e+29
7.44e+29
1.04e+30
8.48e+29
3.85e+30
5.93e+31
3.11e+30
5.56e+30
2.00e+30
4.10e+30
8.76e+30
5.26e+30
4.55e+31
1.11e+30
3.56e+30
6.11e+30
3.26e+30
5.29e+30
6.87e+30
1.04e+31
5.64e+30
8.64e+30

152
CHAPTER 7. NIR-IDED X-RAY SOURCES: (2) X-RAY PROPERTIES

countsa
270
312
298
279
825
660
617
2262
5270
695

S/N b
11.4
13.0
159.8
52.4
141.5
97.8
11.2
168.3
757.1
17.8

NH c
0.21 (. . . .–. . . .)0.66 (0.35–0.92)
0.25 (0.00–1.08)
0.03 (0.00–0.82)
0.35 (0.23–0.45)
1.04 (0.74–1.28)
0.08 (0.03–0.21)
0.00 (0.00–0.04)
0.09 (0.07–0.11)
0.21 (0.08–0.41)

kB T cd
16.89 (. . . .–. . . .)1.11 (0.38–0.63)
2.21 (1.52–4.26)
1.38 (1.04–1.80)
2.80 (1.80–5.16)
2.82 (2.11–4.45)
3.79 (1.91–5.78)
2.41 (1.90–3.23)
2.92 (2.71–3.40)
2.66 (1.76–10.4)

LX ad1
3.67e+29
4.56e+29
7.20e+29
3.14e+29
2.39e+30
2.42e+30
8.44e+29
2.99e+30
8.48e+30
8.84e+29

kB T ce20.63 (. . . .–. . . .)0.21 (0.08–0.30)
0.18 (0.08–11.2)
0.35 (0.18–0.68)
1.06 (0.71–1.41)
0.85 (0.60–1.06)
0.95 (0.76–1.05)
0.95 (0.80–1.05)
0.99 (0.86–1.06)
0.65 (0.57–0.83)

LX ae
2
3.42e+29
1.09e+30
6.28e+29
1.39e+29
1.22e+30
2.28e+30
5.44e+29
9.96e+29
3.25e+30
9.72e+29

f The total luminosity of two components is given.

e Best-fit parameters of the lower temperature component are given.

d Best-fit parameters of the higher temperature component are given.

c The lower and upper limit (1 σ) are given in parentheses. I278 has too few spectral bins to derive the uncertainty of its best-fit parameters.

b Values in the 2.0–8.0 keV range.

a Values in the 0.5–8.0 keV range.

ID
I278
I287
I289
I298
I308
I313
I314
I319
I324
I326

LX af
1+2
7.09e+29
1.55e+30
1.35e+30
4.53e+29
3.61e+30
4.70e+30
1.39e+30
3.99e+30
1.17e+31
1.86e+30

7.2. SPECTRAL ANALYSIS
153

154

CHAPTER 7. NIR-IDED X-RAY SOURCES: (2) X-RAY PROPERTIES

Figure 7.15: Spectra and the best-fit models of two-temperature thin-thermal plasma fittings of bright (S)NIR-IDed Chandra sources (I7–I150). The metallicity of all elements is fixed to be 0.3 solar. In the upper panels, the data (pluses) and the best-fit model (solid steps) are plotted over the energy (keV; horizontal axis) versus normalized spectral intensity (count rate keV−1 ; vertical axis) plane. The dashedand dashed-and-dotted steps represent each spectral component. The response functions of the optics and the detector are convolved into the model. In the lower panels, the residuals between the
background-subtracted data and the best-fit model are plotted over the energy (keV; horizontal axis) versus
(i)
(i)
(i)
χ(i) = (Edata − Emodel⊗ARF ⊗RM F )/∆Edata (vertical axis) plane.

7.2. SPECTRAL ANALYSIS

155

Figure 7.16: Spectra and the best-fit models of two-temperature thin-thermal plasma fittings of bright (S)NIR-IDed Chandra sources (I151–I308).

156

CHAPTER 7. NIR-IDED X-RAY SOURCES: (2) X-RAY PROPERTIES

Figure 7.17: Spectra and the best-fit models of two-temperature thin-thermal plasma fittings of bright (S)NIR-IDed Chandra sources (I313–I326).

1747
25400
2221
320
3603
1348
7968
4600
1399

I13
I51
I283
I295
I328
I339
I342
I343
I346

133.5
13166.7
1102.3
26.5
82.1
58.4
368.7
228.6
33.4

S/N b

NH c
22
(10 cm−2 )0.02 (0.00–0.10)
0.20 (0.18–0.22)
0.04 (0.00–0.09)
0.05 (0.00–0.38)
0.07 (0.04–0.12)
0.04 (0.00–0.09)
0.10 (0.08–0.13)
0.21 (0.17–0.27)
0.02 (0.00–0.11)

kB T cd
1(keV)
3.29 (2.73–4.06)
2.90 (2.79–3.09)
3.27 (2.55–4.37)
3.43 (2.48–8.55)
1.85 (1.45–1.72)
2.38 (1.85–5.58)
2.29 (2.12–2.51)
1.97 (1.82–2.14)
2.11 (1.72–2.55)

Na(solar)
0.3
0.3
0.3
0.3
0.3
0.3
5.15 (0.00–12.7)
41.3 (24.3–73.8)
0.3

kB T ce2(keV)
0.70 (0.63–0.79)
0.73 (0.65–0.87)
1.00 (0.81–1.23)
0.82 (0.60–0.96)
0.67 (0.34–0.51)
0.95 (0.76–1.11)
0.67 (0.61–0.75)
0.64 (0.57–0.69)
0.73 (0.63–0.85)

LX ae
2(ergs s−1 )8.48e+29
6.84e+30
7.04e+29
1.43e+29
2.38e+30
8.24e+29
5.12e+30
5.20e+30
8.64e+29

Oa(solar)0.80 (0.30–1.76)
0.3
0.3
0.3
0.21 (0.05–0.28)
0.3
0.3
0.3
0.3

Nea
(solar)0.26 (0.00–0.85)
1.52 (0.80–2.01)
0.3
0.66 (0.00–)
1.05 (0.59–1.25)
0.37 (0.00–1.72)
1.05 (0.82–1.31)
1.38 (0.88–2.12)
1.34 (0.12–2.57)

Mga(solar)0.3
0.3
1.86 (0.41–5.13)
0.89 (0.00–)
0.31 (0.10–0.57)
0.3
0.3
0.3
0.3

Sia
(solar)0.3
0.31 (0.15–0.39)
0.3
0.3
0.3
0.3
0.3
0.3
0.3

Ara
(solar)0.3
0.78 (0.18–1.38)
0.3
0.3
0.3
0.3
0.40 (0.00–1.14)
0.3
0.3

LX af
1+2
(ergs s−1 )3.37e+30
6.80e+31
4.53e+30
6.34e+29
6.54e+30
2.47e+30
1.95e+31
1.35e+31
2.36e+30

Sa(solar)0.3
0.93 (0.69–1.19)
2.57 (1.17–5.17)
0.3
0.3
0.3
0.55 (0.29–0.82)
0.3
0.3

a The lower and upper limit (1 σ) are given in parentheses for free parameters. Others are fixed to be 0.3 solar.

I13
I51
I283
I295
I328
I339
I342
I343
I346

ID

LX ad
1
(ergs s−1 )2.52e+30
6.12e+31
3.83e+30
4.92e+29
4.16e+30
1.65e+30
1.44e+31
8.28e+30
1.50e+30

Table 7.4: Two-temperature plasma fittings of bright NIR-IDed Chandra sources (3)f The total luminosity of two components is given.

e Best-fit parameters of the lower temperature component are given.

d Best-fit parameters of the higher temperature component are given.

c The lower and upper limit (1 σ) are given in parentheses.

b Values in the 2.0–8.0 keV range.

a Values in the 0.5–8.0 keV range.

countsaID

Table 7.3: Two-temperature plasma fittings of bright NIR-IDed Chandra sources (2)Fea(solar)0.29 (0.15–0.53)
0.26 (0.20–0.32)
0.82 (0.30–1.93)
1.05 (0.41–)
0.13 (0.06–0.16)
0.25 (0.18–0.39)
0.13 (0.09–0.19)
0.36 (0.26–0.55)
0.30 (0.14–0.53)

7.2. SPECTRAL ANALYSIS
157

158

CHAPTER 7. NIR-IDED X-RAY SOURCES: (2) X-RAY PROPERTIES

Figure 7.18: Spectra and the best-fit models of two-temperature thin-thermal plasma fittings of bright (S)NIR-IDed Chandra sources (I13–I346). The metallicity of all elements is fitted for elements with prominentline emissions. In the upper panels, the data (pluses) and the best-fit model (solid steps) are plotted over theenergy (keV; horizontal axis) versus normalized spectral intensity (count rate keV−1 ; vertical axis) plane.
The dashed and dashed-and-dotted steps represent each spectral component. The response functions of
the optics and the detector are convolved into the model. In the lower panels, the residuals between the
background-subtracted data and the best-fit model are plotted over the energy (keV; horizontal axis) versus
(i)
(i)
(i)
χ(i) = (Edata − Emodel⊗ARF ⊗RM F )/∆Edata (vertical axis) plane.

7.2. SPECTRAL ANALYSIS

7.2.4

159

Time-sliced Spectroscopy

Finally, we conducted the time-sliced spectroscopy of the bright variable sources. We confined
this analysis to those with flare-like variability and more counts than 500 in each slice. Six
sources (I25, I51, I110, I200, I248, and I324) meet these criteria. We sliced their light curves(Figs. 7.19 and 7.20) into flare and quiescent phases, and fitted the spectrum of each slicewith thin-thermal plasma models. Both slices of I110 were well fitted with one-temperatureplasma model. Other slices were not fitted with one-temperature plasma with α < 0.05 ora systematic residual, so two-temperature plasma model was used to fit these spectra. The
best-fit values are summarized in Table 7.5.

(1)

(2)

(1)

(2)

Figure 7.19: Time-sliced spectroscopy of some bright variable NIR-IDed Chandra sources (I25–I51). The
light curves and the time slices are in the panels of the left column. The time-sliced spectra and the best-fit
models of thin-thermal plasma fittings are in the middle and the right column. The metallicity of all elements
is fixed to be 0.3 solar. In the upper panels, the data (pluses) and the best-fit model (solid steps) are plotted
over the energy (keV; horizontal axis) versus normalized spectral intensity (count rate keV−1 ; vertical axis)
plane. The dashed and dashed-and-dotted steps represent each spectral component. The response functionsof the optics and the detector are convolved into the model. In the lower panels, the residuals between the
background-subtracted data and the best-fit model are plotted over the energy (keV; horizontal axis) versus
(i)
(i)
(i)
χ(i) = (Edata − Emodel⊗ARF ⊗RM F )/∆Edata (vertical axis) plane.

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CHAPTER 7. NIR-IDED X-RAY SOURCES: (2) X-RAY PROPERTIES

(1)

(2)

(1)

(2)

(1)

(2)

(1)

(2)

Figure 7.20: Time-sliced spectroscopy of some bright variable NIR-IDed Chandra sources (I110–I324).

1 (Q)
2 (F)
1 (Q)
2 (F)
1 (F)
2 (F)
1 (Q)
2 (F)
1 (Q)
2 (F)
1 (F)
2 (Q)

phasea

715
1572
13470
11930
1154
1859
2037
1803
511
1551
2495
2775

countsb
NH c(10 cm−2 )0.00 (0.00–0.06)
0.01 (0.00–0.04)
0.19 (0.17–0.20)
0.20 (0.18–0.23)
1.52 (1.29–1.77)
1.03 (0.91–1.15)
0.04 (0.00–0.08)
0.00 (0.00–0.03)
0.20 (0.04–0.78)
0.22 (0.14–0.32)
0.07 (0.05–0.10)
0.11 (0.08–0.16)
22

kB T cd
1(keV)
9.71 (0.21–79.9)
4.83 (2.61–8.77)
3.28 (3.01–3.60)
3.23 (2.95–3.53)
6.82 (4.59–12.0)
7.89 (5.85–11.6)
2.65 (1.73–9.42)
2.27 (1.86–2.83)
2.52 (0.50–27.4)
3.07 (2.53–3.79)
3.17 (2.61–3.99)
2.63 (1.96–3.26)

e Best-fit parameters of the lower temperature component are given.

d Best-fit parameters of the higher temperature component are given.

c The lower and upper limit (1 σ) are given in parentheses.

b Values in the 0.5–8.0 keV range.

a Q for the quiescent phases and F for the flare phases.

I324

I248

I200

I110

I51

I25

ID

EM1d
(cm−3 )
3.71 (1.04–9.14) e+52
1.79 (1.12–2.50) e+53
4.66 (4.28–24.6) e+54
5.04 (4.62–25.0) e+54
2.55 (2.20–3.07) e+54
1.11 (1.02–1.23) e+54
1.35 (0.70–2.03) e+53
4.32 (3.59–5.29) e+53
1.95 (0.77–4.08) e+53
3.82 (3.08–4.42) e+53
8.73 (7.21–10.2) e+53
6.70 (5.31–8.60) e+53

kB T ce2(keV)
0.92 (0.18–0.98)
1.04 (0.91–1.11)
1.01 (0.91–1.10)
0.94 (0.84–1.01)...............
...............
0.87 (0.83–0.93)
0.84 (0.75–0.90)
0.92 (0.73–1.12)
0.85 (0.74–1.01)
1.00 (0.84–1.11)
0.98 (0.80–1.08)

Table 7.5: Time-sliced spectroscopy of bright NIR-IDed Chandra sources (1)EM2e(cm−3 )
2.15 (0.07–2.50) e+53
2.78 (2.01–3.49) e+53
1.23 (0.92–1.52) e+54
1.14 (0.88–1.46) e+54.....................
.....................
4.19 (3.45–4.98) e+53
2.73 (2.05–3.32) e+53
1.91 (0.89–7.43) e+53
1.84 (1.17–2.90) e+53
3.27 (2.20–4.59) e+53
3.80 (2.63–5.06) e+53

7.2. SPECTRAL ANALYSIS
161

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CHAPTER 7. NIR-IDED X-RAY SOURCES: (2) X-RAY PROPERTIES

7.3

Relations between Parameters

7.3.1

X-ray absorption versus NIR extinction

We examined the relation between AV and NH . The former reflects the amount of ISM in
the solid-state, while the latter reflects that in any states. The AV values were determinedfrom the NIR color-magnitude diagram (Fig. 6.7) and the NH values were from the X-ray
spectral fittings (Tables 7.1, 7.2, and 7.3). We have 118 sources with AV and NH values, forwhich we fitted with a linear relation in Figure 7.21 to obtainµNH
21
10 cm−2Ã¶= 1.60+0.18−0.15 ×

!

AV
.
mag

(7.6)

The slope of 1.60+0.18−0.15 is smaller than that of the Galactic interstellar medium (1.79; Predehl[154]& Schmitt 1995 ) and is comparable to the values obtained in the ρ Ophiuchi dark cloud(1.59±0.40; Imanishi et al. 2001[91] ).

7.3.2

X-ray counts versus X-ray flux

The relation between X-ray counts and the flux (FX ) in the 0.5–8.0 keV range was examinedusing bright (S) samples. The linear relation of
Ã

FX
log
ergs s−1 cm−2!

= log (counts) − 16.1

(7.7)

(Figure 7.22) was used to estimate the detection limit of the Chandra observation (Sect. 5.1)
and the expected number of background sources (Sect. 8.1).

7.3.3

X-ray counts versus X-ray luminosity

To estimate the LX values of faint (S) sources, we examined the relation between the X-ray
counts and luminosity (LX ) in the 0.5–8.0 keV range of bright (S) sources (Fig. 7.23). The
linear relation was derived to be
Ã

LX
log
ergs s−1!

= log (counts) + 27.6.

(7.8)

7.3. RELATIONS BETWEEN PARAMETERS

163

Figure 7.21: Relation between X-ray absorption (NH ) and visual extinction (AV ) for NIR-IDed Chandra
sources. The NH values are derived from fitting the X-ray spectra, while AV values are from the colormagnitude diagram (Fig. 6.7). The best-fit linear relation is shown with the dashed line.

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CHAPTER 7. NIR-IDED X-RAY SOURCES: (2) X-RAY PROPERTIES

Figure 7.22: Relation between X-ray counts and X-ray flux (FX ) for NIR-IDed bright (S) sources. The
best-fit linear relation is shown with the dashed line.

7.3. RELATIONS BETWEEN PARAMETERS

165

Figure 7.23: Relation between X-ray counts and X-ray luminosity (LX ) for NIR-IDed bright (S) sources.
The best-fit linear relation is shown with the dashed line.

166

CHAPTER 7. NIR-IDED X-RAY SOURCES: (2) X-RAY PROPERTIESChapter 8
NIR-unIDed X-ray Sources
Contents
8.1

8.2

8.3

8.4

The Nature of NIR-unIDed X-ray Sources . . . . . . . . . . . . 168
8.1.1

Background AGNs . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

8.1.2

Sources with YSO-like Features . . . . . . . . . . . . . . . . . . . . 175

H2 Imaging Observations on OMC-3 . . . . . . . . . . . . . . . . 177
8.2.1

Observation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177

8.2.2

Analysis & Results . . . . . . . . . . . . . . . . . . . . . . . . . . . 178

NIR Observations on MMS 2 and MMS 3 . . . . . . . . . . . . 178
8.3.1

Observation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178

8.3.2

Analysis & Results . . . . . . . . . . . . . . . . . . . . . . . . . . . 181

8.3.3

Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187

Centimeter Observations on MMS 2 and MMS 3 . . . . . . . . 188
8.4.1

Observation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188

8.4.2

Analysis & Results . . . . . . . . . . . . . . . . . . . . . . . . . . . 189

8.4.3

Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190

167

168

CHAPTER 8. NIR-UNIDED X-RAY SOURCES

In this chapter, we discuss the nature of NIR-unIDed Chandra sources. In Sect. 8.1,
we conclude that most of the NIR-unIDed sources are background AGNs based on the
spectral analysis of some bright sources, their HR, and spatial distribution. There remaina dozen of exceptions, however, that have YSO-like features among NIR-unIDed sources.
Some have a softer HR than AGNs and an association with cloud cores. These X-ray
emissions are compared with the H2 image of OMC-3 that we obtained with QUIRC on
UH88 (Sect. 8.2). We found that some NIR-unIDed sources are located at 1.3 mm cloud
cores and are associated with H2 outflows. As a test case, we studied the X-ray emissions at
MMS 2 and MMS 3 with follow-up observations in the NIR (Sect. 8.3) and the centimeter(Sect. 8.4) band respectively using Subaru and VLA. The nature of NIR and centimetersources is discussed in each section, which gives vital clues to discuss the origin of these
X-ray emissions in Chap. 9.

8.1

The Nature of NIR-unIDed X-ray Sources

8.1.1

Background AGNs

We have 107 Chandra ACIS-I sources that were identified with neither 2MASS nor QUIRC
sources. Most of these sources are too faint to conduct temporal and spectral analyses unlike
NIR-IDed sources, which makes it difficult to discuss their nature on a source basis. However,on the following arguments, we consider that most, if not all, of these NIR-unIDed sources
are background AGNs.
First, we fitted the spectra of NIR-unIDed bright (S) sources with a power-law model;
M (E) ∝ E −Γ ,(8.1)

convolved with the ISM absorption. NIR-unIDed bright (S) sources were defined in Figure 8.1
with the same criteria for NIR-IDed bright (S) sources (Fig. 7.7). Fifteen (14%) sources were
found to be bright (S), while 92 (86%) were faint (S).
All of the bright (S) sources were well fitted with a power-law model, with the upperprobability of α > 0.05. Photons in the 1.0–8.0 keV range were used. Using the best-fit
parameters, we derived NH , the photon index (Γ), and FX in Table 8.1. The spectra and thebest-fit models are shown in Figures 8.2 and 8.3.

8.1. THE NATURE OF NIR-UNIDED X-RAY SOURCES

169

Figure 8.1: X-ray counts (0.5–8.0 keV) and S/N (2.0–8.0 keV) of NIR-unIDed ACIS-I sources. Sources
with more counts than 50 and higher S/N than 10 (15 sources) are bright (S) sources, for which the spectral
analysis was conducted.

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CHAPTER 8. NIR-UNIDED X-RAY SOURCES

The AGNs generally show the power-law index of Γ ∼ 1.7 in the X-ray band regardlessof their types and luminosities (Charles & Seward 1995[33] ). Most spectra are consistent
with that of a typical AGN. Moreover, when fitted with a thin-thermal plasma model, many
spectra had the unphysical best-fit values of kB T > 15 keV. These indicate that the X-ray
emissions from these bright (S) sources are from mostly AGNs, not from YSOs.

Table 8.1: Power-law fittings of NIR-unIDed Chandra sources

IDa

countsb

S/N c

I3†
I11†
I19†
I22†
I23†
I50
I98
I186
I266
I275
I301
I325†
I330
I336†
I345†

368
110
103
55
98
54
62
66
53
66
113
74
67
88
258

10.6
34.1
35.0
12.8
48.7
30.3
586.2
615.8
22.4
56.7
194.8
35.0
22.8
10.9
13.5

NH d
(1022 cm−2 )1.43 (0.74–2.00)
1.40 (0.05–3.48)
1.21 (0.00–3.20)
0.91 (0.00–5.27)
1.74 (0.00–4.63)
2.27 (0.00–7.29)
2.08 (. . . .–. . . .)1.34 (0.00–45.8)
2.91 (. . . .–. . . .)16.2 (. . . .–. . . .)3.68 (1.32–6.57)
1.16 (0.00–5.61)
7.15 (2.98–13.1)
0.84 (0.00–2.85)
0.47 (0.00–1.10)

Γd0.51 (0.17–0.98)
1.10 (0.14–2.11)
1.58 (0.52–2.94)
1.09 (−0.16–4.01)
1.35 (0.04–2.78)
2.11 (0.07–6.18)
2.01 ( . . . . – . . . . )0.99 (−0.54–10.0)
0.92 ( . . . . – . . . . )1.30 ( . . . . – . . . . )2.40 (1.65–3.60)
0.87 (−0.33–3.22)
4.36 (2.30–7.84)
0.98 (−0.11–1.65)
0.66 (0.09–0.88)

FX b(ergs s−1 cm−2 )9.74e−14
2.90e−14
1.87e−14
1.13e−14
2.18e−14
9.25e−15
1.46e−14
2.64e−14
1.98e−14
2.92e−14
2.41e−14
1.97e−14
1.03e−14
1.59e−14
5.96e−14

a Sources that are rejected to have a thin-thermal plasma spectrum are marked with † .
b Values in the 0.5–8.0 keV range.
c Values in the 2.0–8.0 keV range.
d The lower and upper limit (1 σ) are given in parentheses.

Three sources (I98, I266, and I275) have too few
spectral bins to derive the uncertainty of their best-fit parameters.

8.1. THE NATURE OF NIR-UNIDED X-RAY SOURCES

171

Figure 8.2: Spectra and the best-fit power-law models of NIR-unIDed bright (S) Chandra sources (I3–I325).
In the upper panels, the data (pluses) and the best-fit model (solid steps) are plotted over the energy (keV;
horizontal axis) versus normalized spectral intensity (count rate keV−1 ; vertical axis) plane. The response
functions of the optics and the detector are convolved into the model. In the lower panels, the residuals
between the background-subtracted data and the best-fit model are plotted over the energy (keV; horizontal
(i)
(i)
(i)
axis) versus χ(i) = (Edata − Emodel⊗ARF ⊗RM F )/∆Edata (vertical axis) plane.

172

CHAPTER 8. NIR-UNIDED X-RAY SOURCES

Figure 8.3: Spectra and the best-fit power-law models of NIR-unIDed bright (S) Chandra sources (I330–
I345).

The second argument is the HR of NIR-unIDed sources. Figure 8.4 shows the histogramof the HR for NIR-IDed (solid ) and NIR-unIDed (dashed ) Chandra sources. These two
histograms are in clear contrast with each other, where NIR-IDed source histogram peaks at−0.8 < HR < –0.6 and NIR-unIDed source histogram at 0.4 < HR < 0.6. With completely
different profiles, it is natural to consider that NIR-IDed and NIR-unIDed sources havedifferent origins for their X-ray emissions.
The spectra of bright (S) sources show the NH values of ∼1–3×1022 cm−2 (Table 8.1).
When absorbed with this column density, a power-law spectrum of Γ = 1.7 has the HR of
0.40–0.81. This corresponds to the peak of the NIR-unIDed histogram. On the other hand, athin-thermal plasma spectrum with kB T = 0.8 keV and NH = 6.6×1021 cm−2 (representativevalues for the lower-temperature component; see Sect. 9.2) has HR = –0.77, and that withkB T = 3.0 keV and NH = 6.6×1021 cm−2 (representative values for the higher-temperaturecomponent) has HR = 0.02. These account for the NIR-IDed histogram. All these inferthat the histogram of the NIR-unIDed sources is mainly composed of AGNs, while that of
NIR-IDed sources is of YSOs.
To confirm this further, we combined the spectra of the NIR-unIDed sources in thesame HR bin in Figure 8.4 from HR = 0.0–0.2 to 0.8–1.0, and fitted them with a power-law
model. The spectra and the best-fit models are shown in Figure 8.5, while the best-fit values
are in Table 8.2. The indices of the power-law are consistent with Γ = 1.7 with increasing
absorption from softer to harder HRs.
Third, the number of NIR-unIDed X-ray sources is roughly in the same order of the
expected number of background AGNs. Giacconi et al. (2001)[68] derived the log N − log S

8.1. THE NATURE OF NIR-UNIDED X-RAY SOURCES

173

Figure 8.4: Histogram of Chandra hardness ratio separately for NIR-IDed (solid ) and NIR-unIDed (dashed )sources.

Table 8.2: Power-law fittings of combined spectra of
NIR-unIDed Chandra sources

HR
range
0.0–0.2
0.2–0.4
0.4–0.6
0.6–0.8
0.8–1.0

NH a(1022 cm−2 )0.34 (0.14–0.75)
1.19 (0.80–1.72)
2.16 (1.55–3.08)
3.54 (2.07–5.33)
5.17 (0.00–6.57)

Γa1.20 (0.81–1.81)
1.27 (1.00–1.72)
1.49 (1.12–1.81)
1.58 (1.11–2.55)
1.70 (0.15–2.45)

a The lower and upper limit (1 σ) are given in parentheses.

174

CHAPTER 8. NIR-UNIDED X-RAY SOURCES

Figure 8.5: Spectra and the best-fit power-law models of the combined spectra of NIR-unIDed Chandra
sources in the same HR bin from 0.0–0.2 to 0.2–1.0. In the upper panels, the data (pluses) and the best-fit
model (solid steps) are plotted over the energy (keV; horizontal axis) versus normalized spectral intensity(count rate keV−1 ; vertical axis) plane. The response functions of the optics and the detector are convolved
into the model. In the lower panels, the residuals between the background-subtracted data and the best-fit
(i)
(i)
(i)
model are plotted over the energy (keV; horizontal axis) versus χ(i) = (Edata − Emodel⊗ARF ⊗RM F )/∆Edata(vertical axis) plane.

8.1. THE NATURE OF NIR-UNIDED X-RAY SOURCES

175

relation of extragalactic X-ray sources asÃ

S
N (> S) = 1200 ×−15
2 × 10ergs s−1 cm−2

!−1.0

,

(8.2)

where N (> S) is the number of X-ray sources per square degree brighter than S ergs s−1 cm−2in the hard X-ray band (2.0–7.0 keV). In Sect. 5.1, we discussed the completeness limit of our
Chandra observation to be FX ∼ 10−14.5 ergs s−1 cm−2 in 0.5–8.0 keV. Assuming a power-law
spectrum of Γ = 1.7 and NH = 1–3×1022 cm−2 , the expected number of the extragalactic
sources is 74–81.
Finally, the spatial distribution of NIR-unIDed sources (Fig. 6.8 d) is not correlatedwith the 1.3 mm intensity map, but shows a rather uniform distribution. This is in contrast
with protostar and cTTS X-ray sources.

8.1.2

Sources with YSO-like Features

There are, however, some exceptions for the NIR-unIDed X-ray sources to be of the extragalactic origin. Some sources show YSO-like features.
Figure 8.4 shows that there are some soft X-ray sources with HR < 0 among NIRunIDed sources. The overall extinction of our study field is derived to be AK ∼ 0.5–1 mag(Fig. 6.4), which can be converted to NH = 0.5–1×1022 cm−2 using the equation (7.6). With
this absorption, the power-law spectrum of Γ = 1.7 has the HR of 0.12–0.40. Even with noabsorption, the spectrum has the HR of –0.45. Most of the NIR-unIDed X-ray sources with
HR < 0 are unlikely to be AGNs.
Some sources appear to be spatially associated with the 1.3 mm cloud ridge (Fig. 8.6).
If all the NIR-unIDed sources were distributed uniformly in the ACIS-I FOV, the number
density would be ∼0.37 arcmin2 . The expected number of sources within the integral shapeof the 1.3 mm intensity (∼9.7 arcmin2 ) is thus calculated to be ∼3.5. More than twice
numbers of NIR-unIDed sources (I132, I135, I175, I186, I196, I203, I241, I247, and I363) are
actually within the integral shape, indicating that some of them have physical associations
with the cloud cores.

176

CHAPTER 8. NIR-UNIDED X-RAY SOURCES

06:00

I203

I271
I205

-4:59:00
I379

07:00

I132

I255
I199

I260

I100

I224
I186

I95

09:00

I275

02:00
I78
I196
I362
I119
I221

I88

I361

I253

I97

decl. (J2000.0)

01:00
decl. (J2000.0)

08:00

I135

03:00

I98

I175
I188

I285

I266

I133
I363

I235
I273

I163

-5:00:00

I190

I

I115
I380

I366

I359

-5:10:00

11:00

I134

04:00

I160
I86

I376

12:00

I228

05:00

I271

35

I375

I184

I281

I137

13:00

I377

I247 I222
I241

5:35:30

25
5:35:20
R.A. (J2000.0)(a) OMC-3

1535

5:35:30

25

5:35:20

15

R.A. (J2000.0)(b) OMC-2

Figure 8.6: Positions of NIR-unIDed Chandra sources (pluses) with their name over the the 1.3 mm
intensity in gray scale (Chini et al. 1997[35] ). (a) OMC-3 and (b) OMC-2.

8.2. H2 IMAGING OBSERVATIONS ON OMC-3

177

8.2

H2 Imaging Observations on OMC-3

8.2.1

Observation

In order to identify the nature of the NIR-unIDed X-ray sources with YSO-like features, we
further conducted H2 mapping observations of OMC-3 with QUIRC (Fig. 8.7). A global mapof molecular outflows in star-forming regions is quite useful to see the position and distribution of protostars. QUIRC provides a 3.20 ×3.20 FOV with the pixel scale of 0.18900 pixel−1 .
With dithering observations, we took images of three 4.20 ×4.20 regions in two narrow-bands(H2 at 2.12 µm and K-continuum at 2.26 µm). Each FOV was exposed for 60 s on March
13, 2001. The seeing was ∼1.000 .

55:00

A

decl. (J2000.0)-5:00:00

B

C

05:00

-5:10:00

15:00

5:36:00

35:30
R.A. (J2000.0)

5:35:00

Figure 8.7: FOVs of the H2 and K-continuum observations using QUIRC. They are respectively named
region A, B and C. The Chandra ACIS-I FOV is also shown with the large oblique square. The contours are
the 1.3 mm intensity (Chini et al. 1997[35] ).

178

CHAPTER 8. NIR-UNIDED X-RAY SOURCES

8.2.2

Analysis & Results

The images were reduced following the standard procedures using IRAF; dark subtraction,flat fielding, sky subtraction, bad pixel removal for each frame, and correction for ditheringto construct the final images.
The H2 and K-continuum images in three regions were binned with the neighboring 2×2
pixels and smoothed with a Gaussian function to attain better signal-to-noise ratio. The
obtained H2 maps are shown in Figure 8.8. Some Chandra sources (e.g.; I241 and I247) were
found be associated both with 1.3 mm intensity and H2 features.

8.3

NIR Observations on MMS 2 and MMS 3

8.3.1

Observation

As a test case to study the X-ray emission associated with the 1.3 mm cloud core and H2
outflow, we focus on the X-ray sources at MMS 2 and MMS 3. Figure 8.9 gives a close-up
view of MMS 2–MMS 3 region in the hard (3.0–6.0 keV) and soft (0.5–3.0 keV) X-ray band.
These two images were binned with 0.100 pixel−1 and smoothed with a Gaussian functionof 6 bins to attain the sub-pixel resolution, utilizing the dithering observation of Chandra.
We see that I128 is separated into four components; three (I128a, I128b and I128c) are in
the hard and one (I128d) is in the soft band image. Based on the spatial coincidence with
1.3 mm cores and their hard X-ray spectra, Tsuboi et al. (2001)[188] proposed that I128a at
MMS 2 and I132 and MMS 3 are the first candidates of the X-ray-emitting class 0 objects.
Previous observations in the radio and NIR band revealed that there is a molecular
outflow (Aso et al. 2000[11] ; Yu et al. 1997[199] ), an optical jet (Reipurth et al. 1997[161] ) anda radio jet (Reipurth et al. 1999[162] ) originating from MMS 2, which strongly indicates thata protostar or protostars are embedded in this core. However, the spatial resolutions ofthese NIR and radio observations (including our QUIRC observations) are not high enoughto match the Chandra resolution, which makes impossible to discuss the correlation of the
X-ray emissions with the outflow and jet sources. Clearly, follow-up observations with muchhigher spatial resolution, comparable to that of Chandra are needed.
Using IRCS at the Cassegrain focus of the Subaru telescope, we took three broad-band8.3. NIR OBSERVATIONS ON MMS 2 AND MMS 3

179-4:59:00-4:59:00

(B)

(A)

I72

30

30

I55

I163
-5:00:00-5:00:00
I135

30
MMS4
-5:01:00

30
decl. (J2000.0)

decl. (J2000.0)

MMS1

MMS2

MMS3
I132

MMS5
I97

30

MMS6

-5:01:00
I30
30

I49

-5:02:00-5:02:00

I43

I78
30

30

I196
I362
-5:03:00-5:03:00
28

26

24

22 5:35:20

18

16

14

12

R.A. (J2000.0)

08

06

04
02 5:35:00
R.A. (J2000.0)

58

56

I196

(C)

-5:03:00

12 5:35:10

I221
30

MMS7
I160

decl. (J2000.0)-5:04:00
30

I228-5:05:00

MMS8
I184
I137

30

MMS9

I241
I247

-5:06:00

I271

I222

MMS10

I203
I205

30

I235
36

34

32

I363

5:35:30

28

26

24

22

5:35:20

R.A. (J2000.0)

Figure 8.8: QUIRC H2 -band images of three regions in OMC-3. The gray scale gives the H2 intensity with
K-continuum not subtracted, while the contours give the 1.3 mm intensity (Chini et al. 1997[35] ). The crosses
and pluses show the position of NIR-IDed and NIR-unIDed Chandra sources. The names of NIR-unIDed
X-ray sources are given in Roman, while those of 1.3 mm cores are in Italic.

180

CHAPTER 8. NIR-UNIDED X-RAY SOURCES-5:00:10-5:00:10

15

15
MMS1

20

I128b
I128a

I135

30
05351773-0500309

35

MMS2

I128c

40
45

25
I123

30

MMS3

I128d

35
05351773-0500309

40
4505351833-0500329

50

decl. (J2000.0)

decl. (J2000.0)

202505351833-0500329

50

I132

55

55
5:35:20

19

18
R.A. (J2000.0)(a) hard band image

5:35:17

5:35:20

19

18
R.A. (J2000.0)

5:35:17(b) soft band image

Figure 8.9: Close-up images on I128 in MMS 2 for the (a) hard (3.0–6.0 keV) and (b) soft (0.5–3.0 keV)
X-ray band. I128 can be separated into four components; I128a, I128b, and I128c in the hard, and I128d inthe soft band image. The positions of QUIRC sources are given with pluses with the prefix in their names(“TKK J”) omitted. The contours give the 1.3 mm intensity (Chini et al. 1997[35] ).

(J, H, and K -band) and two narrow-band (H2 and K-continuum) images on November 30
and December 4, 2000. The seeing was ∼0.500 on both nights. The J -, K -, H2 -, and Kcontinuum-band images were exposed for 600 s, while the H -band images were for 300 s.
IRCS provides a FOV of 6000 ×6000 with a pixel scale of 0.05800 pixel−1 . With ditheringof five FOVs (Fig. 8.10), we covered a 9000 ×9000 field encompassing both MMS 2 and MMS 3
in the central 3000 ×3000 region. Dithering compensates for the pixel-to-pixel variation inquantum efficiency of the detector and enables to construct the sky image by the mediansky technique without taking a sky frame. In a dithering observation of five FOVs, we have
five ADU values at each pixel of the detector. By leaving the median values among the five,
we can obtain the median-sky image.
As we had no detection in the J band from the two NIR sources at MMS 2, we obtained
an additional L0 -band image of MMS 2 with NSFCam at the Cassegrain focus of IRTF on
December 23, 2000 with the integration time of 216 s. The seeing was ∼1.000 . NSFCamprovides a 3800 ×3800 FOV with the pixel scale of 0.14800 pixel−1 . With dithering, we covereda 6400 ×6400 field.

8.3. NIR OBSERVATIONS ON MMS 2 AND MMS 3

181

Figure 8.10: Configuration of IRCS dithering observations. Five frames (frame numbers are given at thebottom right of each frame) with 6000 ×6000 were combined to construct a 9000 ×9000 image. The hatched region
at the center was covered by all frames. The same configuration with a different dithering amplitude was
employed for QUIRC H2 and NSFCam observations.

8.3.2

Analysis & Results

Source Extraction and Photometry of Broad-band Images
The images were reduced following the standard procedures using IRAF; dark subtraction,flat fielding, sky subtraction, bad pixel removal for each frame, and correction for ditheringto construct a final image (Figs. 8.11 and 8.12).
SExtractor (Bertin & Arnouts 1996[21] ) was used for source extraction and photometry.
Nine sources (IRS 1–IRS 9) were extracted from the K -band image (Table 8.3). For each
K -band detected source, we performed a 1.000 -aperture photometry in the J, H, and K band.
We transformed their magnitudes into the CIT color system in the following way. Seven
sources have the counterpart in the Point Source Catalog of the 2MASS Second Incremental
Data Release. Referring to their J -, H -, and K s -band magnitudes, we derived a linear
relation between IRCS and 2MASS magnitudes in each band. We first converted the IRCS
magnitudes into 2MASS magnitudes using these relations and then into the CIT color systemusing the formulae given in Carpenter (2001)[27] .
For the L0 -band image with NSFCam, we performed a 2.000 -aperture photometry of
IRS 3, IRS 4, and IRS 5. We first calculated the magnitudes with the photometric zero-

182

CHAPTER 8. NIR-UNIDED X-RAY SOURCES(a)
19

5:35:20

R.A. (J2000.0)
18

15

16

17

I121
-5:00:00

IRS1
IRS2

10

MMS1

decl. (J2000.0)

20

I123

I135

30

MMS2

I101

IRS4
IRS7

40

IRS6

MMS3
50 MMS4

I132

01:00

I140
IRS8

I103

10

IRS9
20

(b)

R.A. (J2000.0)
24

17.6

5:35:18.0

18.4

18.8

17.2

26
28

I128b
I123

decl. (J2000.0)-5:00:30
32
34

I128c
IRS4
I128d

36
38

I128a
IRS5

IRS3

40

Figure 8.11: (a) IRCS K -band image with the logarithmic gray scale to stress diffuse features. (b) Close-up
view of the MMS 2 region (shown in a rectangle in a) in the linear scale to show the accurate positions ofpoint sources. The K -band sources (IRS 1–IRS 9) are labeled in Italic, while the positions of the X-ray
sources are with squares with their names in Roman. The contours in (a) are the 1.3 mm intensity. Four
1.3 mm cores (MMS 1–MMS 4) are identified in this region (Chini et al. 1997[35] ). The plus in (b) shows
the position of the 3.6 cm source (Reipurth, Rodrı́guez, & Chini 1999[162] ).

8.3. NIR OBSERVATIONS ON MMS 2 AND MMS 3

183

point of 20.3 mag1 , then converted them into the CIT L-band color using2(K − L)CIT = 0.820 × (K − L0 )IRTF ,(8.3)

where we assumed K CIT = K IRTF as the first order approximation.

-5:00:20

decl. (J2000.0)

25-5:00:30
IRS5
35

IRS4
IRS3

-5:00:40
45-5:00:50
5:35:2019

5:35:18

17

R.A. (J2000.0)

Figure 8.12: NSFCam L0 -band image of MMS 2. The positions of the K -band sources (IRS 3–IRS 5) are
shown with pluses.

Correlation with X-ray Sources
The X-ray counterpart was searched for each NIR source using Table A.1. From the visualinspection of the NIR and X-ray images, we identified the X-ray sources I121, I123, I101,
I140, and I103 to be the counterpart of IRS 1, IRS 4, IRS 6, IRS 8, and IRS 9, respectively.
Two NIR sources (IRS 3 and IRS 5) and four X-ray sources (I128a, I128b, I128c,
and I128d in Fig. 8.9. These respectively correspond to the source 8, 8a, 8b, and 8c in
Tsuboi et al. 2001[188] ) are crowded at MMS 2. In order to find the X-ray counterpart of the
NIR sources, we adjusted the X-ray image by a shift and a rotation so that each X-ray source(I101, I103, I121, I123, and I140) comes closest to its NIR counterpart. After this procedure,
the positional offset between the NIR sources and their X-ray counterparts is ∼0.2500 (1 σ).
1
2

See http://irtf.ifa.hawaii.edu/Facility/nsfcam/hist/backgrounds.html.
See http://irtf.ifa.hawaii.edu/Facility/nsfcam/hist/color.html.

184

CHAPTER 8. NIR-UNIDED X-RAY SOURCES

Then, I128d is found to be the closest source to IRS 5 with the separation of 0.4600 ,hence is the X-ray counterpart of IRS 5. On the other hand, IRS 3 is separated by 0.8100
from the closest X-ray source; I128a. Assuming that the separation between a NIR and
X-ray counterpart pair follows a Gaussian distribution of σ = 0.2500 , the separation between
IRS 3 and I128a is more than 3 σ. We therefore conclude that I128a is not the X-ray emission
from IRS 3. In fact, no separation larger than 0.8100 is found in any other NIR and X-ray
counterpart pairs. I132 at MMS 3, as well as I128a at MMS 2, has no NIR counterpart.
We chose several source-free regions near the positions of I128a and I132 for a 1.000 aperture photometry in order to estimate the background level. We found the K -band
upper limit of I128a and I132 to be ∼19.6 mag at the 3 σ level.

R.A.a(J2000.0)
IRS 1 05:35:17.415
IRS 2 05:35:16.168
IRS 3e 05:35:18.275
IRS 4 05:35:17.736
IRS 5e 05:35:18.340
IRS 6 05:35:15.265
IRS 7 05:35:15.837
IRS 8 05:35:19.980
IRS 9 05:35:15.463

decl.aJb
Hb
Kb
L0b(J2000.0)(mag) (mag) (mag) (mag)−04:59:57.24
17.8
14.7
13.0 . . . . .
−05:00:02.58
17.0
14.1
12.3 . . . . .
−05:00:33.93 >19.6
18.0
13.2
9.17
−05:00:31.07
15.4
13.2
11.7 10.5−05:00:33.01 >19.6
15.8
11.4
7.86
−05:00:33.47
13.3
12.7
12.5 . . . . .
−05:00:36.34
12.3
11.8
11.7 . . . . .
−05:01:02.64 >19.6 >18.8
14.4 . . . . .
−05:01:12.59
14.2
13.6
13.4 . . . . .

2MASScidentification
0535174–045957
0535161–050002
0535183–050033
0535177–050031
0535183–050033
0535152–050033
0535158–050036
0535199–050102
0535154–050112

e Associated with MMS 2.

d Given in parentheses are the nomenclatures in Tsuboi et al. (2001)[188] .

c 2MASS source names with “2MASSI J” omitted for the prefix. IRS 3 and IRS 5 are not resolved in the 2MASS data.

b All magnitudes are in the CIT color system.

a The positions are determined from the IRCS K -band image in the equinox J2000.0.

ID

Table 8.3: IRCS & NSFCam sources

X-raydidentification
I121 (6)............
............
I123 (7)I128d (8c)I101 (2)............
I140 (12)I103 (3)8.3. NIR OBSERVATIONS ON MMS 2 AND MMS 3
185

186

CHAPTER 8. NIR-UNIDED X-RAY SOURCES

Narrow-band Images
The vibrational-rotational transition of v = 1 − 0 S(1) works as an effective coolant of theexcited hydrogen molecules. Therefore, this emission line serves as a powerful tool to searchfor jets from a protostar and the position of its powering source (Bally et al. 1993[15] ; Hodapp& Ladd 1995[88] ). In the continuum-subtracted H2 -band image, we identified a bubble-likefeature originating from MMS 2. A close-up view of this bubble-like emission is shown in
Figure 8.13, where we see the origin of this feature spatially coincides with I128a. No similarfeature was found for I132 at MMS 3.

R.A. (J2000.0)

18.4

5:35:18.0

16.8

17.2

17.6

26
28

decl. (J2000.0)-5:00:30
32

I123

I128d

I128b

I128c
IRS4

34
36

IRS5
I128a

IRS3
38
40

7

8

9

10

11

12

13

14

Figure 8.13: Continuum-subtracted H2 intensity (gray scale). The hard (3.0–6.0 keV) and soft (0.5–
3.0 keV) X-ray intensity are shown with thick and thin contours. The K-continuum image is multiplied by afactor and subtracted from the H2 image, so that the emissions from IRS 3 and IRS 5 cancel out. Without
K-continuum subtraction, however, we confirmed the same bubble-like feature in the H2 image. The scale
bar at the bottom is in the unit of intensity pixel−1 , where the background level (white) is ∼2.5. The
positions of the K -band sources are shown with pluses. The X-ray and NIR sources are labeled in Romanand Italic, respectively.

8.3. NIR OBSERVATIONS ON MMS 2 AND MMS 3

8.3.3

187

Discussion

The Nature of NIR Sources
For the classification of IRCS sources, we used the color-color diagram (Lada & Adams 1992[114] ).
The (J –H )/(H –K ) diagram is given in Figure 8.14 (a). Since IRS 3 and IRS 5 have no detection in the J band, we also give the (H –K )/(K –L) diagram in Figure 8.14 (b).

3
5
5
1
2
4
3
dwarfscTTS locus
giants7 6

4cTTS locus

9

Figure 8.14: (a) (J –H )/(H –K ) color-color diagram and (b) (H –K )/(K –L) color-color diagram. IRS 1–
IRS 9 are plotted in the CIT color system with the label of their names (“IRS” is omitted). The uncertainty isless than roughly ± 0.1 mag for each color. The intrinsic colors of dwarfs and giants are given with thick solid
curves (Tokunaga 2000[185] ), and the cTTS locus is with the thick solid line (Meyer et al. 1997[130] ). Their
extinction vectors are given with the thin solid lines. We assumed the slope of the reddening lines to be E(J−H)reddening /E(H−K)reddening = 1.69 and E(H−K)reddening /E(K−L)reddening = 1.63 (Meyer et al. 1997[130] ).
The AV of each source is estimated from E(H − K)reddening = 0.065 × AV or E(K − L)reddening = 0.04 × AV
(Meyer et al. 1997[130] ).

IRS 3 and IRS 5 are at the center of a millimeter core (MMS 2) and are located ∼1.3400(∼600 AU at the distance of 450 pc) apart from each other (Fig. 8.11). Together with theirlarge extinction of more than AV > 50 mag and large NIR excess seen in Figure 8.14 (b),they are class I protostars probably comprising a binary system.
IRS 1, IRS 2 and IRS 4 are at the reddening region of the cTTS locus with a moderate
extinction of AV ∼ 30 mag (Fig. 8.14 a). They are located at the edge of 1.3 mm cores

188

CHAPTER 8. NIR-UNIDED X-RAY SOURCES(Fig. 8.11), thus are most likely to be cTTSs.
IRS 6, IRS 7, and IRS 9 are located away from the cloud cores (Fig. 8.11) and have lessextinction (Fig. 8.14 a). Among them, IRS 6 and IRS 9 are considered to be wTTSs dueto the association with X-ray emissions. IRS 7, which has no X-ray counterpart, may be aback- or foreground source.
It is hard to infer the nature of IRS 8 from NIR observation alone because it has only
the K -band detection. However, its X-ray counterpart (I140) shows a thermal emission ofkB T = 3.12 keV, LX = 6.32×1030 ergs s−1 , and NH = 6.22×1022 cm−2 (Table 7.1). These are
typical values for class I sources (Table 9.5), hence this source is most likely to be a class I
protostar.

8.4

Centimeter Observations on MMS 2 and MMS 3

8.4.1

Observation

We further took a centimeter image on the MMS 2 region. The purpose of this observation
is to determine the position of the protostellar core with an accuracy of 0.100 and to compare
it with the X-ray image. Protostars are often accompanied by free-free emissions within
100 AU (0.200 at MMS 2), which is detectable mostly as point-like by the centimeter continuum imaging observations (Anglada et al. 1992[7] ; Rodrı́guez, Anglada, & Raga 1995[164] ).
When observed with long-baseline interferometer observations, centimeter imaging is themost accurate method to determine the position of protostars, providing a vital clue todiscuss the mechanism of the X-ray emissions from the youngest phase of protostars.
We conducted our centimeter observation with VLA on February 11, 2002. We used
the A configuration to achieve the highest possible spatial resolution. A 3.6 cm map was
obtained with the integration time of ∼3.5 hours, the band width of 50 MHz, and the phasecenter at R.A. = 05h 35m 18.3s and decl. = –05◦ 000 3300 . The map is sensitive to the structuresmaller than ∼200 with the angular resolution of ∼0.200 . 3C 48 (3.25 Jy) and 0541−056(0.98 Jy) were used as the flux and phase calibrator, respectively.

8.4. CENTIMETER OBSERVATIONS ON MMS 2 AND MMS 3

8.4.2

189

Analysis & Results

Data reduction, calibration and analysis were performed using AIPS3 . The natural weighted
map is shown in Figure 8.15. We detected two sources (VLA 1a and VLA 1b) above the 3 σlevel, for which we derived the position and the flux density (Table 8.4). VLA 1a is slightly
extended, so we also determined the length of the major (minor) axis and position angle to be
0.4000 (0.0900 ) and 32.2 degree, respectively. These two sources were not resolved in the prior
D configuration observation and were named altogether as VLA 1 (Reipurth et al. 1999[162] ).

-05:00:26
28

decl. (J2000.0)

30

VLA 1aIRS5

32
34

VLA 1b

IRS3

36
38
40
05:35:18.8

18.6

18.4

18.2

18.0

17.8

R.A. (J2000.0)

Figure 8.15: The 3.6 cm image of MMS 2 and MMS 3 with VLA. Contours: the 3.6 cm intensity. The
contour levels are 3–9 σ with the step of 3 σ, where the background noise is ∼7.7 µJy beam−1 . The
synthesized beam size is at the bottom left. Pluses: the positions of NIR sources. Arrow : the position angle
of VLA 1a.

3

See http://www.cv.nrao.edu/aips/.

190

CHAPTER 8. NIR-UNIDED X-RAY SOURCES

Table 8.4: VLA sources

ID

R.A.
(J2000.0)
VLA 1a 05:35:18.335
VLA 1b 05:35:18.271

decl.
fluxa
(J2000.0)(µJy)−05:00:32.97
128−05:00:33.93
54

major axis
(00 )
0.40
..........

minor axis
(00 )
0.09
..........

IRCS
counterpart
IRS 5
IRS 3

a The flux density is corrected for the primary beam response.

8.4.3

Discussion

The Nature of Centimeter Sources
For the following reasons, we conclude that both VLA 1a and VLA 1b are free-free emissions
from HII regions ionized by the UV radiation from the shock front produced by the collisionof a protostellar jet upon a dense ISM obstacle (Curiel et al. 1987[42] ).
First, these centimeter sources are considered to be the counterpart of class I protostars(IRS 3 and IRS 5) from their proximity. The embedded protostars are frequently associatedwith centimeter emissions, and detailed studies indicate that most of them, if not all, are offree-free emission origin (Anglada 1996[8] ).
Second, IRS 3 and IRS 5 have the NIR magnitudes and colors of J 0 > 11.3 mag and
J –H > 1.6 mag, and J 0 > 11.3 mag and J –H > 3.8 mag, respectively (Table 8.3). This
indicates that both sources have a mass less than 2 M¯ , which rules out the possibility thatthe centimeter emissions are from HII regions generated by stellar UV photons.
Third, the flux density multiplied by the square of the distance (Sν D2 ) and the momentum rate in the outflow (dP/dt) of VLA 1a and VLA 1b fit well with a known empirical
relation (Anglada et al. 1992[7] ) and theoretical understandings (Curiel et al. 1987[42] ) between these two parameters. Figure 8.16 shows the relation between Sν D2 and dP/dt of
16 embedded objects, where we added VLA 1a/b with Sν D2 = 0.182 × 0.452 mJy kpc2
(Table 8.4) and dP/dt = 3 × 10−5 M¯ yr−1 km s−1 (Table 3.2; Aso et al. 2000[11] ). The
limited spatial resolution of the HCO+ and CO observations could not determine which of
the three 1.3 mm clumps (MMS 2–MMS 4) is responsible for the molecular outflow. However, VLA 1a and VLA 1b in MMS 2 are the only 3.6 cm sources that are associated with
MMS 2–MMS 4 (Reipurth et al. 1999[162] ). We can therefore safely assume that the dP/dt

8.4. CENTIMETER OBSERVATIONS ON MMS 2 AND MMS 3

191

value determined by the molecular outflow represents the sum of the momentum rate from
VLA 1a and VLA 1b. Similarly, we summed the flux density of VLA 1a and VLA 1b for theSν D2 value.
Fourth, in case of VLA 1a, the emission is elongated (the arrow in Fig. 8.15) along thedirection of global outflow seen in the H2 v = 1 − 0 S(1) band (Fig. 8.13), which is characteristic for the free-free centimeter emissions of shock induced plasma (Anglada 1996[8] ).

Figure 8.16: Relation between the flux density multiplied by the square of the distance (Sν D2 ) and theoutflow momentum rate (dP/dt). Open squares are from Anglada et al. (1992)[7] , who derived an empirical
relation among these sources (dashed line). The filled square (VLA 1a/b) is roughly consistent with thisrelation.

192

CHAPTER 8. NIR-UNIDED X-RAY SOURCES

Chapter 9
Discussion
Contents
9.1

9.2

9.3

X-ray Emissions from NIR-IDed Sources: (1) Mass . . . . . . . 194
9.1.1

X-ray Properties among Mass Ranges . . . . . . . . . . . . . . . . 194

9.1.2

High Mass Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . 194

9.1.3

Intermediate Mass to Very Low Mass Sources . . . . . . . . . . . . 196

X-ray Emissions from NIR-IDed Sources: (2) Plasma Temperature201
9.2.1

Two-temperature Plasma Emissions . . . . . . . . . . . . . . . . . 201

9.2.2

Origins of Two-temperature Plasma . . . . . . . . . . . . . . . . . 203

9.2.3

X-ray Properties among Evolutional Classes . . . . . . . . . . . . . 206

X-ray Emissions from NIR-unIDed Sources . . . . . . . . . . . . 208
9.3.1

Jet-induced Plasma Emissions

9.3.2

Magnetic Activities of Deeply Embedded YSOs . . . . . . . . . . . 213

193. . . . . . . . . . . . . . . . . . . . 208

194

CHAPTER 9. DISCUSSION

In this chapter, we discuss the X-ray emission mechanisms of X-ray sources based on
their multi-wavelength features described in the previous chapters. The first two sections
are for NIR-IDed X-ray sources. In Sect. 9.1, we compare the X-ray properties in different
mass ranges (Sect. 9.1) and discuss that the IM, LM, and VLM sources have the same Xray emission mechanisms in contrast to HM sources. In Sect. 9.2, we describe that their
X-ray emissions consist of two components of different temperatures and propose that thehard component originates from flares while the soft component is from stellar coronae. In
Sect. 9.3, we deal with NIR-unIDed X-ray sources, and interpret their X-ray emission in thecontext of jet-induced plasma and the magnetic activities of deeply embedded NIR invisible
YSOs.

9.1

X-ray Emissions from NIR-IDed Sources: (1) Mass

9.1.1

X-ray Properties among Mass Ranges

Based on the mass estimates of NIR-IDed X-ray sources using the J /(J –H ) color-magnitude
diagram, we separated them into four mass ranges (HM, IM, LM, and VLM) in Sect. 6.2.
The NIR sources in the ACIS-I FOV are separated in the same manner in order to calculate
the X-ray detection rate of each mass range. Readers should note that NIR sources classified
as LM and VLM are contaminated by back- or foreground sources (Sect. 6.1), which gives
the lower limit of the X-ray detection rate of these groups. The number of NIR and X-ray
sources and the detection rate are summarized in Table 9.1 along with the results of the
X-ray temporal and spectral analyses. The averaged X-ray properties are in Table 9.2.

9.1.2

High Mass Sources

We have one HM source in our sample. The source; ν Ori has the spectral type of B1 V
(Kukarkin et al. 1971[111] ), the mass of 101.05 M¯ and the bolometric luminosity of 104.06 L¯(Greenstein 1998[71] ). The X-ray counterpart (I242) shows a stable light curve with a soft
spectrum. This source is faint (T) and faint (S), so no temporal and spectral analyses were
performed (Sects. 7.1 and 7.2). In order to compare with sources in other mass ranges, we
examined the temporal variation of I242 and found that the constant flux model was not
rejected with α > 0.05 (Fig. 9.1). We also fitted the spectrum in the range of 0.5–2.0 keV

9.1. X-RAY EMISSIONS FROM NIR-IDED SOURCES: (1) MASS

195

Table 9.1: Number of sources among mass ranges

HM
NIR sources . . . . . . . . . . . . . . . . . . . .
X-ray sources . . . . . . . . . . . . . . . . .
NIR sources with NIR excess . .
X-ray sources with NIR excess
bright (T) . . . . . . . . . . . . . . . . . . . . . .
variable . . . . . . . . . . . . . . . . . . . . . . .
bright (S) . . . . . . . . . . . . . . . . . . . . . .
one-temperature . . . . . . . . . . . . . .
two-temperature . . . . . . . . . . . . . .

1
1(100%)
0
0
(N/A)
1
0
(0%)
0
0
(N/A)
0
(N/A)

IM
26
21
(81%)
12
11
(92%)
16
12
(75%)
18
10
(56%)
8
(44%)

LM
210
139
(66%)
45
31
(69%)
78
42
(54%)
94
57
(61%)
27
(29%)

VLM
462
107
(23%)
74
11
(15%)
18
7
(39%)
22
13
(59%)
6
(27%)

sum
699
268
(38%)
131
53
(40%)
113
66
(58%)
134
80
(60%)
41
(31%)

Table 9.2: Comparison of X-ray properties among mass ranges

HMa< log NH (cm−2 ) > . . . . . . 21.5
< kT (1) (keV) > . . . . . . . . . 0.64
(1)
< log LX (ergs s−1 ) > . . . 30.3
(2)
< kThigh (keV) > . . . . . . . . N/A(2)< log LX high (ergs s−1 ) > N/A(2)< kTlow (keV) > . . . . . . . . . N/A(2)< log LX low (ergs s−1 ) > N/A

IM
21.9±0.4
3.85±1.630.5±0.4
4.00±2.1
30.6±0.7
0.89±0.230.5±0.5

a The result of the spectral fitting of I242 is shown.

LM
21.6±0.72.30±2.030.1±0.52.75±1.230.3±0.4
0.77±0.3
30.1±0.5

VLM
21.7±0.6
2.04±2.329.8±0.4
2.41±1.1
29.7±0.2
0.44±0.3
29.9±0.7

196

CHAPTER 9. DISCUSSION

to avoid background contamination in the hard X-ray band to have an acceptable fit witha thin-thermal plasma mode. The best-fit parameters are given in Table 9.3, while thespectrum and the best-fit model are in Figure 9.1.
The X-ray emissions from earlier-type main sequence stars than B2 are explained by
the stellar wind model (Lucy & White 1980[118] ; Lucy 1982[119] ), in which the strong stellar
wind propagating through the ambient matter at the speed of ∼1000 km s−1 ionizes the gas
with shocks.
The past X-ray observations on this class of stars revealed that they show non-variable
light curves, softer spectra than kB T ∼ 1 keV, and LX /Lbol = 10−7.1 –10−7.6 (Berghöfer et al.
1997[20] ; Feigelson et al. 2002[54] ). The X-ray features of I242 follow very well with that of
the typical early-type stars with kB T = 0.64, LX /Lbol = 10−7.3 , and an non-variable light
curve. We conclude that I242 is a high-mass main sequence source and the X-ray emission
from it is of stellar wind origin.
Table 9.3: One-temperature plasma fittings of the high mass source

ID
I242

countsa S/N b
660

NH c
kB T c(1022 cm−2 )(keV)
8.54 0.34 (0.25–0.39) 0.64 (0.58–0.69)

LX a(ergs s−1 )2.14e+30

a Values in the 0.5–8.0 keV range.
b Values in the 2.0–8.0 keV range.
c The lower and upper limit (1 σ) are given in parentheses.

9.1.3

Intermediate Mass to Very Low Mass Sources

Previous X-ray observations mainly focused on the X-ray emissions from LM YSOs, revealingthat they are of thin-thermal plasma origin generated and maintained by magnetic activities
on the stellar surface. They show hard and strong X-ray emissions of kB T = 0.5–2.0 keV andLX /Lbol = 10−2 –10−5 with occasional flare-like variability (Feigelson & Montmerle 1999[53] ).
Less is known for higher mass YSOs because they have lower population and evolve more
quickly, making these samples fewer and more distant. The X-ray emissions from VLM
sources are also behind our understandings on LM YSOs because they are fainter. Using
our VLM, LM, and IM samples, we discuss that YSOs in these mass ranges have the same
X-ray emission mechanism.

9.1. X-RAY EMISSIONS FROM NIR-IDED SOURCES: (1) MASS

197

Figure 9.1: (left) Light curve of the high mass source (I242) over the count rate (s−1 ; vertical axis) versus
the time from the start of the observation (s; horizontal axis) plane. (right) Spectra and the best-fit models of
one-temperature thin-thermal plasma fittings of the high mass source (I242). The metallicity of all elements
is fixed to be 0.3 solar. In the upper panel, the data (pluses) and the best-fit model (solid steps) are plotted
over the energy (keV; horizontal axis) versus normalized spectral intensity (count rate keV−1 ; vertical axis)
plane. The response functions of the optics and the detector are convolved into the model. In the lower
panel, the residuals between the background-subtracted data and the best-fit model are plotted over the
(i)
(i)
(i)
energy (keV; horizontal axis) versus χ(i) = (Edata − Emodel⊗ARF ⊗RM F )/∆Edata (vertical axis) plane.

First, we rule out the possibility that the X-ray emissions from IM YSOs are from their
LM companion, which is the most favored scenario for the X-ray emissions from IM main
sequence stars (Berghöfer & Schmitt 1994[20] ). This is because IM main sequence stars haveno mechanism to generate high temperature plasma. We compared the X-ray detection rateof our IM samples with the binary rate of the Orion and found that the former (∼80%)
is much higher than the latter (∼15%). The binary rate is presented by Padgett et al(1997)[146] , who derived the value based on the Hubble Space Telescope observations on three
Orion stellar clusters (NGC 2024, NGC 2068, and NGC 2071). They examined 99 sources
down to I < 19 mag and found that 15 of them have a binary companion in the separation
range of 0.300 < θ < 2.300 (∼100–1000 AU). As this rate gives the upper limit of IM sources
to have a LM binary, all of the X-ray emissions from our IM sources can not be attributable
to their companion sources.
We can confine our IM samples to those robustly in the pre-main-sequence stage by
picking up sources with the NIR excess (the remainders are the mixture of main and premain sequence sources). All but one IM sources with NIR excess are found to have X-ray
detections, indicating that virtually all IM YSOs emit X-rays.
We have three lines of evidence to conclude that the same X-ray emission mechanism
functions for VLM, LM, and IM YSOs. First, all VLM–IM sources in our sample show

198

CHAPTER 9. DISCUSSION

similar X-ray features when averaged over the group (Table 9.2). About ∼60% of themshow one-temperature plasma spectra of 2–3 keV and ∼30% show two-temperature plasma
with the combination of ∼1.0 keV and 2–3 keV. This is in contrast to the HM source (I242),
which only shows low-temperature (∼0.5 keV) plasma spectrum.
Second, the ratio of the X-ray and bolometric luminosity (LX /Lbol ) of most of thesesources is in the range of 10−2 –10−5 (Fig. 9.2). The value is consistent with the previous
observational results on LM YSOs (Feigelson & Montmerle 1999[53] ) and higher than thatof the typical HM main sequence stars with stellar wind origin (∼ 10−7 ). In fact, the only
HM (and some IM) source has LX /Lbol ∼ 10−7 . The trend of lower LX /Lbol values towardhigher mass sources (Fig. 9.2) is due to the observational bias. We are dealing with the Xray-selected samples, which causes lower mass (smaller bolometric luminosity) sources not
to be detected even with the same LX /Lbol value. The bias is illustrated with the dashedcurve representing the typical X-ray detection limit of 1029 ergs s−1 (Sect. 5.1).
Third, the LX values of VLM–IM sources increase toward the higher mass sources(Fig. 9.3). An empirical relation between these two parameters was presented by Preibisch,& Zinnecker (2002)[156] for VLM–LM YSOs in a low-mass star forming region (IC 348). We
see that the relation can be extrapolated to apply for IM and VLM sources.
All these arguments infer that VLM–IM sources (including young brown dwarfs) areemitting X-rays with the same mechanism and the level of activity can be scaled with theirmass.

9.1. X-RAY EMISSIONS FROM NIR-IDED SOURCES: (1) MASS

199

Figure 9.2: Relation between the mass (M ) and the ratio of the X-ray (0.5–8.0 keV) and bolometricluminosity (LX /Lbol ) of NIR-IDed X-ray sources. Filled squares are with the X-ray luminosity derived fromthe spectral fittings, while open squares are with the LX values estimated from their X-ray counts using theequation (7.8). The dashed curve shows the typical detection limit of LX = 1029 ergs s−1 .

200

CHAPTER 9. DISCUSSION

Figure 9.3: Relation between the mass (M ) and the X-ray luminosity (LX ) of NIR-IDed X-ray sources in
the 0.5–8.0 keV. Filled squares are with the luminosity derived from the spectral fittings, while open squares
are with the LX values estimated from their X-ray counts using the equation (7.8).

9.2. X-RAY EMISSIONS FROM NIR-IDED SOURCES: (2) PLASMA TEMPERATURE201

9.2

X-ray Emissions from NIR-IDed Sources: (2) Plasma
Temperature

9.2.1

Two-temperature Plasma Emissions

The previous discussion that the same X-ray emission mechanism works for VLM–IM sources
justifies us to deal with them collectively. We consider, for the following reasons, that thesesources have the combination of two X-ray emission mechanisms of different temperature.
Figure 9.4 (a) shows the histogram of the plasma temperatures of VLM–IM sources,
where we count the sources with two-temperature plasma twice at each temperature. We
can see two peaks at kB T ∼ 1 keV and 2–3 keV. According to the standard magnetic
reconnection model of solar flares, the plasma temperature at a flare (Tf ) is described as afunction of the pre-flare density (n0 ), the loop length (L), and the magnetic field strength(B); e.g.,µ¶ 67 µ¶− 1 µ
¶ 27
7
B
n0
L
7
Tf = 2 × 10
(9.1)
[K]
0.003 T
10−15 m−3
107 m
(Yokoyama & Shibata 1998[197] ). Taking into account that these parameters can change
continuously, this histogram should appear with one peak with broad tails. It is more naturalto understand, therefore, that these sources have two different X-ray emission mechanisms,
each of which high and low temperature plasma are attributable to.
This is reinforced by examining sources with two-temperature plasma. Figure 9.4 (c)shows the histogram of plasma temperatures separately for the lower (solid ) and higher(dashed ) temperature component. The peak of the lower temperature component is at kB T
∼ 1 keV, while that of the higher temperature component is at kB T = 2–3 keV. These twocomponents coexist at flare and quiescent phases, because for the reason that the time-sliced
spectra of some brightest sources require a two-temperature plasma model in both phases(Sect. 7.2). It is not the case, therefore, that these X-ray emissions are attributable to only
one component that shows a higher temperature at flare phases and a lower temperature atquiescent phases.
It is also unlikely that the sources with two-temperature plasma are binaries. First,
we confirmed both in the X-ray and the K -band images that only four (I42, I211, I256,
and I314) among the 41 two-temperature sources can be contaminated with their closecompanion. Second, among the 30 bright (S) sources with more counts than 1000 (sources

202

CHAPTER 9. DISCUSSION

Figure 9.4: Histograms of plasma temperatures of bright (S) NIR-IDed X-ray sources; (a) total, (b) onetemperature plasma, and (c) two-temperature plasma sources. In (c), the histograms of the lower and higher
temperature are given with solid and dashed, respectively.

9.2. X-RAY EMISSIONS FROM NIR-IDED SOURCES: (2) PLASMA TEMPERATURE203
with the spectrum of sufficient statistics to examine the two-temperature nature), 23 sources
require two-temperature plasma models (Fig. 7.7). The rate of 77% is much higher than thebinary rate (∼15%) of this region (Padgett, Strom, & Ghez 1997[146] ). Finally, we have noreason to expect that the temperature of each binary component is always the combinationof kB T ∼ 1 keV and 2–3 keV.
One-temperature sources are considered to be with no or negligible contribution byeither component. The two peak profile of their temperature histogram (Fig. 9.4 b) is
consistent with this idea.
The two components show different temporal behavior. In Table 7.5, we see that the EM
values of the high temperature component increase during flare phases, while those of the
low temperature component stay constant or slightly decrease. This indicates that the flarelike variability is caused by the high temperature component. This is further strengthenedby the fact that almost all the one-temperature plasma sources with flare-like variations(Figs. 7.2–7.6) have the plasma temperature of 2–3 keV or higher; e.g., I67 (2.7 keV), I131
(3.2 keV), I138 (7.5 keV), I165 (4.8 keV), I218 (3.1 keV), I264 (5.5 keV), and I280 (2.7 keV).
In contrast, the light curves of the low temperature component show moderate variabilityof no flare-like episodes. Typical examples are the light curves of I54 (0.8 keV) and I282
(1.0 keV).

9.2.2

Origins of Two-temperature Plasma

A similar bimodal structure in the plasma temperature distribution is seen in the sun.
Peres et al. (2000)[150] integrated all the X-ray emissions from the sun using the Soft Xray Telescope (SXT) on Yohkoh and convolved the spectrum with the response function of
ASCA/SIS in order to facilitate direct comparison with the X-ray emissions from other stars.
The synthesized solar spectrum is well fitted with one- or two-temperature plasma modelat the solar minimum and maximum. At the solar maximum, the plasma temperatures are
kB T ∼ 0.2 keV and ∼ 0.5 keV. From the geometrically well-defined data on solar X-ray emissions, the higher and lower temperature components are found to originate from the solar
coronae and flares. We interpret the two-temperature plasma of YSOs in the same analog;
i.e., the higher temperature (2–3 keV) component is from flares and the lower temperaturecomponent is from the coronae.
Two pieces of evidence support our idea. First, similar bimodal temperature structures

204

CHAPTER 9. DISCUSSION

are also seen in other stars, with increasing plasma temperature toward younger samples(Figs. 2.7 and 9.5). Figure 9.6 shows the evolution of the representative plasma temperatures
separately for the higher (filled squares) and lower (and middle) temperature component(open squares). Three G-type main sequence sources (EK Dra, HN Peg, and κ1 Cet; Güdel,Guinan, & Skinner 1997[74] ) and one G-type pre-main-sequence source (SU Aur; Skinner& Walter 1998[173] ) are plotted. As the stellar rotation becomes slower as increasing ages,
main sequence sources evolve magnetically inactive and the plasma temperature decreases(Güdel et al. 1997[74] ). Our sample sources are at the age of ∼1 Myr (or younger), which
settles both of their typical high and low temperatures on this temperature-age relations.

Figure 9.5: Differential emission measure distributions of coronally active main sequence stars(Güdel et al. 1997[74] ); EK Dra (top), HN Peg (middle), and κ1 Cet (bottom).

9.2. X-RAY EMISSIONS FROM NIR-IDED SOURCES: (2) PLASMA TEMPERATURE205

Figure 9.6: Evolution of the plasma temperatures of the soft (and middle) component (open squares) andthe hard component (filled squares) of some main and pre-main-sequence stars (sun; Peres et al. 2000[150] ,EK Dra, HN Peg, and κ1 Cet; Güdel, Guinan, & Skinner 1997[74] , and SU Aur; Skinner & Walter 1998[173] ).

206

CHAPTER 9. DISCUSSION

Second, the time-sliced spectroscopy on our bright X-ray sources (Sect. 7.2) indicatesthat flaring activities are attributable to the high temperature component. This is the samewith the solar plasma and main sequence stars (Güdel et al. 1997[74] ; Güdel et al. 2002[75] ).
The high-temperature plasma component seen in the spectra at quiescent phases may
be the integration of small and temporally-unresolved flares. Güdel et al. (1997)[74] andGüdel et al. (2002)[75] further discussed, based on this interpretation, that the the EM ratioof both components can be a function of flare frequency. Future long-exposure observations
on YSOs as well as main sequence stars will give an insight on this issue.

9.2.3

X-ray Properties among Evolutional Classes

Based on the evolutional class estimates of NIR-IDed X-ray sources using the (J –H )/(H –K ) color-color diagram as well as the U V excess and Hα emission data, we separated theminto class I (protostars), class II (cTTSs), and class III (wTTSs) objects (Sect. 6.2). The
statistics of each class are summarized in Table 9.4 with the results of X-ray temporal andspectral analyses, while the averaged X-ray properties are in Table 9.5.
Table 9.4: Number of sources among classes

X-ray sources. . .
bright (T) . . . . . .
variable . . . . . . . .
bright (S) . . . . . .
one-temperature
two-temperatureclass I class II
13
59
4
31
3
18
(75%) (58%)
7
37
6
25
(86%) (68%)0
10(0%) (27%)

class III othersa sum
170
36
278
71
14
120
38
7
66
(54%) (50%) (55%)
81
17
142
43
13
87
(53%) (76%) (61%)29241(36%) (12%) (29%)

a NIR-IDed but not classified either into class I, II, or III based on their NIR colors.

Despite that we do not have class I objects of two-temperature plasma, we can regard(2)that the < kT (1) > value represents < kThigh > in this class. This is because class I
objects, even if they have two-temperature emissions, appear only with higher temperature9.2. X-RAY EMISSIONS FROM NIR-IDED SOURCES: (2) PLASMA TEMPERATURE207

Table 9.5: Comparison of X-ray properties among classes

class I< log NH (cm ) > . . . . . . 22.6 (±0.3)< kT (1) (keV) > . . . . . . . . . 3.71 (±1.9)< kT (1) (keV) >w a. . . . . . . 3.30 (±1.1)(1)< log LX (ergs s−1 ) > . . . 30.6 (±0.5)(2)< kThigh (keV) > . . . . . . . .
N/A
(2)
a
< kThigh (keV) >w . . . . . . .
N/A(2)< log LX high (ergs s−1 ) >N/A(2)< kTlow (keV) > . . . . . . . . .
N/A
(2)
a
< kTlow (keV) >w . . . . . . .
N/A(2)< log LX low (ergs s−1 ) >N/A−2class II
21.8 (±0.7)2.82 (±1.9)1.85 (±1.0)30.3 (±0.4)3.60 (±2.1)
2.33 (±0.5)30.4 (±0.3)
0.83 (±0.1)
0.85 (±0.1)
30.2 (±0.3)

class III21.5 (±0.6)
2.00 (±1.7)1.32 (±0.4)
30.0 (±0.5)2.64 (±1.2)2.30 (±0.8)30.2 (±0.6)
0.71 (±0.3)
0.88 (±0.2)
30.1 (±0.6)

a Weighted means, which were calculated by weighting the values with the inverse square of

their uncertainty.

plasma due to the heavier extinction at the soft X-ray band. A notable fact is that the(2)(2)< kThigh > decreases along the evolution. A similar trend is seen in < kT (1) > and < kTlow >,although we have to pay attention to the fact that X-ray detections from younger and more
obscured sources are biased for the harder emissions. This trend of decreasing higher plasma
temperature can be understood by extrapolating the relation in Figure 9.6 toward younger
ages than 1 Myr.

208

9.3

CHAPTER 9. DISCUSSION

X-ray Emissions from NIR-unIDed Sources

Ten NIR-unIDed X-ray sources (I128a, I132, I135, I175, I186, I196, I203, I241, I247, andI363) in the 1.3 mm integral-shaped ridge appear to be separated into two groups. The firstgroup consists of four sources (I128a, I175, I241, and I247), which are associated with jet
and outflow systems. The remaining sources comprise the second group, which has no suchfeatures. We try to interpret the X-ray emissions from these two groups in the context of
jet-induced plasma and magnetic activities of deeply embedded NIR invisible YSOs.

9.3.1

Jet-induced Plasma Emissions

Sources in the first group share many characteristics in common (Table 9.6). They are(1) located at the 1.3 mm cloud cores, and (2) are associated with H2 outflows seen in the
QUIRC H2 -band image (Fig. 9.7), (3) CO and HCO+ outflows (Aso et al. 2000[11] ), and(4) the centimeter emissions (Reipurth et al. 1999[162] ). VLA 7 is extended in the directionof molecular outflows, indicating that this is a free-free emission from the HII region ionizedby protostar jets. We resolved VLA 1 into two sources (VLA 1a and VLA 1b) and discussed
that these sources have free-free emissions in origin as well (Sect. 8.4).
Their close-up view in the QUIRC K -band image (Fig. 9.7) reveals more of their common
features. (5) The 1.3 mm cores that contain these X-ray sources also possess a NIR sourcethat is classified either into class I protostars or cTTSs. For TKK J05351833−0500329
at MMS 2, we resolved it into two NIR sources (IRS 3 and IRS 5) with our Subaru and
IRTF observations, and classified them into class I protostars using their J -, H -, K -, andL0 -band colors (Sect. 8.3). TKK J05352333−0507096 at FIR 1c has the color (J –H )CIT =2.83 and (H –K )CIT = 2.19, showing its class I nature (Fig. 6.2). 2MASSI J0535315−050547
at MMS 10, although it shows no NIR excess in the (J –H )/(H –K ) diagram (Fig. 6.2),
have a large extinction with (J –H )CIT = 2.00 and (H –K )CIT = 1.42. Considering its large
extinction and the insensitivity of the K band to the NIR excess emissions, this source canalso be a class I protostar. (6) These NIR sources show apparent reflection features in the
K -band image. Finally, (7) the X-ray sources are close to but significantly offset from these
NIR protostars in the direction of jet and outflow system.

22

I135

I128a

15

22

I135

I128a

50

40

30

15

R.A. (J2000.0)

31 5:35:30 29

28

35

22

34

33

I241

15

31 5:35:30 29

28

2MASSI J0535315-050547

R.A. (J2000.0)

32

I247

I244

16

I128a

21 5:35:20 19
18
17
R.A. (J2000.0)

I135

Figure 9.7: X-ray and NIR images of I128a at MMS 2 (top), I175 at FIR 1c (middle), and I241 and I247 at MMS 10 (bottom). The panelsin the left column are the X-ray images in the hard band, while those in the middle column are the K -band images. The H2 intensity images
are in the right column. I175 was out of the FOV of our H2 observations. The positions of X-ray and NIR sources are marked with pluses
and crosses, respectively.

32
31 5:35:30 29
R.A. (J2000.0)

32

50

40

30

20

10

30
33

2MASSI J0535315-050547

21 5:35:20

20

I247

I244

I241

24
23
22
R.A. (J2000.0)

30
34

25

30
35

26

10

28

27

20

50

40

30

20

10

50

10

I244

21 5:35:20

TKK J05352333-0507096

20

I247

I241

24
23
22
R.A. (J2000.0)

I175

10

33

25

40

30

20

10

16

-5:06:00

34

26

TKK J05352333-0507096-5:07:00

50

40

30

21 5:35:20 19
18
17
R.A. (J2000.0)-5:06:00

35

27

I175

16

decl. (J2000.0)-5:06:00

50

40

30

20

10

50

40

30

20

10

-5:07:00

decl. (J2000.0)

decl. (J2000.0)

decl. (J2000.0)
decl. (J2000.0)

21 5:35:20 19
18
17
R.A. (J2000.0)

10

10

50

40

10

TKK J05351833-0500329

30

20

01:00

decl. (J2000.0)
01:00

50

40

30

decl. (J2000.0)

01:00

50

40

30

20

10

20

10

50

10

50
-5:00:00

50-5:00:00

decl. (J2000.0)-5:00:00

9.3. X-RAY EMISSIONS FROM NIR-UNIDED SOURCES
209

210

CHAPTER 9. DISCUSSION

Table 9.6: NIR-unIDed X-ray sources associated with jet and outflow systems

ID
I128a
I175
I241
I247

X-rayacounts66
33
22
33

1.3 mmjet/outflow associationsbcore
H2 c COd H13 CO+d 3.6 cme
MMS 2
yes yesyes
VLA 1
FIR 1cN/A yesyes
VLA 7
MMS 10 yes yesyes......
MMS 10 yes yesyes......

class I protostarf
TKK J05351833−0500329
TKK J05352333−0507096
2MASSI J0535315−050547
2MASSI J0535315−050547

a Values in the 0.5–8.0 keV range.
b Chini et al. (1997)[35] .
c The H emissions found in QUIRC images (Fig. 8.8). I175 was out of the FOV of our observation.
2d Aso et al. (2000)[11] .
e Reipurth et al. (1999)[162] .

VLA 7 has an extended structure. VLA 1 was resolved into VLA 1a and VLA 1b in
our higher resolution VLA observation (Sect. 8.4), in which we found VLA 1a is also extended in the direction of themolecular outflow as well as VLA 7.

f

The class I protostars located in the same 1.3 mm cloud.TKK J05351833−0500329 was resolved into two class I protostars (IRS 3 and IRS 5) in our higher resolution Subaru observation (Sect. 8.3). I244 is the X-ray counterpart of
2MASSI J0535315−050547.

We pick up I128a as a test case. We revealed the vicinity of this source with our follow-up
studies with high resolution NIR and centimeter imaging observations as follows (Figs. 8.13
and 9.8). Two NIR sources of class I protostar nature (IRS 3 and IRS 5) are located at thecenter of 1.3 mm cloud core (MMS 2). These two protostars accompany centimeter emissions(VLA 1a and VLA 1b) that originate from the the HII region ionized by the protostellar jetsfrom the two NIR sources. A global outflow is seen in the H2 band, the direction of whichaligns with the extended structure of VLA 1a (Sect. 8.3 and 8.4). A hard X-ray source(I128a) is located at the origin of this outflow and has a significant offset from these two
protostars. The X-ray characteristics that we obtained on I128 can be applied to I128a,
because I128a occupies most (∼70%) of the X-ray photons of this complex (Fig. 8.9). It
has a thin-thermal plasma spectrum of kB T = 3.05 keV and EM = 2.1×1053 cm−3 with theabsorption of NH = 1.27×1023 cm−2 (Sect. 7.2).
We propose an interpretation to explain these hard X-ray emissions together with thecentimeter emissions based on the shock-induced plasma scenario. Figure 9.9 shows theschematic view, where the jet from a protostar collides into a dense obstacle and produces
the shock front. The hard X-ray is emitted from the post shock (PS) region, while thecentimeter emission is from the recombination zone (RZ) behind the shock. The RZ ismaintained by the continuous ionization by UV photons from the PS region.

9.3. X-RAY EMISSIONS FROM NIR-UNIDED SOURCES

211

R.A. (J2000.0)
18.4

16.8

17.2

17.6

5:35:18.0

26
28
VLA 1adecl. (J2000.0)-5:00:30
32
34
36
VLA 1b

38

I128a

40

7

8

9

10

11

12

13

14

Figure 9.8: Multi-wavelength view on MMS 2. The H2 intensity is in gray scale, the hard and soft X-rays
are with the thin and the thick contours, and the position of centimeter sources (VLA 1a and VLA 1b) aremarked with pluses. I128a, the hard X-ray peak, is significantly offset from two centimeter emissions in the
direction of global H2 outflow. See also Figure 8.13 for the positions of NIR sources.

Recombination Zone

Post Shock Region
TPS : tempearature
VPS : volume

TRZ : temperature
ARZ : area

shock front
UVvsprotostar

obstacleno : density

cm

X-ray

Figure 9.9: Schematic view of the X-ray and centimeter emissions of protostellar jet origin.

212

CHAPTER 9. DISCUSSIONIn PS, the temperature (TPS ) and the density (nPS ) are expressed as (Raga et al. 2002[158] )µ5

TPS = 1.5 × 10

vs100 km s−1

¶2

[K],

(9.2)

nPS = 4n0 [cm−3 ],(9.3)

where vs and n0 are the velocity and density of the shock produced by the collision of thejet upon the obstacle. Assuming that light elements are fully ionized in PS, the emission
measure (EM ) is given with the electron density (nPS ) and the volume (VPS ) as
EM = n2PS VPS [cm−3 ].

(9.4)

By substituting the observed values (TPS = 35 MK and EM = 2.1×1053 cm−3 ), we obtained
vs = 1.5×103 km s−1 and n0 = 5.3×102 cm−3 . Here, we assumed that PS is a cube with thelength of 0.500 (=the scale of an ACIS-I pixel).
The values of vs and n0 are consistent with what can be independently derived from thecentimeter observations. In RZ, the centimeter intensity (Sν ) is given by
µ ¶2

ARZ
ν
Sν = 2 2kB TRZ
D
c

τν

(9.5)

at the optically-thin limit and with the Rayleigh-Jeans approximation. Here, D is the
distance to the source, and TRZ and ARZ are the temperature and the surface area of RZ.
Curiel et al. (1989)[43] showed that the optical depth (τν ) is expressed in terms of the shock
parameters byµ−7τν = 1.55 × 10

n0
1 cm−3¶µvs
100 km s−1¶1.68 µTRZ
104 K¶−0.55 µ

ν
5 GHz

¶−2.1

.

(9.6)

By substituting the observed values of VLA 1a (ν = 8.3 GHz, Sν = 0.128 mJy, and D =450 pc) as a typical value, we obtainedµn0
1 cm−3¶µvs
100 km s−1¶1.68= 1.7 × 105 .

(9.7)

Here, we assumed that TRZ = 104 K and ARZ is an ellipse of the observed major and minor
axis lengths of VLA 1a.
From the X-ray observation, we can independently derive thatµn0
1 cm−3¶µvs
100 km s−1¶1.68= 5.2 × 104 .

(9.8)

9.3. X-RAY EMISSIONS FROM NIR-UNIDED SOURCES

213

This is in good agreement with the value obtained with the centimeter data in a factor ofa few, supporting the protostellar jet scenario for the origin of the X-ray and centimeteremissions.
Other three X-ray emissions with the same multi-wavelength features can be understoodwith the same scheme. The positions of X-ray and NIR sources are similar to the case of
I128a, where X-ray emissions are 100 –600 offset from the protostar in the direction of jet andoutflow. More interestingly, I241 and I247 are positioned at the opposite side of the central
NIR source (Fig. 9.7). We may be seeing a jet and counter-jet pair of this system. The
combined spectrum of I241 and I247 (Fig. 9.10 a; Table 9.7) supports this idea, which are
well fitted by a thin-thermal plasma model with similar best-fit values (kB T = 2.8 keV,
EM = 9.2×1022 , and NH = 5.8×1022 cm−2 ) with I128a. Likewise, I135 at MMS 2 may be
the counter-jet of I128a (Fig. 9.7).

(a)

(b)

(c)

Figure 9.10: Spectra and the best-fit models of one-temperature thin-thermal plasma fittings of (a)I241+I247, (b) I186, and (c) I132+I135+I196+I203+I363. The metallicity of all elements is fixed to be
0.3 solar. In the upper panels, the data (pluses) and the best-fit model (solid steps) are plotted over theenergy (keV; horizontal axis) versus normalized spectral intensity (count rate keV−1 ; vertical axis) plane.
The response functions of the optics and the detector are convolved into the model. In the lower panels, theresiduals between the background-subtracted data and the best-fit model are plotted over the energy (keV;
(i)
(i)
(i)
horizontal axis) versus χ(i) = (Edata − Emodel⊗ARF ⊗RM F )/∆Edata (vertical axis) plane.

9.3.2

Magnetic Activities of Deeply Embedded YSOs

Other X-ray sources (I132, I135, I186, I196, I203, and I363) that are associated with 1.3 mm
emissions but not with jet and outflow systems can be deeply embedded YSOs such as class 0

214

CHAPTER 9. DISCUSSION

Table 9.7: One-temperature plasma fittings of NIR-unIDed Chandra sources

countsaID
I241+I247
I186
I132+I135+I196+I203+I363
a Values in the 0.5–8.0 keV range.

NH b
kB T bLX a(1022 cm−2 )(keV)(ergs s−1 )55 5.83 (0.0–6.0) 2.80 (1.9–...) 1.00e+30
66 14.2 (0.0–41) 1.91 (0.5–...) 2.07e+30
66 20.2 (8.0–42) 3.71 (1.0–...) 3.47e+30

For combined fittings, the sum of all sources are shown for the count andluminosity.
b The lower and upper limit (1 σ) are given in parentheses.

Some have too few spectral bins to derive theuncertainty of their best-fit parameters.

objects for the following reasons.
First, it has no NIR counterpart brighter than the QUIRC limiting magnitude of K
∼ 16.5 mag. I132 at MMS 3, which was observed with the Subaru deep imaging observation,
has much tighter upper limit of K ∼ 19.6 mag. Low-mass class I protostars are generally
detected at 10–14 mag and class II at 8–12 mag in the K band at the distance of 450 pc (forexample, see Fig. 24. in Aspin, Sandell, & Russel 1994[12] ), hence are easily detected with our
K -band sensitivity. In fact, all class I and class II sources with X-ray emissions (Table A.1)
have the K -band magnitude of 6.5–15.1 mag and 9.3–15.3 mag, respectively. These six Xray sources are fainter than typical class I protostars by more than 10–100 times in the Kband, which indicates that these sources are either much more obscured than typical class I
protostars, or are intrinsically faint in NIR because of their much lower mass than low-masssources.
Our results of the X-ray spectral analysis on these sources favor the high obscurationinterpretation. The spectrum of the brightest source (I186) and the combined spectrum of
the rest of faint others (I132, I135, I196, I203, and I363) are well fitted with a thin-thermal
plasma model (Fig. 9.10) with the best-fit value of LX = 0.5–2.0×1030 ergs s−1 (Table 9.7).
Here, we assumed that the LX values are the same for I132, I135, I196, I203, and I363,
because they have the same order of X-ray counts (Table A.1). If these sources follow the
relation between the mass and LX (Fig. 9.3), this X-ray luminosity corresponds to the sourceof 0.1–0.5 M¯ . If these X-ray sources are in this mass range with moderate extinction, theyshould be easily detected at the detection limit of our deep NIR observations. This rules out
the possibility of these sources just to have a very low mass.

9.3. X-RAY EMISSIONS FROM NIR-UNIDED SOURCES

215

Second, they have much larger NH values of 1–2×1023 cm−2 than typical class I sources(Table 9.5). This is converted to AV ≈ 100 mag using the equation (7.6).
Third, some of the sources spatially coincide with the 350 µm cores (Lis et al. 1998[117] ),which provides the position of protostellar cores with a better spatial resolution than 1.3 mm
mapping observations by Chini et al. (1997)[35] . I132 and I186 are located within thepositional uncertainty of ∼500 respectively from CSO 7 and CSO 19, and I363 is within 900
from CSO 15. I132 is also associated with MMS 3, a class 0 candidate source, detected by
1.3 mm mapping observations (Chini et al. 1997[35] ).
These sources, if they are class 0 sources, would have magnetic activities in the same way
as class I protostars. The best-fit values of their kB T (2–3 keV) and LX (0.5–2.0×1030 ergs s−1 )is in the typical range of that of class I sources, which supports this idea. We may see thehigher temperature component of these sources.
We note that no X-ray emissions from bona-fide class 0 sources were found in other star
forming regions (e.g., NGC 2068) that were observed by Chandra with better sensitivity (E.
D. Feigelson 2002, private communication). However, our X-ray observations are as deepas, or deeper than any other wavelength observations with unprecedented spatial resolution
in this field. Just as an infrared source with no optical counterpart found by Becklin &Neugebauer (1967)[19] turned out to be a new class of YSOs in the Orion nebula, our X-ray
sources can be of this kind. Further studies are mandatory to identify the nature of thesesources, such as millimeter–sub-millimeter interferometer observations to detect circumstellar
clumps of these prospective YSOs.

216

CHAPTER 9. DISCUSSION

Chapter 10
Conclusions
Using OMC-2 and OMC-3 as our study field and taking a multi-wavelength observational
approach, we discussed the origins and mechanisms of ∼400 X-ray sources to understandthe wide variety of X-ray-emitting phenomena seen in star-forming regions.
1. We conducted deep X-ray and NIR observations respectively using ACIS on Chandra
and QUIRC on the University of Hawaii 88 inch (2.2 m) telescope. The X-ray observation is complete down to FX ∼ 10−14.5 ergs s−1 cm−2 with the faintest detected sourceof FX ∼ 10−15.5 ergs s−1 cm−2 in the 0.5–8.0 keV energy range. The NIR image has
the 90% completeness limit of J ∼ 17.5, H ∼ 16.5, and K ∼ 16.0 mag, matching wellwith the Chandra limit (Sects. 5.1 and 5.2).
2. We extracted 385 X-ray sources in the 17×17 arcmin2 ACIS-I FOV and 1448 NIR
sources in the 512 arcmin2 QUIRC FOV. Combining the 2MASS catalog with our
QUIRC source list and correlating them with our Chandra data, we identified the NIR
counterpart for 278 (∼72%) X-ray sources (Sects. 5.1 and 5.2). Most of NIR-IDed
X-ray sources are YSOs that belong to OMC-2 and OMC-3, considering their K -band
flux and luminosity function (Sect. 6.2).
3. The NIR-IDed X-ray sources were examined for their J -, H -, and K -band colors toestimate their mass, bolometric luminosity, and evolutional class (Sect. 6.2). Their
X-ray temporal and spectral features were also analyzed to derive their flux variability,
plasma temperature, emission measure, and X-ray luminosity (Sects. 7.1 and 7.2).
4. The averaged X-ray properties among different mass ranges were compared. We found
217

218

CHAPTER 10. CONCLUSIONS
that IM (2.0 M¯ ≤ M < 10.0 M¯ ), LM (0.2 M¯ ≤ M < 2.0 M¯ ), and VLM(M < 0.2 M¯ ) YSOs have the same X-ray emission mechanisms based on their Lbol /LX
values, LX -mass relation, and averaged X-ray features. This is in contrast with theHM (M ≥ 10.0 M¯ ) sources that emit X-rays of the stellar wind origin (Sect. 9.1).

5. We revealed that the X-ray emission from IM, LM, and VLM sources consists of two
components of different temperatures with kB T ∼ 1.0 keV and 2.0–3.0 keV. Basedon the time-sliced X-ray spectroscopy as well as comparison with the sun and othersources in the literature, we proposed that the soft component is from coronal and thehard component is from flare activities (Sect. 9.2).
6. Most of the NIR-unIDed X-ray sources are AGNs based on their X-ray spectra, HR
distribution, and the number counts. However, the spatial distribution of these sources
has an excess along the ridge of 1.3 mm cloud cores, indicating that ∼10 of them are
related to star formation (Sect. 8.1).
7. We conducted follow-up observations to identify the nature of the NIR-unIDed X-ray
sources associated with the 1.3 mm ridge using QUIRC on the University of Hawaii
88 inch (2.2 m) telescope in the H2 v = 1 − 0 S(1) band (Sect. 8.2), IRCS on the
Subaru telescope and NSFCam on IRTF in the J, H, K, L0 , and H2 v = 1 − 0 S(1)bands (Sect. 8.3) in addition to the centimeter interferometer imaging observation using
VLA (Sect. 8.4).
8. Four NIR-unIDed X-ray sources along the 1.3 mm ridge have many multi-wavelengthfeatures in common; association with the 1.3 mm cores, H2 , CO, HCO+ outflows,
and centimeter emissions from radio jets. These X-ray sources are very close to but
significantly offset from the class I NIR sources in the direction of the jet and outflow
system. We proposed a picture of the jet-induced plasma to account for these X-ray
emissions (Sect. 9.3).
9. We have six NIR-unIDed X-ray sources that are located along the 1.3 mm ridge but notwith the jet and outflow associations. Theses sources can be deeply embedded X-rayemitting YSOs such as class 0 objects, based on their X-ray luminosity, temperature,
NIR flux upper limit, and association of some with 350 µm and 1.3 mm cores (Sect. 9.3).

219

NIR
identification

yes

no

mass
(Mo)
<0.2
(VLM)

0.2-2.0(LM)

2.0-10(IM)

plasma temperature
(keV)

1.0

corona1.3 mm cloud
association
>10
(HM)

yes

magnetic
reconnections

jet/outflow
association

stellar wind2.0-3.0noyes

jet-incuded
plasmaFigure 10.1: Summarynodeeplyembedded
YSOs

AGNs

220

CHAPTER 10. CONCLUSIONS

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BIBLIOGRAPHY

Appendix A
Chandra Sources and NIR
Counterpart

235

I1
I2
I3
I4
I5
I6
I7
I8
I9
I10
I11
I12
I13
I14
I15
I16
I17
I18
I19
I20
I21
I22
I23
I24
I25
I26
I27
I28
I29
I30
I31
I32
I33
I34
I35
I36
(cont.)

IDa

R.A.b(hh:mm:ss.ss)
05:34:38.60
05:34:40.86
05:34:43.10
05:34:44.89
05:34:45.19
05:34:48.29
05:34:48.37
05:34:49.18
05:34:50.33
05:34:50.43
05:34:50.59
05:34:50.64
05:34:53.03
05:34:53.42
05:34:53.45
05:34:53.71
05:34:55.38
05:34:55.66
05:34:55.76
05:34:56.07
05:34:56.13
05:34:56.64
05:34:56.67
05:34:56.71
05:34:56.82
05:34:57.35
05:34:58.19
05:34:58.21
05:34:58.52
05:34:59.22
05:34:59.32
05:34:59.47
05:35:00.40
05:35:00.87
05:35:01.37
05:35:01.43

decl.b(dd:mm:ss.s)−05:08:42.8−05:06:58.2−05:09:18.0−05:06:49.1−05:10:45.1−05:07:13.1−05:05:01.1−05:04:38.2−05:06:38.1−05:11:11.2−05:06:49.8−05:04:07.6−05:03:26.9−05:10:28.2−05:01:30.2−05:05:48.9−05:01:39.3−05:08:44.3−05:07:42.5−05:00:55.6−05:06:01.5−05:06:26.1−05:04:37.9−05:10:43.6−05:11:33.5−05:06:04.0−05:09:27.9−05:11:54.6−05:12:27.0−05:01:26.2−05:05:30.0−05:08:25.6−05:09:44.8−05:09:39.4−05:11:06.1−05:09:32.8
PhotonCounts
255
63
368
403
176
535
549
127
70
773
110
361
1747
579
49
145
534
39
103
359
276
55
98
48
2286
19
558
258
135
28
740
30
213
135
60
670
0.31
−0.02
0.62
−0.54
−0.25
−0.66
−0.77
−0.97
−0.29
−0.75
0.40
−0.70
−0.73
−0.70
0.10
−0.75
−0.83
0.38
0.24
−0.69
−0.82
0.20
0.47
−0.33
−0.82
0.58
−0.71
−0.64
0.04
0.43
−0.75
0.27
0.13
−0.72
0.33
−0.85

HRc

Je
(mag)
16.22
15.50
11.88
12.17
12.99
12.48
12.55
13.96
11.96
12.65
11.95
12.22
14.34
13.33
12.51

12.80
12.56

13.46
10.89
12.29
12.65
14.03
12.41
13.81
13.01
13.86
12.13

TKK J05343791−0508480
TKK J05344064−0506586
2MASSI J0534449−050649
2MASSI J0534451−051047
2MASSI J0534482−050713
2MASSI J0534484−050501
2MASSI J0534492−050438
TKK J05345056−0506383
2MASSI J0534505−051110
2MASSI J0534506−050407
2MASSI J0534530−050327
2MASSI J0534534−051027
2MASSI J0534536−050129
2MASSI J0534537−050548
2MASSI J0534554−050139

2MASSI J0534561−050055
2MASSI J0534561−050601

2MASSI J0534567−051043
2MASSI J0534568−051132
2MASSI J0534581−050927
2MASSI J0534581−051153
2MASSI J0534586−051226
2MASSI J0534593−050530
2MASSI J0535003−050944
2MASSI J0535008−050938
2MASSI J0535014−051104
2MASSI J0535014−050932

NIR counterpartd

Table A.1: Chandra source list

0.57
0.56
0.96
0.67

0.77

0.76
0.60
0.55

0.73
0.71

0.64
0.61

0.72
0.75
0.63
0.62
0.64
0.73

0.72
0.75
0.66
0.68
0.69
0.51
0.66

J − He
(mag)
0.94
2.33

0.31
0.32
0.57
0.18

0.31

0.28
0.22
0.24

0.30
0.47

0.21
0.24

0.29
0.45
0.23
0.21
0.25
0.15

0.38
0.52
0.22
0.19
0.23
0.25
0.17

H − Ke
(mag)
0.25
1.28

III
III
II
III

III

III
III
III

III
others

III
III

III
II
III
III
III
III

III
others
III
III
III
III
III

othersIIIclassf0.090–0.100
0.130–0.150
0.150–0.175
0.300–0.350

0.250–0.300

0.300–0.350
0.175–0.200
0.080–0.090

0.130–0.150
0.900–0.950

0.150–0.175
0.175–0.200

0.200–0.250
0.350–0.400
0.250–0.300
0.075–0.080
0.130–0.150
0.250–0.300

0.350–0.400
0.300–0.350
0.150–0.175
0.200–0.250
0.200–0.250
0.080–0.090
0.300–0.350

massgh(M¯ )0.040–0.050
0.500–0.570

236
APPENDIX A. CHANDRA SOURCES AND NIR COUNTERPART

IDa
I37
I38
I39
I40
I41
I42
I43
I44
I45
I46
I47
I48
I49
I50
I51
I52
I53
I54
I55
I56
I57
I58
I59
I60
I61
I62
I63
I64
I65
I66
I67
I68
I69
I70
I71
I72
I73
I74
I75
(cont.)

R.A.b
05:35:01.98
05:35:02.16
05:35:02.52
05:35:02.56
05:35:02.79
05:35:02.79
05:35:02.85
05:35:03.12
05:35:03.30
05:35:03.33
05:35:03.41
05:35:03.81
05:35:03.99
05:35:04.23
05:35:04.30
05:35:04.45
05:35:04.55
05:35:04.64
05:35:05.24
05:35:05.65
05:35:05.66
05:35:05.76
05:35:05.95
05:35:06.09
05:35:06.36
05:35:06.49
05:35:06.58
05:35:06.61
05:35:06.71
05:35:06.83
05:35:07.54
05:35:08.04
05:35:08.75
05:35:08.96
05:35:09.15
05:35:09.32
05:35:09.42
05:35:09.85
05:35:10.14

decl.b
−05:00:43.2−05:04:38.5−05:04:10.0−05:04:58.5−05:03:03.9−05:00:01.9−05:02:00.6−05:09:17.3−05:04:48.1−05:13:07.2−05:05:40.4−05:05:19.1−05:01:41.1−05:08:42.5−05:08:12.9−05:07:36.5−04:58:29.9−05:09:56.1−04:59:23.2−04:58:53.6−05:04:53.4−05:11:34.5−05:08:37.5−05:12:17.0−05:09:00.0−04:58:40.4−05:07:16.0−05:04:51.2−05:11:45.4−05:10:39.1−05:11:14.7−05:01:18.2−05:04:40.5−05:10:25.6−05:06:47.1−04:59:32.2−04:59:41.2−04:58:49.1−05:13:40.6
Counts
63
83
11
9
20
1023
20
90
26
159
1771
17
20
54
25402
14
109
437
26
334
7
92
18
43
10
58
15
42
257
200
1232
14
26
12
1192
56
72
442
86

HRc
−0.46
−0.76
0.82
1.00
−0.40
−0.57
0.50
−0.76
0.69
0.17
−0.62
0.53
0.70
0.26
−0.55
−0.43
−0.21
−0.78
0.54
−0.83
0.43
−0.28
−0.67
−0.30
0.20
−0.45
0.60
0.43
−0.19
−0.76
−0.21
0.14
−0.85
−0.67
−0.83
0.39
−0.56
0.24
0.00

Je
14.51
13.88

15.83
12.29
13.15
15.07
9.17

8.18
14.75
12.83
11.38
11.94
12.91
15.17
8.13
14.21

13.85
12.59
12.38
16.19
12.37
14.56
11.24
12.89
16.22

NIR counterpartd
2MASSI J0535019−050043
2MASSI J0535021−050438

2MASSI J0535028−050303
2MASSI J0535027−050002
2MASSI J0535031−050917
TKK J05350365−0513104
2MASSI J0535034−050540

2MASSI J0535042−050812
TKK J05350440−0507356
2MASSI J0535046−045829
2MASSI J0535046−050955
2MASSI J0535056−045853
2MASSI J0535057−051135
2MASSI J0535058−050838
2MASSI J0535061−051216
2MASSI J0535063−045841

2MASSI J0535067−051145
2MASSI J0535068−051038
2MASSI J0535075−051114
TKK J05350779−0501193
2MASSI J0535087−050440
2MASSI J0535089−051025
2MASSI J0535091−050647
2MASSI J0535094−045941
TKK J05350988−0458495

0.68
3.04

1.44
0.67
1.07
0.93
0.74
0.61
0.67

0.56

1.39
1.08
0.00

0.65

0.66
1.10
1.05
0.65

1.69
0.22

0.72

0.58
1.17

J − He
0.63
0.76

0.35
1.64

0.62
0.24
0.58
0.43
0.36
0.10
0.21

0.30

0.66
0.50
0.00

0.24

0.15
0.54
0.74
0.26

0.74
0.03

0.34

0.00
0.45

H − Ke
0.22
0.37

III
III

III
III
III
III
III
III
III

III

III
III
III

III

III
III
II
III

III
III

III

othersIIIclassfIII
III

0.150–0.175
1.400–1.500

0.350–0.400
0.200–0.250
0.500–0.570
0.040–0.050
0.250–0.300
0.060–0.070
0.570–0.600

0.075–0.080

0.620–0.700
0.090–0.100
2.000–2.200

0.300–0.350>4.0000.110–0.130
0.350–0.400
0.500–0.570

0.200–0.250
1.400–1.400

0.150–0.175

0.030–0.040
0.620–0.700

massgh
0.072–0.075
0.110–0.130

237

IDa
I76
I77
I78
I79
I80
I81
I82
I83
I84
I85
I86
I87
I88
I89
I90
I91
I92
I93
I94
I95
I96
I97
I98
I99
I100
I101
I102
I103
I104
I105
I106
I107
I108
I109
I110
I111
I112
I113
I114
(cont.)

R.A.b
05:35:10.32
05:35:10.51
05:35:11.56
05:35:11.81
05:35:12.72
05:35:12.80
05:35:12.92
05:35:12.95
05:35:13.00
05:35:13.34
05:35:13.35
05:35:13.88
05:35:13.99
05:35:14.28
05:35:14.29
05:35:14.63
05:35:14.64
05:35:14.66
05:35:14.67
05:35:14.70
05:35:14.87
05:35:14.94
05:35:14.99
05:35:15.08
05:35:15.18
05:35:15.27
05:35:15.36
05:35:15.49
05:35:15.55
05:35:15.59
05:35:15.61
05:35:15.64
05:35:15.76
05:35:15.80
05:35:15.93
05:35:16.14
05:35:16.35
05:35:16.40
05:35:16.49

decl.b
−05:11:11.1−04:58:45.5−05:02:08.2−05:14:00.0−05:12:00.8−05:01:46.1−04:55:55.7−05:02:08.5−05:00:26.2−05:09:19.9−05:04:14.5−04:58:03.2−05:07:38.8−05:14:26.3−05:13:40.3−05:06:25.3−05:02:24.7−05:03:12.4−05:08:52.3−05:08:26.2−05:06:48.8−05:01:18.3−05:07:13.2−05:06:53.6−05:07:56.4−05:00:32.6−05:13:40.2−05:01:12.2−05:01:43.5−05:09:32.2−04:59:27.3−04:57:12.7−05:12:27.4−05:03:26.0−05:14:59.5−05:09:19.3−05:04:36.3−04:58:01.9−05:03:30.2
Counts
13
835
16
237
59
79
325
109
29
1088
7
207
21
268
116
34
312
574
33
4
333
24
62
112
4
29
68
26
34
21
151
159
72
177
3013
88
17
264
294

HRc
0.54
0.52
0.75
−0.09
−0.46
−0.95
0.48
−0.83
0.38
−0.74
0.71
0.11
0.81
0.01
0.00
−0.65
−0.82
−0.85
−0.76
1.00
0.16
0.58
0.71
0.21
0.50
−0.86
−0.53
−0.31
−0.53
−0.33
−0.30
−0.47
0.06
−0.92
0.20
−0.91
−0.76
−0.79
−0.80

Je
>20.55
13.76
14.11
13.93
12.82
14.38
>20.68
12.14
15.63
15.19
16.30
14.39
12.77
12.45
12.83
16.75

15.89
13.42
13.47
14.34
13.66
13.93
14.63
13.30
18.18
13.69
11.57
12.91
14.57
13.22
12.23

NIR counterpartd
TKK J05351053−0458460
TKK J05351134−0514016
2MASSI J0535127−051200
2MASSI J0535128−050146
TKK J05351310−0455523
2MASSI J0535129−050208
TKK J05351303−0500261
2MASSI J0535133−050919
2MASSI J0535138−045803
2MASSI J0535142−051427
2MASSI J0535143−051340
2MASSI J0535146−050625
TKK J05351464−0502250
2MASSI J0535146−050312
2MASSI J0535146−050852
TKK J05351486−0506489

2MASSI J0535150−050653
2MASSI J0535152−050033
TKK J05351533−0513382
2MASSI J0535154−050112
2MASSI J0535155−050143
2MASSI J0535156−050931
2MASSI J0535156−045927
2MASSI J0535156−045713
TKK J05351580−0512264
2MASSI J0535158−050326
TKK J05351596−0514591
2MASSI J0535161−050919
2MASSI J0535163−050436
2MASSI J0535164−045802
2MASSI J0535164−050330

0.63
0.86
0.68
1.09
0.59
1.90
0.77
2.99
0.58
0.44
0.62
0.56
0.60
0.66

2.29

2.23

2.40
1.94
1.16
1.02
0.68
0.57

2.36

0.97
0.52
0.59
1.88
0.56
>3.77
0.68

>6.77

J − He

0.26
0.12
0.34
0.53
0.28
1.09
0.32
1.26
0.34
>0.39
0.23
0.33
0.16
0.20

1.20

1.09

1.50
1.26
0.65
0.46
0.18
0.28

1.16

0.39
0.25
0.28
1.64
0.33
2.45
0.19

>3.28

H − KeIIIothers
III
III
III
II
III
othersIIIothers
II
III
III
III

III

III

II
II
II
III
III
III

III

III
III
III
I
III
II
III

othersclassf0.110–0.130
0.150–0.175
0.080–0.090
0.200–0.250
0.090–0.100
0.450–0.500
0.150–0.175
0.250–0.300
0.100–0.110
0.250–0.300
0.150–0.175
0.060–0.070
0.130–0.150
0.250–0.300

0.350–0.400

0.175–0.200

0.900–0.950
0.150–0.175
0.130–0.150
0.350–0.400
0.200–0.250
0.150–0.175

0.500–0.570

0.300–0.350

0.150–0.175
0.075–0.080
0.090–0.100
2.000–2.200
0.070–0.072...........

massgh238
APPENDIX A. CHANDRA SOURCES AND NIR COUNTERPART

IDa
I115
I116
I117
I118
I119
I120
I121
I122
I123
I124
I125
I126
I127
I128
I129
I130
I131
I132
I133
I134
I135
I136
I137
I138
I139
I140
I141
I142
I143
I144
I145
I146
I147
I148
I149
I150
I151
I152
I153
(cont.)

R.A.b
05:35:16.66
05:35:16.80
05:35:16.86
05:35:17.12
05:35:17.25
05:35:17.36
05:35:17.41
05:35:17.46
05:35:17.72
05:35:17.92
05:35:18.24
05:35:18.24
05:35:18.26
05:35:18.31
05:35:18.45
05:35:18.61
05:35:18.84
05:35:18.93
05:35:18.94
05:35:18.96
05:35:18.98
05:35:19.65
05:35:19.75
05:35:19.75
05:35:19.86
05:35:19.97
05:35:19.98
05:35:19.99
05:35:19.65
05:35:20.14
05:35:20.37
05:35:20.59
05:35:20.74
05:35:20.76
05:35:21.13
05:35:21.26
05:35:21.31
05:35:21.39
05:35:21.44

decl.b
−05:08:54.4−05:07:27.4−05:07:47.8−05:12:39.1−05:03:15.9−05:12:29.3−04:59:56.6−05:09:49.2−05:00:30.3−05:15:33.2−05:13:07.1−05:03:54.1−05:08:05.1−05:00:33.0−05:08:30.9−04:59:42.2−05:14:46.3−05:00:50.1−05:06:36.3−05:03:23.1−05:00:29.2−05:02:28.6−05:05:31.6−05:15:34.9−05:15:08.4−05:01:02.3−05:14:03.8−05:12:51.1−05:13:27.0−05:13:15.5−05:02:26.4−05:03:00.2−05:15:49.5−04:58:33.8−05:06:32.4−05:09:16.4−05:12:13.1−05:09:42.4−05:09:03.8
Counts
4
45
16
74
10
65
259
44
29
830
561
92
7
60
15
165
661
23
26
7
24
11
6
359
309
259
202
97
143
953
73
7
2276
673
109
2202
14667
29
142

HRc
0.50
−0.91
−0.62
−0.54
0.80
−0.66
0.20
−1.00
−0.17
−0.14
−0.40
−1.00
−0.14
0.93
−0.73
−0.71
−0.48
0.65
0.85
1.00
0.83
−0.82
0.67
0.67
0.25
0.83
0.03
0.86
0.08
0.05
−0.86
0.43
−0.12
−0.37
0.63
−0.81
−0.63
−0.79
−0.62

Je
14.92
13.81
13.51
13.70
17.26
13.31
15.29
11.47
11.31
9.29
16.86
17.67
13.75
13.78
12.45

14.47
17.41
12.93
>20.72
13.51
14.49
13.47
9.74
12.24
18.13
9.84
12.33
>20.95
8.36
8.71
13.71
12.23

NIR counterpartd
2MASSI J0535167−050727
2MASSI J0535168−050747
TKK J05351715−0512394
TKK J05351738−0512296
TKK J05351742−0459570
2MASSI J0535174−050949
2MASSI J0535177−050031
TKK J05351792−0515329
TKK J05351824−0513069
2MASSI J0535182−050354
TKK J05351830−0508048
TKK J05351833−0500329
2MASSI J0535184−050830
2MASSI J0535186−045942
TKK J05351886−0514456

2MASSI J0535196−050228
TKK J05351982−0515354
2MASSI J0535198−051508
TKK J05351998−0501024
TKK J05351980−0514054
2MASSI J0535200−051250
TKK J05351966−0513265
2MASSI J0535201−051315
2MASSI J0535203−050226
TKK J05352062−0503007
2MASSI J0535207−051549
2MASSI J0535207−045834
TKK J05352115−0506324
2MASSI J0535212−050916
2MASSI J0535213−051212
2MASSI J0535213−050942
TKK J05352147−0509037

2.55
1.61
>2.61
0.43
2.06
1.95
1.92
0.77
3.73
1.18
1.12
>2.52
0.55
0.60
0.69
0.92

0.65

0.62
2.67
0.58
2.22
>0.73
>0.99
0.04
2.31
3.25
0.59
0.58
0.81

0.49
0.99
0.62

J − He

2.51
1.03
3.95
0.38
1.31
1.25
1.31
0.20
2.44
0.56
0.46
3.14
0.49
0.18
0.49
>0.37

0.31

0.12
1.68
0.30
1.37
.......
.......
0.01
1.28
>3.73
0.23
0.20
0.34

0.34
0.54
0.08

H − KeI
II
I
others
II
II
II
III
II
III
III
I
II
III
others
III

III

III
II
II
II
......
......
III
III
I
III
III
III

othersIII
IIIclassf3.000–3.500
3.000–3.500
0.110–0.130
0.400–0.450

0.090–0.100
0.700–0.750
1.400–1.500>4.0000.300–0.350
1.400–1.400
3.500–4.000
0.570–0.600

0.175–0.200

0.075–0.080

0.100–0.110
0.250–0.300
0.110–0.130
0.500–0.570...........
...........
0.750–0.800
0.175–0.200
0.600–0.620
0.090–0.100
0.090–0.100
0.300–0.350

0.050–0.055
0.150–0.175
0.110–0.130

massgh

239

IDa
I154
I155
I156
I157
I158
I159
I160
I161
I162
I163
I164
I165
I166
I167
I168
I169
I170
I171
I172
I173
I174
I175
I176
I177
I178
I179
I180
I181
I182
I183
I184
I185
I186
I187
I188
I189
I190
I191
I192
(cont.)

R.A.b
05:35:21.50
05:35:21.56
05:35:21.57
05:35:21.86
05:35:21.87
05:35:21.91
05:35:21.92
05:35:21.94
05:35:22.11
05:35:22.34
05:35:22.35
05:35:22.40
05:35:22.45
05:35:22.55
05:35:22.67
05:35:23.13
05:35:23.20
05:35:23.22
05:35:23.33
05:35:23.33
05:35:23.44
05:35:23.51
05:35:23.53
05:35:24.34
05:35:24.58
05:35:24.61
05:35:24.66
05:35:24.87
05:35:25.03
05:35:25.07
05:35:25.17
05:35:25.17
05:35:25.22
05:35:25.24
05:35:25.36
05:35:25.40
05:35:25.44
05:35:25.53
05:35:25.64

decl.b
−05:01:53.5−05:09:39.2−05:09:49.9−04:56:48.7−05:07:01.9−04:59:17.7−05:03:50.6−05:14:28.3−05:15:05.9−04:59:52.9−05:07:39.2−05:08:05.2−05:09:11.3−05:08:00.8−05:14:12.0−05:00:35.9−05:13:43.9−05:08:44.0−04:57:20.5−05:08:21.8−05:10:52.1−05:07:13.8−05:15:24.1−05:01:20.4−05:11:29.7−05:11:58.9−05:09:27.6−05:06:21.3−05:09:09.6−05:10:23.5−05:05:09.1−05:15:38.8−05:08:23.8−05:09:27.6−05:07:20.4−05:10:48.3−05:06:52.3−04:57:22.8−05:07:57.4
Counts
97
76
260
93
838
15
8
345
479
23
507
833
415
921
206
13
164
13
182
59
1909
33
96
277
83
363
9
144
26
22
12
162
66
544
4
762
6
145
324

HRc
0.13
0.84
−0.64
0.08
−0.71
−0.20
0.25
−0.69
−0.32
0.65
0.02
0.21
−0.92
−0.34
−0.69
−0.08
0.04
−0.38
−0.63
0.19
−0.82
0.76
−0.25
0.58
−0.25
−0.81
0.56
0.68
−0.85
0.82
0.00
−0.06
0.94
−0.86
0.50
−0.83
1.00
0.10
−0.64

Je
18.24
13.98
12.88
13.64
10.93
15.26
11.75
12.75
14.76
10.88
11.35
11.19
11.69
16.30
13.02
>20.72
12.88
16.60
11.31
14.03
>20.80
12.11
11.71
16.86
15.63
14.54
14.86
11.67
11.77
11.60
13.32
11.77

NIR counterpartd
TKK J05352152−0501539
2MASSI J0535215−050938
2MASSI J0535215−050949
TKK J05352169−0456487
2MASSI J0535218−050701
TKK J05352188−0459197
2MASSI J0535219−051427
TKK J05352191−0515012
2MASSI J0535223−050739
2MASSI J0535224−050805
2MASSI J0535224−050911
2MASSI J0535225−050800
2MASSI J0535226−051411
TKK J05352308−0500364
2MASSI J0535231−051343
TKK J05352322−0508436
TKK J05352330−0457207
TKK J05352335−0508216
2MASSI J0535234−051051
TKK J05352348−0515234
TKK J05352434−0501205
2MASSI J0535246−051129
2MASSI J0535246−051158
TKK J05352469−0509264
2MASSI J0535248−050621
2MASSI J0535250−050909
2MASSI J0535251−051023
TKK J05352524−0515357
2MASSI J0535252−050927
2MASSI J0535254−051048
TKK J05352567−0457183
2MASSI J0535256−050757

0.73
0.66

0.60

0.69

0.89

0.66
>1.51
1.23
0.77
1.81
2.99
0.63
1.96

2.62
1.40
0.58
1.41
0.90
2.45
1.76
>5.77
0.83
2.40
0.63

0.75
0.90

J − He
3.23
0.84
0.78
0.70
0.95
1.42

0.16
0.89

0.13

0.23

0.68

0.41
4.69
0.67
0.51
1.49
1.85
0.32
1.87

1.65
0.87
0.12
0.53
0.52
1.38
0.74
1.77
0.10
1.78
0.25

0.23
0.32

H − Ke
1.92
0.71
0.53
0.11
0.56
0.80

III
othersIII

III

othersIII
I
III
others
I
II
III
I

II
II
III
III
II
III
III
othersothers
I
III

III
III

classfIIothersothersIII
II
II

0.130–0.150
0.350–0.400

0.350–0.400

0.400–0.450

0.620–0.700

0.950–1.000
0.450–0.500
0.090–0.100
2.000–2.200
0.072–0.075
0.400–0.450

0.090–0.100

0.200–0.250
0.250–0.300
0.500–0.570

2.000–2.200
3.000–3.500
0.400–0.450
2.700–3.000
0.620–0.700
0.350–0.400
1.400–1.400

0.450–0.500
0.250–0.300

massgh
0.350–0.400
0.110–0.130
0.200–0.250
0.110–0.130
1.400–1.500
0.130–0.150240
APPENDIX A. CHANDRA SOURCES AND NIR COUNTERPART

IDa
I193
I194
I195
I196
I197
I198
I199
I200
I201
I202
I203
I204
I205
I206
I207
I208
I209
I210
I211
I212
I213
I214
I215
I216
I217
I218
I219
I220
I221
I222
I223
I224
I225
I226
I227
I228
I229
I230
I231
(cont.)

R.A.b
05:35:25.72
05:35:25.73
05:35:25.77
05:35:25.85
05:35:25.86
05:35:26.05
05:35:26.27
05:35:26.29
05:35:26.34
05:35:26.47
05:35:26.66
05:35:26.85
05:35:27.07
05:35:27.15
05:35:27.41
05:35:27.45
05:35:27.63
05:35:27.73
05:35:27.78
05:35:27.83
05:35:28.06
05:35:28.14
05:35:28.18
05:35:28.19
05:35:28.21
05:35:28.27
05:35:28.50
05:35:28.60
05:35:28.67
05:35:28.71
05:35:29.02
05:35:29.25
05:35:29.45
05:35:29.81
05:35:29.89
05:35:29.90
05:35:30.00
05:35:30.11
05:35:30.13

decl.b
−05:07:03.4−05:09:49.7−05:05:57.9−05:02:45.2−05:07:56.5−05:08:37.9−05:07:41.1−05:08:40.1−05:16:12.0−04:59:52.0−05:06:10.1−05:11:07.9−05:06:21.7−05:15:45.3−05:09:04.0−05:02:42.1−05:09:36.8−05:13:55.6−05:17:03.0−05:05:36.1−05:01:34.8−05:10:13.5−05:03:40.9−05:00:49.2−05:11:37.2−04:58:38.0−05:07:46.8−05:05:44.2−05:03:06.1−05:05:51.2−05:06:03.8−05:08:05.3−05:16:33.5−05:16:07.6−05:12:10.6−05:04:26.7−05:12:27.7−05:09:09.5−05:14:19.0
Counts
5
1411
9
5
878
83
8
3840
231
88
11
289
12
196
18
270
24
55
711
345
326
37
41
172
50
1228
89
28
8
11
1424
6
1189
476
136
8
157
23
148

HRc
−1.00
−0.68
0.11
1.00
−0.79
−0.76
1.00
−0.84
−0.06
0.20
1.00
0.13
0.67
−0.08
−0.89
0.16
0.42
0.60
−0.46
0.57
0.42
−0.41
0.41
−0.79
−0.28
0.61
0.03
0.29
0.50
0.82
−0.82
0.67
−0.53
−0.63
−0.78
1.00
−0.61
−0.74
−0.27

Je
13.72
11.09
16.21
11.12
12.51
10.10
13.28
16.52
8.85
12.75
14.84
16.60
12.90
13.62
11.58
>20.62
18.99
11.16
20.03
12.49
12.76
>20.58
15.99
14.92

11.64
11.59
12.06
12.68
12.08
13.77
13.16

NIR counterpartd
2MASSI J0535257−050703
2MASSI J0535257−050949
TKK J05352576−0505579
TKK J05352587−0507564
TKK J05352606−0508377
2MASSI J0535262−050840
2MASSI J0535264−051612
TKK J05352646−0459519
2MASSI J0535268−051107
2MASSI J0535270−051544
2MASSI J0535274−050903
TKK J05352744−0502424
2MASSI J0535276−050937
2MASSI J0535275−051356
TKK J05352793−0516573
TKK J05352786−0505363
TKK J05352806−0501351
2MASSI J0535281−051013
TKK J05352819−0503413
2MASSI J0535281−050049
2MASSI J0535281−051137
TKK J05352826−0458384
TKK J05352852−0507469
2MASSI J0535285−050544

2MASSI J0535290−050604
2MASSI J0535294−051633
2MASSI J0535298−051606
2MASSI J0535299−051210
2MASSI J0535299−051227
2MASSI J0535301−050909
2MASSI J0535301−051418

0.70
0.60
1.18

0.86
0.78
0.65

0.58

0.89
0.77
3.32
2.44
1.28
0.73
>4.33
4.09
1.00
3.61
0.65
1.06
>6.47
2.99
2.58

1.04

0.50
1.46
2.34

0.17
0.59

J − He
0.65
0.61
1.75

0.49
0.27
0.61

0.26
0.31
0.20

0.17

0.51
0.45
2.22
1.50
0.66
0.27
2.79
2.69
0.66
4.62
0.22
0.52
2.65
1.88
1.50

0.77

0.22
0.76
1.26

0.86
1.91

H − Ke
0.28
0.34
1.80

others
III
III

III
III
III

III

II
III
II
II
III
III
II
II
II
I
III
III
others
II
II

II

II
III
III

othersothersclassfIII
III
I

0.300–0.350
0.100–0.110
0.350–0.400

0.620–0.700
0.350–0.400
0.175–0.200

0.350–0.400

1.500–1.600
1.500–1.600

1.400–1.400
1.400–1.400
0.200–0.250
0.200–0.250
0.350–0.400

0.250–0.300
0.072–0.075
1.900–2.000
3.500–4.000
0.300–0.350
0.500–0.570>4.0000.500–0.570
0.250–0.300

0.200–0.250
0.175–0.200

massgh
0.100–0.110
0.570–0.600
0.110–0.130

241

IDa
I232
I233
I234
I235
I236
I237
I238
I239
I240
I241
I242
I243
I244
I245
I246
I247
I248
I249
I250
I251
I252
I253
I254
I255
I256
I257
I258
I259
I260
I261
I262
I263
I264
I265
I266
I267
I268
I269
I270
(cont.)

R.A.b
05:35:30.32
05:35:30.55
05:35:30.64
05:35:30.72
05:35:30.86
05:35:31.06
05:35:31.22
05:35:31.27
05:35:31.31
05:35:31.46
05:35:31.48
05:35:31.49
05:35:31.57
05:35:31.58
05:35:31.61
05:35:31.91
05:35:31.96
05:35:32.02
05:35:32.24
05:35:32.31
05:35:32.35
05:35:32.35
05:35:32.51
05:35:32.80
05:35:32.86
05:35:32.97
05:35:33.00
05:35:33.16
05:35:33.37
05:35:33.52
05:35:33.61
05:35:33.64
05:35:33.83
05:35:33.86
05:35:34.26
05:35:34.48
05:35:34.52
05:35:34.68
05:35:35.11

decl.b
−05:13:52.0−05:03:33.9−04:59:35.6−05:06:45.3−04:58:12.4−05:04:14.2−05:12:28.3−05:12:01.8−05:15:33.3−05:05:45.5−05:16:03.2−05:05:01.4−05:05:47.1−05:16:56.4−05:00:14.0−05:05:49.3−05:09:27.9−05:08:05.2−05:11:58.3−05:11:44.0−05:14:26.3−05:08:29.8−05:02:09.9−05:07:51.6−05:16:04.6−05:12:05.9−05:17:32.3−05:14:11.1−05:08:02.0−05:15:19.3−05:00:41.7−05:03:07.7−05:04:27.2−05:09:05.6−04:59:52.7−05:13:07.3−05:00:51.8−05:15:53.3−05:14:47.2
Counts
213
13
222
6
67
91
311
82
2773
22
660
187
13
181
63
33
2062
7
38
175
150
25
14
23
1143
25
406
974
11
646
128
223
346
20
53
76
27
330
99

HRc
−0.10
−0.08
−0.34
0.33
0.25
−0.93
−0.80
−0.41
−0.64
0.91
−0.78
−0.80
0.85
−0.28
0.49
0.39
−0.65
−0.14
−0.53
0.29
−0.45
0.76
−0.71
0.65
−0.39
0.12
−0.63
−0.14
0.82
−0.11
−0.83
−0.35
0.88
−0.80
0.89
−0.61
0.48
−0.67
0.33

Je
13.19
15.31
14.31
17.60
11.13
13.03
14.57
10.05
5.86
11.96
11.72
12.95
14.25
9.34
15.16
12.61
14.58
12.62
14.71
11.59
13.77
12.81
12.36
13.08
11.93
13.06
13.75
13.99
14.14
15.79
13.33

NIR counterpartd
2MASSI J0535302−051352
TKK J05353054−0503345
2MASSI J0535306−045936
TKK J05353080−0458136
2MASSI J0535310−050415
2MASSI J0535312−051228
2MASSI J0535313−051201
2MASSI J0535312−051533
2MASSI J0535313−051602
2MASSI J0535315−050501
2MASSI J0535315−050547
2MASSI J0535316−051658
2MASSI J0535316−050014
2MASSI J0535319−050927
2MASSI J0535320−050805
2MASSI J0535321−051157
2MASSI J0535323−051143
2MASSI J0535324−051424
2MASSI J0535325−050209
2MASSI J0535329−051605
2MASSI J0535329−051204
2MASSI J0535331−051733
2MASSI J0535331−051410
TKK J05353359−0515232
2MASSI J0535336−050042
2MASSI J0535336−050308
2MASSI J0535338−050427
2MASSI J0535338−050905
2MASSI J0535345−051307
2MASSI J0535345−050052
2MASSI J0535346−051552

0.58
2.31
0.56

1.24
0.65
1.45
1.93
0.59

1.09
2.04
0.62
0.78

0.60

0.81
1.05
0.75
2.18
0.98

0.23
0.69
2.00
1.17
2.63

3.13
0.57
0.66
0.62
0.78

J − He
1.61
1.67
2.29

0.16
2.17
0.55

0.38
0.20
0.69
1.26
0.26

0.30
1.15
0.27
0.40

0.19

0.41
0.62
0.48
1.14
0.36

0.05
0.48
1.42
0.50
1.64

1.65
0.12
0.23
0.30
0.32

H − Ke
0.85
0.87
1.52

III
I
othersothers
III
III
II
III

others
III
III
III

III

II
II
III
III
III

III
others
II
III
II

III
II
III
III
III

classfIII
III
II

0.080–0.090
0.400–0.450
0.110–0.130

0.080–0.090

0.400–0.450
0.300–0.350
0.620–0.700

1.400–1.400
0.150–0.175
0.300–0.350

0.060–0.070

3.000–3.500
0.080–0.090
0.200–0.250
0.900–0.950
0.350–0.400>4.0000.350–0.400>4.0000.400–0.450
2.700–3.000

0.500–0.570
0.500–0.570
0.150–0.175
0.070–0.072
2.000–2.200

massgh
0.900–0.950
0.175–0.200
1.400–1.500

242
APPENDIX A. CHANDRA SOURCES AND NIR COUNTERPART

IDa
I271
I272
I273
I274
I275
I276
I277
I278
I279
I280
I281
I282
I283
I284
I285
I286
I287
I288
I289
I290
I291
I292
I293
I294
I295
I296
I297
I298
I299
I300
I301
I302
I303
I304
I305
I306
I307
I308
I309
(cont.)

R.A.b
05:35:35.12
05:35:35.36
05:35:35.48
05:35:35.55
05:35:35.63
05:35:35.64
05:35:35.71
05:35:36.02
05:35:36.19
05:35:36.40
05:35:36.51
05:35:36.56
05:35:36.69
05:35:36.77
05:35:36.86
05:35:36.95
05:35:37.17
05:35:37.57
05:35:37.70
05:35:38.04
05:35:38.07
05:35:38.30
05:35:38.52
05:35:38.57
05:35:38.65
05:35:38.75
05:35:38.88
05:35:39.03
05:35:39.08
05:35:39.17
05:35:39.39
05:35:39.72
05:35:39.97
05:35:40.19
05:35:40.47
05:35:40.59
05:35:40.66
05:35:40.80
05:35:41.04

decl.b
−05:05:58.2−05:11:11.8−05:07:20.2−05:06:58.5−05:01:48.5−05:10:50.0−05:15:43.3−05:12:25.1−05:04:55.8−05:01:15.2−05:05:22.3−05:04:39.1−05:04:14.0−05:09:59.1−05:07:32.4−05:05:25.8−05:10:29.6−05:04:47.5−05:06:31.8−05:15:08.3−05:03:17.1−05:14:19.1−04:59:40.2−05:08:03.4−05:09:56.9−05:04:55.3−05:12:42.2−05:07:04.1−05:08:56.4−05:05:40.0−05:05:07.7−04:59:18.4−05:06:36.5−05:04:27.3−05:04:18.7−05:12:19.8−05:11:10.0−05:09:01.1−05:06:24.9
Counts
13
506
27
210
66
22
204
270
114
943
9
909
2221
11
10
24
312
16
298
122
13
246
518
75
320
40
1047
279
198
7
113
65
75
9
19
85
76
825
119

HRc
1.00
−0.72
0.93
−0.90
0.91
−0.55
−0.26
−0.61
0.60
−0.46
0.33
−0.92
−0.67
−0.45
0.60
−0.33
−0.88
0.12
−0.64
0.48
0.38
−0.42
−0.31
0.12
−0.72
−0.55
−0.26
−0.84
−0.80
0.14
0.59
0.35
−0.68
0.33
0.58
−0.13
0.11
−0.61
−0.76

Je
12.66
13.35
14.24
11.63
11.09
13.17
10.89
12.24
11.96
13.30
14.59
12.53
17.46
12.95

11.56
12.00
15.96
13.06
14.96
10.81
12.60
10.86

12.67

12.96
13.77
10.33
12.66

NIR counterpartd
2MASSI J0535353−051111
2MASSI J0535355−050658
2MASSI J0535356−051050
2MASSI J0535356−051543
2MASSI J0535360−051225
2MASSI J0535362−050455
2MASSI J0535364−050115
2MASSI J0535365−050439
2MASSI J0535366−050414
2MASSI J0535367−051000
2MASSI J0535369−050526
2MASSI J0535371−051029
TKK J05353759−0504471
2MASSI J0535376−050631

2MASSI J0535382−051418
TKK J05353853−0459410
2MASSI J0535385−050803
2MASSI J0535386−050956
2MASSI J0535387−050455
2MASSI J0535388−051241
2MASSI J0535390−050704
2MASSI J0535390−050856

2MASSI J0535399−050636

2MASSI J0535406−051219
2MASSI J0535407−051111
2MASSI J0535407−050901
2MASSI J0535410−050625

0.69
0.65
0.90
0.62

1.13

0.75
0.92
2.53
0.58
1.94
1.11
0.56
0.66

0.51
0.68
2.62
0.67

0.65
0.75
0.80

0.52
0.68
1.55
1.35
0.84

0.63

0.58

J − He

0.27
0.29
0.30
0.30

0.61

0.22
>0.62
1.36
0.30
1.03
0.66
0.29
0.16

0.43
0.27
1.59
0.28

0.19
0.32
0.56

0.35
0.28
1.04
0.72
0.47

0.21

0.22

H − Ke

III
III
II
III

III

III
II
III
III
III
II
III
III

others
III
II
III

III
III
others

III
III
II
III
II

III

III

classf0.150–0.175
0.100–0.110
2.200–2.500
0.175–0.200

0.450–0.500

0.500–0.570
0.500–0.570
0.500–0.570
0.130–0.150
0.350–0.400
2.200–2.500
0.150–0.175
0.750–0.800

0.060–0.070
0.200–0.250
0.200–0.250
0.150–0.175

0.250–0.300
0.350–0.400
0.150–0.175

0.072–0.075
0.400–0.450
3.000–3.500
0.450–0.500
1.400–1.400

0.110–0.130

0.150–0.175

massgh

243

IDa
I310
I311
I312
I313
I314
I315
I316
I317
I318
I319
I320
I321
I322
I323
I324
I325
I326
I327
I328
I329
I330
I331
I332
I333
I334
I335
I336
I337
I338
I339
I340
I341
I342
I343
I344
I345
I346
I347
I348
(cont.)

R.A.b
05:35:41.38
05:35:41.72
05:35:41.81
05:35:42.04
05:35:42.04
05:35:42.40
05:35:42.64
05:35:42.78
05:35:42.98
05:35:43.27
05:35:43.54
05:35:43.82
05:35:44.52
05:35:44.54
05:35:44.88
05:35:45.70
05:35:46.10
05:35:47.25
05:35:47.77
05:35:48.26
05:35:48.39
05:35:48.40
05:35:48.88
05:35:49.00
05:35:49.04
05:35:49.21
05:35:49.96
05:35:50.07
05:35:50.51
05:35:51.12
05:35:51.46
05:35:51.61
05:35:51.66
05:35:52.66
05:35:53.71
05:35:53.86
05:35:54.05
05:35:54.22
05:35:54.67

decl.b
−05:03:52.6−05:03:28.3−05:05:19.1−05:10:12.0−05:13:00.0−05:11:02.5−04:59:55.4−05:11:55.1−05:03:05.3−05:09:16.8−05:05:40.2−05:09:59.8−05:07:31.4−05:00:04.9−05:07:16.7−05:06:44.7−05:10:52.4−05:02:50.1−05:10:31.2−05:11:15.5−05:05:20.6−05:01:27.9−05:00:31.6−05:05:42.2−05:01:40.6−05:02:23.2−05:04:24.4−05:10:22.2−05:02:24.7−05:07:08.7−05:02:03.7−05:05:58.7−05:08:09.0−05:05:05.2−05:02:33.8−05:06:54.3−05:04:14.5−05:05:43.2−05:06:28.6
Counts
38
61
15
660
617
56
79
658
42
2262
48
174
288
45
5273
74
695
64
3604
60
67
193
88
31
288
49
88
63
63
1348
167
48
7972
4600
164
258
1398
74
168

HRc
−0.58
−0.74
−0.33
−0.32
−0.73
0.32
0.34
−0.79
−0.33
−0.79
−0.08
−0.67
−0.87
0.24
−0.70
0.51
−0.76
0.41
−0.81
0.07
0.55
−0.60
−0.45
0.10
−0.49
0.55
0.39
−0.33
0.27
−0.78
0.46
0.25
−0.73
−0.75
−0.07
0.34
−0.81
−0.03
−0.56

Je
14.21
13.45
15.52
11.47
13.45

11.18
13.34
10.76
11.96
13.69
12.25
14.91
10.07
11.83
10.18
12.77
11.84
12.63
12.59

13.21
11.00

10.04
9.82
13.12
11.29
13.55
13.48

NIR counterpartd
2MASSI J0535413−050352
2MASSI J0535417−050329
2MASSI J0535417−050519
2MASSI J0535420−051011
2MASSI J0535420−051259

2MASSI J0535427−051154
2MASSI J0535430−050307
2MASSI J0535432−050917
2MASSI J0535435−050541
2MASSI J0535438−050958
2MASSI J0535445−050731
TKK J05354461−0459576
2MASSI J0535448−050716
2MASSI J0535461−051051
2MASSI J0535477−051030
TKK J05354826−0511103
2MASSI J0535483−050128
TKK J05354884−0500285
2MASSI J0535489−050139

TKK J05355012−0510294
2MASSI J0535510−050708

2MASSI J0535516−050809
2MASSI J0535526−050505
2MASSI J0535535−050234
2MASSI J0535540−050414
2MASSI J0535542−050545
2MASSI J0535546−050627

0.87
0.65
0.55

0.62
0.58
1.04

0.74

0.58

0.77

0.93
0.96

0.54
0.82

0.78

0.70
0.64
0.68
0.87
0.60
0.70
0.65
0.63

J − He
1.17
0.61
1.70
1.33
0.56

0.49
0.20
0.30

0.14
0.37
0.35

0.37

0.24

0.35

0.68
0.29

0.21
0.26

0.41

0.16
0.27
0.17
0.69
0.27
0.20
0.22
0.25

H − Ke
0.49
0.20
0.83
0.62
0.29

II
III
III

III
III
III

III

III

II

II
II

II
III

III

III
III
II
others
III
II
III
II

classf
III
III
III
III
III

0.900–0.950
0.110–0.130
0.100–0.110

1.500–1.600
1.600–1.700
0.250–0.300

0.900–0.950

0.110–0.130

0.250–0.300

0.570–0.600
0.350–0.400

1.400–1.400
0.200–0.250

0.450–0.500

0.620–0.700
0.110–0.130
0.900–0.950
0.450–0.500
0.100–0.110
0.250–0.300
0.060–0.070
1.500–1.600

massgh
0.150–0.175
0.110–0.130
0.150–0.175
2.000–2.200
0.110–0.130

244
APPENDIX A. CHANDRA SOURCES AND NIR COUNTERPART

IDa
I349
I350
I351
I352
I353
I354
I355
I356
I357
I358
I359
I360
I361
I362
I363
I364
I365
I366
I367
I368
I369
I370
I371
I372
I373
I374
I375
I376
I377
I378
I379
I380
I381
I382
I383
I384
I385
S1
S2
(cont.)

R.A.b
05:35:55.86
05:35:57.79
05:36:00.05
05:36:00.36
05:36:00.55
05:36:04.60
05:34:54.47
05:34:57.03
05:35:08.43
05:35:13.13
05:35:18.87
05:35:21.33
05:35:21.50
05:35:22.42
05:35:22.67
05:35:29.78
05:35:30.67
05:35:31.19
05:35:33.14
05:35:47.84
05:35:50.91
05:34:44.08
05:34:52.91
05:35:00.97
05:35:07.89
05:35:10.79
05:35:14.97
05:35:19.73
05:35:29.82
05:35:30.76
05:35:33.75
05:35:35.70
05:35:38.44
05:35:42.37
05:35:44.67
05:35:46.94
05:35:54.84
05:35:54.73
05:35:56.14

decl.b
−05:04:42.5−05:05:02.8−05:04:32.2−05:05:50.5−05:05:03.5−05:04:00.5−05:04:12.5−05:02:50.2−05:12:24.5−05:07:51.5−05:09:51.4−05:12:46.3−05:07:26.0−05:02:40.7−05:06:49.5−04:59:53.9−05:04:09.9−05:09:15.7−05:15:08.7−05:08:21.5−05:01:04.9−05:05:58.3−05:08:03.2−05:05:39.6−05:09:03.5−05:10:43.5−05:04:43.1−05:11:43.5−05:13:29.1−05:03:35.5−04:59:26.9−05:09:07.4−05:10:08.7−05:02:50.3−05:00:38.6−05:06:58.9−05:05:25.8−04:58:07.1−04:56:55.9
Counts
87
169
134
68
413
250
18
6
34
4
5
15
4
4
3
27
4
8
268
28
91
57
18
8
3
3
3
34
49
5
15
6
28
15
31
14
23
2987
1681

HRc
0.24
0.14
−0.27
0.06
−0.27
0.10
0.67
1.00
0.47
1.00
1.00
0.47
1.00
1.00
1.00
0.63
1.00
1.00
0.26
0.57
0.45
0.30
0.00
−0.75
−1.00
−1.00
−1.00
0.00
0.18
−1.00
−0.07
−0.33
−0.50
−0.60
−0.55
−0.29
−0.30
−0.87
−0.75

Je
16.88
13.54
13.38
12.22
12.75
18.31

15.88

17.93
18.18
13.53

15.81

15.25

14.85
14.04
16.87
10.40
11.74

NIR counterpartd
TKK J05355574−0504377
2MASSI J0535599−050430
TKK J05360045−0505540
TKK J05360033−0505000
TKK J05360415−0504088
TKK J05345731−0502508

TKK J05352138−0512444

TKK J05352956−0459567
TKK J05353065−0504111
TKK J05353244−0515067

2MASSI J0535009−050540

TKK J05353072−0503355

2MASSI J0535384−051009
2MASSI J0535447−050039
TKK J05355468−0505213
2MASSI J0535546−045808
2MASSI J0535560−045655

1.10
0.48
0.62

0.75

0.61

1.66

0.41

1.30

0.77
1.76

0.70

1.82

0.57
0.55
0.57
0.74

J − He
1.26

0.67
0.17
0.19

0.35

0.31

0.81

0.35

0.75

1.08
1.39

0.53

0.77

0.41
0.19
0.19
0.31

H − Ke
1.44

II
III
III

III

III

III

othersIIothersIIothersothersothersIII
III
IIIclassfI

0.040–0.050
0.750–0.800
0.350–0.400

0.100–0.110

0.060–0.070

0.175–0.200

0.030–0.040

0.300–0.350<0.0020.040–0.050

0.040–0.050

0.040–0.050

0.100–0.110
0.110–0.130
0.200–0.250
0.200–0.250

massgh
0.040–0.050

245

R.A.b
05:35:56.28
05:35:58.84
05:35:59.31
05:36:02.99
05:36:04.24
05:36:05.75
05:36:11.84
05:36:12.81
05:36:28.11
05:36:14.94
05:36:20.26

decl.b
−04:55:04.1−04:55:35.2−04:58:44.3−04:57:34.4−04:57:42.5−04:51:08.5−05:00:30.4−04:55:13.7−04:57:07.5−04:57:05.9−04:54:22.2
Counts
510
799
743
304
285
832
567
462
185
72
164

HRc
0.13
0.03
−0.64
−0.30
−0.25
−0.39
−0.47
−0.29
0.43
0.47
0.34

Je
>15.42
12.55

12.23

NIR counterpartd
2MASSI J0535588−045537
2MASSI J0535592−045846

2MASSI J0536118−050032

0.69

>0.36
0.70

J − He

0.17

0.81
0.16

H − Ke

III

II
III

classf0.250–0.300

0.200–0.250

massghexcess, and Hα emission data (see Sect. 6.2).

for I200 and I256.

h Four sources have two estimates of their mass on Figure 6.7; i.e., 1.050–1.000 M¯ or 1.300–1.400 M¯ for I139 and I264, and 1.100–1.150 M¯ or 1.400–1.400 M¯

g The mass of NIR-IDed Chandra sources estimated from the J /(J –H ) color-magnitude diagram (see Sect. 6.2).

f The evolutional classes of NIR-IDed Chandra sources estimated from the NIR excess, U V

e NIR colors in the CIT color system.

d The QUIRC and 2MASS counterpart has the prefix “TKK J” and “2MASSI J”, respectively. The nomenclatures follow the IAU convention.

c Defined as (H − S)/(H + S) where H and S are the X-ray photon counts in the hard (2.0–8.0 keV) and soft (0.5–2.0 keV) band, respectively.

b The equinox in J2000.0.

of ACIS-S2.

keV) image of ACIS-I and ACIS-S2. I370–I385 are detected only in the soft band (0.5–2.0 keV) image of ACIS-I. No new source was detected in the soft band imagea I1–I354 and S1–S11 are detected in the total band (0.5–8.0 keV) image of ACIS-I and ACIS-S2. I355-I369 and S12-S13 are detected only in the hard band (2.0–8.0

IDa
S3
S4
S5
S6
S7
S8
S9
S10
S11
S12
S13

246
APPENDIX A. CHANDRA SOURCES AND NIR COUNTERPART

Appendix B
QUIRC Sources and 2MASSCounterpart

247

R.A.a1 34:28.94
2 34:29.36
3 34:29.48
4 34:29.60
5 34:29.86
6 34:30.15
7 34:30.27
8 34:30.61
9 34:30.97
10 34:31.07
11 34:31.47
12 34:31.52
13 34:31.58
14 34:31.85
15 34:32.03
16 34:32.05
17 34:32.36
18 34:32.55
19 34:32.88
20 34:32.89
21 34:33.26
22 34:33.27
23 34:34.06
24 34:34.16
25 34:34.17
26 34:34.62
27 34:34.66
28 34:35.55
29 34:35.55
30 34:35.95
31 34:36.14
32 34:36.26
33 34:36.35
34 34:36.39
35 34:36.69
36 34:36.69(cont.)

ID−5:08:38.7−5:11:14.4−5:05:24.7−5:04:29.0−5:04:05.6−5:11:56.7−5:11:48.2−5:11:05.0−5:03:56.9−5:06:17.1−5:08:54.1−5:12:30.0−5:11:50.3−5:04:09.3−5:10:23.2−5:11:24.8−5:12:59.6−5:04:21.3−5:10:15.5−5:09:30.9−5:07:26.8−5:11:44.1−5:12:27.0−5:05:57.0−5:05:17.1−5:04:49.7−5:05:08.4−5:08:45.0−5:09:04.8−5:09:03.2−5:05:08.0−5:00:48.2−5:02:54.7−5:11:40.6−5:05:03.4−5:08:17.5

decl.a

J bcd
(mag)
15.52
17.45
17.64
14.05
12.83
15.70
11.53
13.90
16.94
17.42
16.45
9.49†
17.78
13.31
15.21
13.01
18.64
17.65
16.25
20.34
14.51
17.50
15.37
17.18
13.30
14.02
16.22
17.42
17.43
16.10
16.34
19.98
16.61
14.82
16.05
18.13

H bcd
(mag)
14.13
16.75
16.82
13.47
12.16
14.35
10.64†
13.30
16.14
16.64
15.84
8.40†
16.59
12.66
14.63
12.19
15.67
16.83
15.33
>20.72
14.22
16.44
14.43
16.44
12.71
13.25
15.37
16.49
16.77
15.27
15.48
18.96
15.67
14.19
15.23
17.49

K cd
(mag)
13.74
16.51
16.44
13.15
11.95
13.99
9.95†
13.08
15.80
16.23
15.56
7.95†
16.21
12.50
14.51
11.83
15.12
16.63
15.06
17.05
13.85
16.00
14.14
16.12
12.40
13.03
15.18
16.19
16.46
14.94
15.46
16.79
15.40
14.12
15.05
16.55
0534363−051140
0534366−050503

0534359−050903
0534361−050507

0534341−050516
0534346−050449
0534346−050508

0534340−051227

0534332−050726

0534328−051015

0534318−050408
0534320−051023
0534320−051124

0534315−051230

0534295−050428
0534298−050405
0534301−051156
0534302−051148
0534305−051104

2MASS
counterpart
0534289−050838

R.A.a

37
34:36.72
38
34:36.76
39
34:36.83
40
34:36.84
41
34:36.92
42
34:36.93
43
34:37.03
44
34:37.63
45
34:37.80
46
34:37.91
47
34:37.91
48
34:38.00
49
34:38.0850
34:38.13
51
34:38.13
52
34:38.16
53
34:38.34
54
34:38.39
55
34:38.49
56
34:38.57
57
34:38.58
58
34:38.74
59
34:38.86
60
34:38.90
61
34:38.90
62
34:39.20
63
34:39.24
64
34:39.29
65
34:39.35
66
34:39.38
67
34:39.43
68
34:39.75
69
34:39.78
70
34:39.86
71
34:39.88
72
34:39.97(cont.)ID

Table B.1: QUIRC source list

−5:09:37.3−5:01:55.3−5:06:09.9−5:05:19.8−5:05:11.9−5:08:14.5−5:12:39.1−5:04:49.3−5:14:29.4−5:08:48.0−5:13:32.3−5:14:06.4−5:13:09.7−5:03:05.5−5:04:57.9−5:05:17.2−5:01:26.0−5:02:06.5−5:10:42.2−5:04:19.5−5:00:44.9−5:04:05.7−5:04:40.7−5:02:36.6−5:14:28.5−5:04:52.9−5:01:48.9−5:00:47.1−5:11:35.1−5:01:46.7−5:03:43.7−5:03:06.2−5:00:34.0−5:02:13.2−5:07:59.7−5:04:08.8

decl.a

J bcd
(mag)
17.71
20.87
15.74
17.75
16.92
17.01
16.80
16.82
15.17
16.25
14.46
16.77
16.75
16.26
12.30
14.35
15.26
19.60
16.42
15.73
16.12
15.72
16.05
13.65
14.45
16.44
13.81
14.62
18.24
12.86
18.09
12.95
16.19
16.73
16.48
15.91

H bcd
(mag)
16.98
19.90
14.96
16.71
16.46
16.77
15.41
15.79
14.08
15.28
13.93
16.17
15.73
15.26
11.70
13.84
14.24
19.02
15.49
14.78
15.30
15.18
15.26
12.91
13.34
15.01
13.24
13.94
16.94
12.26
16.93
12.16
15.03
15.51
16.06
15.03

K cd
(mag)
16.44
17.27
14.73
15.68
16.09
16.65
14.98
14.94
13.72
15.00
13.63
15.59
15.36
14.55
11.40
13.33
13.90
16.59
15.09
14.54
15.06
14.72
14.97
12.69
13.02
14.03
12.83
13.73
16.23
11.89
16.05
11.95
14.39
15.12
15.84
14.80
0534398−050800
0534399−050408

0534397−050306

0534393−050146

0534393−050046

0534384−051042
0534385−050419
0534385−050044
0534387−050405
0534388−050440
0534388−050236
0534388−051428

0534381−050305
0534381−050458
0534381−050517
0534383−050125

0534377−051429
0534379−050847
0534378−051332

0534368−050609

2MASS
counterpart

248
APPENDIX B. QUIRC SOURCES AND 2MASS COUNTERPART

ID
R.A.a
73 34:39.98
74 34:40.41
75 34:40.64
76 34:40.66
77 34:40.73
78 34:41.32
79 34:41.53
80 34:41.55
81 34:41.84
82 34:42.01
83 34:42.03
84 34:42.05
85 34:42.28
86 34:42.39
87 34:42.41
88 34:42.42
89 34:42.60
90 34:42.69
91 34:43.09
92 34:43.16
93 34:43.18
94 34:43.24
95 34:43.48
96 34:43.50
97 34:43.52
98 34:43.58
99 34:43.65
100 34:43.88
101
34:43.89
102 34:43.96
103 34:44.08
104
34:44.14
105
34:44.18
106 34:44.48
107 34:44.57
108
34:44.90
109 34:44.98
110 34:45.07
111 34:45.12(cont.)

decl.a−5:10:07.0−5:07:53.2−5:06:58.6−5:12:24.5−5:09:24.1−5:01:19.6−5:07:02.4−5:02:25.2−5:08:39.7−5:06:41.9−5:02:25.0−5:04:31.8−5:07:14.6−5:04:00.0−5:12:38.2−5:12:18.8−5:03:16.2−4:58:55.9−5:00:11.6−5:13:33.8−5:01:57.9−5:07:28.3−5:14:42.5−5:14:21.2−5:01:26.3−5:06:24.5−5:07:13.1−5:14:22.2−5:12:55.8−4:59:33.4−5:06:26.5−4:59:10.1−5:06:43.2−5:02:55.3−5:02:13.5−5:12:31.8−5:06:49.5−5:06:20.1−5:14:06.1

J bcd
9.11†
15.85
15.67
15.10
15.62
15.36
15.01
16.34
16.80
16.84
14.01
13.95
9.58†
17.78
13.22
10.00†
15.96
17.29
16.22
17.65
16.91
16.44
15.40
15.34
17.11
16.37
16.32
16.93
14.21
13.48
16.72
17.36
13.93
17.51
21.20
15.28
11.74
13.79
14.57

H bcd
8.96†
15.43
13.21
14.49
14.98
14.34
14.69
15.58
16.29
16.15
13.33
13.23
9.64†
16.83
12.40
9.18†
15.19
16.42
15.72
16.72
15.87
15.86
14.09
14.38
16.33
15.81
15.65
15.88
13.16
12.80
16.19
16.20
13.30
16.48
18.76
14.33
11.25
12.58
13.46

K cd
8.83†
15.21
11.87
14.20
14.66
14.03
14.29
15.37
16.04
15.81
13.09
12.52
9.58†
16.44
12.13
8.86†
15.00
15.67
15.43
16.31
15.66
15.77
13.84
14.12
16.06
15.53
15.27
15.80
12.89
12.58
15.55
15.70
13.12
16.23
16.66
13.75
10.75†
12.14
12.91
0534448−051231
0534449−050649
0534450−050620
0534451−051406

0534441−050643

0534438−051255
0534439−045933
0534440−050626

0534435−050624

0534434−051442
0534434−051421

0534430−050011

0534424−051238
0534424−051218
0534425−050316

0534420−050224
0534420−050431
0534422−050714

2MASS
0534399−051007
0534403−050753
0534406−050658
0534406−051224
0534407−050924
0534413−050119
0534415−050702
0534415−050225

ID
R.A.a
112
34:45.14
113
34:45.19
114
34:45.33
115
34:45.45
116
34:45.53
117
34:45.95
118
34:46.02
119
34:46.08120
34:46.35
121
34:46.60
122
34:46.63
123
34:46.79
124
34:46.82
125
34:46.91
126
34:46.94
127
34:47.03
128
34:47.08129
34:47.09130
34:47.68
131
34:47.68
132
34:47.85
133
34:47.96
134
34:48.25
135
34:48.26
136
34:48.28
137
34:48.29
138
34:48.42
139
34:48.49
140
34:48.51
141
34:48.77
142
34:48.98
143
34:49.17
144
34:49.18
145
34:49.22
146
34:49.35
147
34:49.37
148
34:49.49
149
34:49.58
150
34:49.59(cont.)

decl.a−5:00:05.9−5:10:47.6−5:00:50.0−5:02:07.9−5:10:16.0−5:04:14.3−5:08:58.1−5:13:11.6−5:01:22.8−5:04:46.6−5:10:40.4−5:04:26.8−4:59:10.9−5:06:46.3−4:59:13.1−5:08:12.4−5:00:22.3−5:08:45.6−4:59:16.3−4:59:33.3−5:00:18.7−5:04:54.9−5:10:39.0−5:03:30.3−5:09:00.8−5:07:13.5−5:05:01.4−5:01:52.3−5:07:11.0−5:02:46.8−5:06:56.9−4:56:01.0−5:01:38.1−5:04:38.1−5:11:53.5−4:59:38.2−5:11:34.8−5:04:59.6−5:11:18.0

J bcd
16.37
12.21
14.35
12.27
14.65
17.53
16.53
15.77
>21.62
15.75
12.05
16.85
12.31
17.30
12.13
17.18
16.68
16.62
>21.51
13.65
16.89
11.89
16.00
17.05
15.25
12.83
12.47
17.57
13.30
17.02
17.71
19.36
17.53
12.48
17.21
16.61
17.78
13.31
17.13

H bcd
15.48
11.43
13.53
11.58
13.99
16.73
15.63
14.96
>20.67
15.05
11.47
15.81
11.51
16.38
11.38
16.51
15.78
15.58
19.94
13.00
15.83
11.16
15.32
15.99
14.22
12.16
11.79
15.92
12.70
16.06
16.47
16.27
16.45
11.77
16.09
15.70
16.19
12.59
16.19

K cd
15.12
11.04
13.27
11.33
13.89
16.56
15.31
14.41
16.70
14.92
11.32
15.37
11.16
16.23
11.03
16.19
15.51
15.45
16.71
12.75
15.38
10.67†
15.27
15.89
13.93
12.02
11.64
15.67
12.51
15.57
15.94
14.88
15.85
11.58
15.70
15.35
15.51
12.29
16.01
0534495−050459

0534493−045937

0534492−050438

0534485−050710

0534482−050900
0534482−050713
0534484−050501

0534479−050455
0534482−051038

0534476−045933

0534470−050022

0534469−045912

0534465−050446
0534466−051040

0534460−050858

2MASS
0534451−050005
0534451−051047
0534453−050049
0534454−050207
0534455−051016

249

ID
R.A.a
151
34:49.69
152
34:49.73
153 34:50.04
154
34:50.04
155 34:50.11
156
34:50.15
157 34:50.15
158
34:50.27
159 34:50.32
160
34:50.51
161 34:50.56
162
34:50.66
163 34:50.73
164 34:51.15
165
34:51.15
166 34:51.31
167 34:51.41
168 34:51.43
169
34:51.43
170
34:51.73
171 34:51.77
172 34:51.82
173
34:52.08174
34:52.26
175 34:52.40
176 34:52.61
177 34:52.69
178 34:52.76
179 34:52.93
180
34:53.05
181 34:53.13
182 34:53.43
183 34:53.44
184 34:53.53
185
34:53.56
186
34:53.56
187 34:53.63
188 34:53.64
189 34:53.65(cont.)

decl.a−5:07:07.4−5:00:03.0−5:00:37.4−5:02:57.3−4:58:18.6−4:56:42.5−5:16:06.3−4:59:24.3−5:15:04.7−5:11:10.5−5:06:38.3−5:04:07.8−4:58:37.0−4:55:48.4−5:12:32.2−4:56:13.5−5:00:11.4−5:13:29.5−5:14:40.3−5:08:18.8−4:55:55.4−4:58:28.9−4:58:24.1−5:12:03.2−5:14:19.6−5:15:36.5−5:10:32.7−5:00:50.8−5:15:19.5−5:03:27.0−4:56:49.4−5:10:27.8−4:57:32.8−5:11:52.2−5:02:55.1−5:03:47.5−5:01:29.0−5:02:02.6−5:04:47.3

J bcd
17.62
15.27
17.73
17.62
17.16
>21.50
18.08
16.13
17.00
11.80
13.97
12.66
12.25
17.44
13.73
>21.24
13.20
12.86
19.83
16.44
15.88
>21.76
17.44
13.10
15.96
13.04
16.37
13.10
16.47
12.01
>21.49
12.14
13.38
15.73
18.17
17.97
14.32
14.91
17.23

H bcd
16.23
14.71
16.54
16.15
16.21
>20.55
16.58
15.20
15.84
11.21
13.46
11.88
11.21
15.28
12.80
19.75
12.46
12.19
17.94
15.34
13.67
>20.81
16.24
12.36
14.96
11.74
15.19
12.39
15.34
11.40
>20.54
11.51
12.52
14.47
16.64
16.68
13.71
13.84
15.87

K cd
15.83
14.55
16.05
15.56
15.95
16.55
15.66
14.97
15.23
11.09†
13.18
11.60
10.81†
14.48
12.41
15.07
12.20
11.94
16.40
15.01
12.68
17.72
15.82
12.17
14.67
11.18
14.92
12.16
14.64
10.73†
16.66
11.29
12.29
13.91
16.21
16.06
13.38
13.55
15.15
0534536−050129
0534536−050202

0534534−051027
0534534−045732

0534530−050327

0534526−051536
0534526−051032
0534527−050050

0534522−051203

0534517−050818
0534517−045555

0534514−050011
0534514−051329

0534511−051232

0534505−051110
0534505−050638
0534506−050407
0534507−045836

0534502−045924

0534497−050003

2MASS

ID
R.A.a
190
34:53.71
191
34:53.73
192
34:53.80
193
34:53.87
194
34:53.89
195
34:53.96
196
34:54.16
197
34:54.58
198
34:54.82
199
34:54.90
200
34:54.92
201
34:54.93
202
34:55.00
203
34:55.11
204
34:55.23
205
34:55.32
206
34:55.35
207
34:55.38
208
34:55.40
209
34:55.42
210
34:55.49
211
34:55.49
212
34:55.61
213
34:55.64
214
34:55.67
215
34:55.81
216
34:55.86
217
34:55.87
218
34:55.91
219
34:56.10
220
34:56.13
221
34:56.17
222
34:56.18
223
34:56.36
224
34:56.38
225
34:56.54
226
34:56.63
227
34:56.66
228
34:56.67(cont.)

decl.a−4:59:13.8−5:05:48.8−5:12:24.2−4:56:22.4−5:07:55.4−4:56:15.7−5:11:21.9−4:56:05.4−5:10:12.6−5:02:43.6−5:01:28.4−5:02:21.2−4:55:37.6−5:17:45.5−5:15:58.4−4:56:59.6−5:09:25.5−5:13:51.9−5:16:00.9−5:01:39.5−5:11:15.1−5:12:59.3−5:12:34.9−5:06:30.3−4:56:12.0−4:58:17.1−5:07:30.0−5:08:21.2−5:15:47.8−5:00:55.2−5:06:01.8−5:09:25.4−5:05:06.6−5:08:04.8−5:15:28.3−5:01:07.2−5:11:12.4−5:11:03.3−5:14:52.3

J bcd
17.92
13.25
16.58
12.43
16.98
17.30
18.74
12.17
16.77
17.07
18.00
12.13
>21.40>21.00
18.36
14.37
16.80
17.57
17.33
12.51
17.97
18.24
19.06
18.14
12.39
18.87
16.89
12.84
17.79
12.73
12.53
15.00
18.32
17.90
18.30
14.35
13.56
17.17
14.94

H bcd
16.74
12.61
15.98
11.42
15.72
16.14
16.88
11.15
16.42
16.02
16.94
11.52
17.64
15.65
15.43
13.70
15.62
16.27
14.97
11.71
16.48
16.79
16.89
16.82
11.10
17.40
15.81
11.96
16.53
11.94
11.93
14.08
17.51
16.21
15.76
13.54
12.53
15.50
13.83

K cd
16.23
12.39
15.45
10.99†
15.13
15.52
16.42
10.54†
15.40
15.16
16.22
11.25†
16.16
14.57
14.73
13.49
15.08
16.04
14.29
11.55
15.95
16.14
16.45
15.94
10.26†
16.07
15.31
11.74
16.54
11.74
11.64
13.76
16.73
15.85
15.13
13.10
12.04
15.00
13.25
0534566−051452

0534565−050107
0534566−051112

0534561−050055
0534561−050601
0534561−050925

0534558−050730
0534558−050821

0534556−045611

0534554−050139

0534553−045659

0534549−050220

0534545−045605

0534538−045622

0534537−050548

2MASS

250
APPENDIX B. QUIRC SOURCES AND 2MASS COUNTERPART

ID
R.A.a
229
34:56.72
230 34:56.77
231 34:56.78
232
34:56.82
233 34:56.95
234 34:57.07
235
34:57.16
236 34:57.18
237 34:57.20
238
34:57.31
239 34:57.32
240 34:57.38
241 34:57.46
242 34:57.61
243
34:57.63
244 34:57.68
245 34:57.71
246
34:57.89
247 34:58.03
248 34:58.03
249 34:58.05
250 34:58.15
251
34:58.19
252 34:58.19
253 34:58.21
254 34:58.24
255 34:58.49
256 34:58.69
257 34:58.69
258 34:58.83
259
34:58.84
260
34:58.93
261 34:58.93
262 34:59.08
263
34:59.21
264 34:59.31
265 34:59.32
266 34:59.43
267 34:59.67(cont.)

decl.a−5:13:56.9−5:09:58.5−5:10:43.8−5:11:33.0−4:54:36.0−5:00:55.9−5:01:35.5−5:07:16.8−5:08:23.9−5:02:50.8−5:04:00.2−5:14:33.5−4:56:45.5−4:54:33.3−5:06:25.4−5:12:29.7−4:57:20.0−5:08:42.7−5:06:25.9−5:16:01.9−5:17:37.5−5:07:12.4−5:09:27.5−5:11:53.7−5:00:13.2−4:54:04.3−5:07:48.2−5:12:21.6−5:12:26.1−5:15:35.7−5:17:01.1−5:13:45.4−5:16:13.3−4:57:34.0−5:17:39.9−5:05:30.0−5:06:06.9−4:57:37.1−5:02:54.4

J bcd
15.95
14.10
13.46
10.92†
18.24
18.23
17.63
16.06
12.08
18.42
18.59
13.44
14.40
>21.31
18.46
14.35
17.98
16.78
17.84
14.60
12.61
16.88
12.26
12.61
17.50
17.28
15.88
16.74
14.04
17.70
15.45
13.72
16.56
18.61
16.81
12.37
16.43
18.58
18.54

H bcd
14.89
12.99
12.57
10.19†
15.22
16.87
16.47
14.95
11.36
16.50
16.98
12.30
12.51
17.55
16.91
12.89
14.82
15.85
16.33
13.09
11.48
15.66
11.51
11.98
16.38
14.71
14.84
16.10
13.44
16.75
14.57
12.43
15.57
16.82
15.72
11.63
15.37
16.59
16.60

K cd
14.35
12.58
12.31
9.69†
13.64
16.20
16.15
14.55
11.01
15.68
16.58
11.81
11.63
16.12
15.81
12.34
12.83
15.67
15.51
12.29
11.08
15.18
11.16
11.71
16.37
13.71
14.39
15.76
13.14
15.95
13.53
11.86
14.35
16.43
15.21
11.24
14.94
15.83
15.66
0534593−050530
0534593−050606

0534589−051345

0534586−051226

0534582−045404
0534584−050748

0534581−050927
0534581−051153

0534580−051601
0534580−051737

0534579−050842

0534576−051229

0534573−051433
0534574−045645

0534571−050716
0534571−050823

0534567−050958
0534567−051043
0534568−051132

2MASS

ID
R.A.a
268
34:59.88
269
34:59.99
270
35:00.19271
35:00.24272
35:00.25
273
35:00.34274
35:00.40
275
35:00.41276
35:00.44277
35:00.64
278
35:00.67279
35:00.73
280
35:00.86281
35:00.87
282
35:00.91
283
35:01.05
284
35:01.30
285
35:01.32
286
35:01.39
287
35:01.43
288
35:01.50
289
35:01.63290
35:01.93291
35:02.10292
35:02.18
293
35:02.38294
35:02.64
295
35:02.64
296
35:02.66
297
35:02.67
298
35:02.73
299
35:02.75
300
35:02.89
301
35:02.90302
35:02.99
303
35:03.04
304
35:03.07305
35:03.12306
35:03.24(cont.)

decl.a−4:55:27.1−5:10:41.0−5:00:09.4−5:15:58.9−4:56:08.8−5:00:59.6−5:09:44.0−5:09:54.5−5:15:21.7−4:58:53.5−5:05:08.6−5:11:27.6−5:09:39.1−5:09:16.0−5:05:40.1−5:05:33.5−5:06:32.9−4:55:57.0−4:56:32.6−5:09:32.7−5:11:04.1−4:56:46.2−5:00:43.3−5:15:37.5−5:04:38.4−5:15:47.9−4:54:17.3−5:09:59.1−4:56:42.8−4:58:18.3−5:08:53.9−5:00:03.0−5:03:03.7−4:54:30.2−4:57:04.0−4:59:59.9−5:13:54.4−5:09:17.1−5:17:53.1

J bcd
17.03
17.01
17.99
14.06
14.34
19.74
13.72
16.98
18.69
15.90
10.07†
16.60
12.99
17.51
15.84
15.50
17.06
14.34
16.47
12.17
13.77
18.78
14.50
12.69
13.77
9.32†
16.84
15.53
18.07
19.53
18.38
12.24
15.82
20.83
14.05
12.57
13.32
13.14
12.89

H bcd
13.89
15.79
16.78
12.81
13.12
17.68
13.01
16.25
16.69
15.10
9.95†
14.95
12.28
16.59
15.25
14.90
16.08
13.25
15.62
11.48
12.69
16.41
13.72
11.93
12.99
8.32†
14.89
14.44
16.37
18.16
16.93
11.18
15.06
16.27
13.33
11.85
11.84
12.28
12.44

K cd
12.46
15.18
16.57
12.19
12.57
16.81
12.72
15.78
16.01
14.75
9.89†
14.48
12.07
16.63
14.94
14.55
15.75
12.82
15.11
11.24
12.18
15.23
13.52
11.77
12.65
7.91†
13.89
14.07
15.06
16.27
16.09
10.64†
14.76
13.64
13.16
11.66
11.07
12.05
11.51
0535029−045703
0535030−045959
0535030−051354
0535031−050917
0535032−051753

0535027−050002
0535028−050303

0535019−050043
0535020−051537
0535021−050438
0535023−051547
0535026−045417
0535026−050959

0535013−045557
0535013−045632
0535014−050932
0535014−051104

0535009−050540
0535010−050533

0535008−050938

0535006−045853
0535006−050508

0535003−050944

0535002−051558
0535002−045608

2MASS
0534598−045527

251

ID
R.A.a
307
35:03.25
308 35:03.34
309 35:03.35
310 35:03.37
311 35:03.40
312 35:03.40
313
35:03.59
314 35:03.65
315
35:03.85316
35:04.08
317 35:04.20
318 35:04.29
319
35:04.30
320
35:04.38
321 35:04.38
322
35:04.40
323 35:04.40
324
35:04.60
325 35:04.62
326
35:04.63
327 35:04.64
328 35:04.70
329
35:04.78
330 35:05.10
331
35:05.20
332
35:05.21333
35:05.45334
35:05.48
335
35:05.61
336 35:05.68
337
35:05.68
338 35:05.70
339 35:05.74
340 35:05.78
341 35:05.88
342 35:06.06
343
35:06.10
344 35:06.19
345
35:06.34(cont.)

decl.a−5:17:26.2−5:16:22.7−4:56:43.0−5:08:53.8−5:05:40.3−5:16:45.1−5:16:00.4−5:13:10.4−5:07:49.0−5:17:42.8−5:15:21.4−5:13:13.9−5:08:12.6−5:01:15.4−5:08:16.7−4:57:15.4−5:07:35.6−4:56:45.4−4:58:29.0−5:09:55.7−4:54:02.5−5:01:50.9−5:17:41.9−4:53:51.4−5:14:50.2−5:03:39.8−4:57:05.5−4:54:34.6−5:11:50.5−4:58:53.9−5:02:40.1−4:58:33.4−5:11:35.0−4:55:36.2−5:08:38.2−5:03:19.0−5:14:24.9−5:12:15.8−4:58:41.6

J bcd
15.11
14.02
12.36
13.41
9.14†
19.92
14.38
15.17
16.96
17.18
13.70
17.78
8.19†
16.24
<10.0514.73
14.81>21.87
13.43
11.32
15.85
17.50
11.49
18.10
8.23†
19.48
20.56
19.85
12.90
11.99
17.54
15.95
12.94
19.76
15.06
17.19
13.28
8.09†
14.08

H bcd
13.82
12.38
11.59
12.09
8.95†
18.68
13.40
13.39
15.83
15.47
12.64
17.15
7.52†
14.48
<10.01
13.80
13.67>20.9312.10
10.74†
14.30
16.04
10.11†
16.05
7.71†
17.22
16.77
18.29
11.46
11.30
15.96
13.51
11.46
17.02
14.00
15.81
12.14
8.22†
13.46

K cd
12.80
11.56
11.34
11.66
8.90†
16.13
12.87
12.60
15.52
14.68
12.35
15.34
7.34†
13.68
<9.56
13.43
13.09
16.99
11.01†
10.45†
13.56
16.11
9.34†
14.91
7.38†
16.26
14.57
16.83
10.86†
11.04
15.27
12.46
10.83†
15.38
13.46
15.23
11.50
8.21†
13.27
0535061−051425
0535061−051216
0535063−045841

0535058−050838

0535056−045833
0535057−051135

0535056−051150
0535056−045853

0535051−051450

0535047−051742

0535046−045829
0535046−050955
0535046−045402

0535044−045715

0535042−050812
0535043−050115

0535042−051521

0535035−051600
0535036−051310

0535033−051622
0535033−045643
0535033−050853
0535034−050540

2MASS

ID
R.A.a
346
35:06.37347
35:06.50
348
35:06.72
349
35:06.73
350
35:06.83351
35:06.86352
35:06.88353
35:06.97354
35:07.02355
35:07.04356
35:07.13357
35:07.16
358
35:07.40
359
35:07.54360
35:07.75
361
35:07.79362
35:07.83
363
35:07.85364
35:07.88
365
35:08.23366
35:08.37367
35:08.38368
35:08.45369
35:08.48
370
35:08.60
371
35:08.64372
35:08.67373
35:08.68374
35:08.69375
35:08.69376
35:08.75
377
35:08.83
378
35:08.95379
35:08.96
380
35:09.09381
35:09.14382
35:09.15
383
35:09.19384
35:09.24(cont.)

decl.a−5:03:02.5−5:17:22.2−5:11:45.3−5:16:46.4−5:10:38.4−5:11:50.0−5:11:33.0−4:57:04.2−5:01:34.8−4:54:56.7−4:55:50.7−4:55:43.2−5:07:38.0−5:11:14.5−5:04:55.4−5:01:19.3−5:02:43.7−5:10:06.7−5:17:05.4−4:54:10.2−5:16:20.5−5:16:25.0−5:07:13.5−5:03:48.5−5:09:30.3−5:16:47.6−5:16:13.3−4:59:33.2−4:54:41.2−5:17:30.6−5:04:40.8−5:17:05.9−5:05:52.5−5:10:25.8−5:10:09.7−5:16:44.2−5:06:47.1−5:16:51.7−5:10:22.6

J bcd
16.23
14.39
13.91
16.89
12.56
15.84
17.78
18.48
17.68
12.80
14.66
19.38
17.37
12.31
17.43
16.23
17.37
16.79
13.99
14.57
14.19
>21.73
14.37
18.74
17.51
14.83
16.30
19.66
17.32
>20.98
12.81
15.54
9.05†
14.54
17.39
16.43
11.24
14.62
18.20

H bcd
14.80
12.66
12.43
15.31
11.81
14.91
15.82
15.25
16.86
11.95
13.18
17.23
15.56
11.32
15.87
15.27
15.91
15.72
12.98
11.91
13.21
>20.78
13.13
16.64
15.57
13.64
13.73
17.98
15.82
16.59
11.61
13.94
7.91†
13.83
15.81
14.36
10.57†
13.31
16.59

K cd
14.28
11.67
11.75
14.13
11.61
14.23
14.77
13.59
16.16
11.84
12.61
15.15
14.62
10.70†
15.64
14.80
15.64
15.21
12.14
10.28†
12.49
17.45
12.71
15.92
14.78
12.52
11.79
16.78
14.83
14.18
11.44
12.59
7.41†
13.74
15.31
12.63
10.33†
12.14
16.13
0535091−050647

0535089−050552
0535089−051025

0535087−050440

0535084−050713

0535082−045410

0535077−050119

0535075−051114

0535070−045456
0535071−045550

0535068−051038

0535067−051145

2MASS
0535063−050302

252
APPENDIX B. QUIRC SOURCES AND 2MASS COUNTERPART

ID
R.A.a
385
35:09.28
386 35:09.38
387 35:09.45
388 35:09.46
389 35:09.49
390
35:09.54391
35:09.82392
35:09.83
393
35:09.88
394 35:09.96
395 35:10.01
396 35:10.05
397
35:10.09398
35:10.11
399
35:10.28
400 35:10.30
401
35:10.38
402 35:10.53
403
35:10.73
404 35:10.79
405 35:10.83
406 35:10.85
407
35:10.97
408 35:11.00
409
35:11.11
410
35:11.12
411 35:11.16
412
35:11.18
413
35:11.23
414 35:11.24
415
35:11.34
416 35:11.41
417
35:11.45
418 35:11.50
419 35:11.63
420
35:11.76
421 35:11.79
422 35:11.81
423 35:11.87(cont.)

decl.a−5:16:55.7−4:55:13.6−5:16:53.3−4:57:11.7−4:59:41.4−5:14:45.8−4:53:52.6−4:56:19.4−4:58:49.5−5:14:50.1−5:14:57.3−5:16:22.9−5:17:06.8−5:16:16.9−5:03:05.0−5:17:19.9−4:54:41.2−4:58:46.0−5:08:16.8−5:10:34.4−5:17:33.2−4:55:42.6−4:56:39.7−5:15:21.8−5:16:01.8−4:54:14.9−4:55:28.0−4:55:38.1−5:17:20.8−5:17:42.3−5:14:01.6−5:17:46.5−5:05:16.2−5:17:57.3−5:16:57.6−5:16:52.0−4:54:21.5−5:03:30.2−5:01:56.0

J bcd
13.82
>21.53
14.19
13.92
12.94
>21.13
17.07
19.33
16.45
14.42
16.57
17.50
14.68
17.08
16.85
21.61
15.93
>21.08
16.11
12.46
15.09
17.33
16.85
15.99
16.30
20.13
18.16
17.86
12.30
16.28
13.80
15.12
16.20
15.42
9.56†
14.16
16.06
14.54
17.30

H bcd
12.76
>20.58
13.14
13.11
12.24
15.94
14.95
17.22
13.22
13.50
15.74
15.35
12.98
15.06
14.99
16.60
15.26
13.84
14.32
11.11
13.40
15.75
14.71
13.39
14.38
17.13
15.46
15.89
<10.55
14.89
12.80
13.23
14.94
12.56
8.94†
13.20
14.37
13.07
15.91

K cd
11.96
16.21
12.15
12.51
11.85
14.78
13.66
15.26
11.51
12.99
15.00
14.58
11.84
14.06
14.16
14.72
15.31
<10.45
13.14
10.41†
11.99
14.36
13.33
11.13
13.16
16.00
14.00
14.60
<9.22
13.96
12.37
11.72
14.28
<10.52
8.70†
12.99
13.56
12.51
14.93
0535118−045421
0535118−050330

0535116−051657

0535114−050516

0535113−051401

0535109−045639

0535107−051034

0535103−045441

0535099−051450

0535094−045711
0535094−045941

2MASS

ID
R.A.a
424
35:11.87425
35:11.89426
35:12.05427
35:12.13
428
35:12.17429
35:12.30
430
35:12.31
431
35:12.51432
35:12.52433
35:12.55434
35:12.57
435
35:12.69
436
35:12.69
437
35:12.69
438
35:12.70
439
35:12.70
440
35:12.72
441
35:12.73
442
35:12.74
443
35:12.81444
35:12.82445
35:12.87446
35:12.95
447
35:12.97448
35:13.03449
35:13.10
450
35:13.11451
35:13.19452
35:13.32
453
35:13.41454
35:13.47455
35:13.48
456
35:13.52457
35:13.53458
35:13.59459
35:13.64460
35:13.86461
35:13.92462
35:13.92(cont.)

decl.a−5:17:25.9−5:00:00.9−5:14:14.7−5:03:48.4−5:14:30.1−5:04:26.4−5:17:50.0−5:16:26.3−4:57:13.7−4:56:01.9−5:16:33.2−4:54:02.6−4:56:00.7−5:02:26.5−5:12:00.7−5:12:28.8−5:16:13.4−5:15:43.2−5:16:52.7−5:01:46.3−5:15:23.9−5:15:48.7−5:02:08.7−5:07:47.5−5:00:26.1−4:55:52.3−5:15:26.3−5:17:30.6−5:09:19.5−4:54:21.2−5:17:10.5−5:05:51.3−5:17:31.4−5:17:17.6−5:17:45.9−5:14:22.2−4:58:03.5−4:53:58.4−5:18:53.2

J bcd
13.55
>21.66
13.93
18.26
17.18
18.51
15.74
>21.04
15.07
17.49
13.87
16.76
17.45
18.55
14.17
16.43
12.60
14.67
11.37
13.92
11.65
14.82
14.42
>21.67>20.99
12.98
13.27
15.22
12.06
18.16
11.49
19.09
13.14
13.24
17.34
15.74
15.58
>22.11
13.57

H bcd
11.89
>20.71
13.47
16.44
15.93
16.27
13.99
15.79
13.13
14.20
11.40
14.12
14.20
16.65
13.53
14.95
11.91
14.05
10.18†
13.27
10.72†
14.35
13.76
19.58
16.97
11.00
12.60
12.86
11.35
17.42
10.39†
17.51
11.45
12.09
14.23
15.02
13.12
>21.16
12.89

K cd
11.81†
16.69
13.41
15.59
15.10
14.99
12.49
13.45
12.35
12.28
9.90†
12.24
12.24
15.69
13.20
13.78
11.67
13.33
9.62†
13.01
10.39†
13.71
13.42
17.14
14.43
9.29†
12.27
<10.88
11.19
17.41
9.93†
16.51
11.16†
11.61
11.40
15.15
11.93
16.97
11.55†
0535139−051853

0535136−051421
0535138−045803

0535135−051731
0535135−051717

0535134−051710

0535133−050919

0535131−045552

0535129−050208

0535127−051652
0535128−050146
0535128−051524

0535127−051613

0535127−051200

0535125−051633

0535125−045713

0535120−051414

2MASS
0535118−051725

253

ID
R.A.a
463
35:13.96464
35:14.04465
35:14.06466
35:14.19
467
35:14.22468
35:14.29
469
35:14.29
470 35:14.38
471
35:14.46
472 35:14.47
473 35:14.47
474
35:14.47
475 35:14.64
476 35:14.64
477 35:14.65
478 35:14.68
479 35:14.68
480 35:14.69
481 35:14.70
482 35:14.70
483
35:14.73
484
35:14.74
485 35:14.77
486 35:14.82
487 35:14.86
488
35:14.88489
35:14.89
490 35:14.91
491
35:14.97492
35:14.99493
35:15.00
494 35:15.05
495
35:15.05
496
35:15.07
497 35:15.08
498
35:15.26
499 35:15.29
500
35:15.33
501 35:15.33(cont.)

decl.a−5:18:44.9−5:18:48.9−5:04:06.1−5:02:01.7−5:14:27.8−5:13:40.7−5:18:21.2−4:55:22.0−4:55:24.7−5:17:25.6−5:17:40.5−5:18:24.8−5:02:25.0−5:16:46.3−5:06:25.3−5:03:12.7−5:08:52.1−5:06:22.3−5:16:52.4−5:18:43.3−5:02:27.9−5:14:00.5−5:14:15.1−5:18:30.6−5:06:48.9−5:17:53.7−5:07:47.7−5:03:21.5−4:56:08.3−4:56:04.6−5:16:49.6−5:00:08.2−5:16:39.5−5:06:53.8−4:58:08.6−5:00:33.4−5:15:48.2−5:13:15.5−5:13:38.2

J bcd
17.30
14.74
20.01
18.49
14.86
16.51
15.92
12.86
13.08
12.36
17.03
15.56
12.82
13.04
14.38
12.59
12.80
16.54
>21.78
16.54
13.14
15.62
>21.52
16.91
16.90>21.9313.91
18.22>20.86>21.05
17.22
17.21
18.01
15.83
17.57
13.45
14.39
>21.70
13.49

H bcd
14.14
12.62
17.14
16.75
12.95
14.52
13.89
11.75
11.87
11.19†
16.74
12.67
11.76
12.18
13.25
11.74
12.21
15.36
>20.83
12.58
11.86
13.84
17.51
13.79
14.54
17.99
13.20
17.33
15.86
15.12
17.26
15.86
14.75
13.59
15.96
12.73
13.62
>20.75
12.61

K cd
12.54
11.41
16.13
16.20
11.82
13.22
12.65
11.28
11.28
10.73†
17.11
11.40
11.26
11.70
12.72
11.59
12.06
14.75
15.54
11.31
11.26
12.81
16.32
12.84
13.39
17.32
12.77
16.67
13.61
13.22
15.28
14.10
13.19
12.47
14.84
12.52
13.06
16.21
12.46
0535152−050033

0535150−050653

0535148−050747

0535147−051400

0535146−051646
0535146−050625
0535146−050312
0535146−050852

0535144−051725

0535143−045522

0535142−051427
0535143−051340

2MASS

ID
R.A.a
502
35:15.34
503
35:15.36504
35:15.37
505
35:15.44506
35:15.46507
35:15.47
508
35:15.47
509
35:15.53
510
35:15.54511
35:15.55
512
35:15.57
513
35:15.59
514
35:15.60
515
35:15.61
516
35:15.62517
35:15.64
518
35:15.65
519
35:15.69
520
35:15.78
521
35:15.79
522
35:15.80
523
35:15.82
524
35:15.84
525
35:15.86526
35:15.89527
35:15.93
528
35:15.96529
35:15.97
530
35:16.14531
35:16.17532
35:16.17
533
35:16.19534
35:16.20
535
35:16.21536
35:16.29
537
35:16.31
538
35:16.34
539
35:16.35
540
35:16.37(cont.)

decl.a−4:57:46.1−5:02:50.6−5:19:02.1−5:16:00.3−5:17:39.1−5:00:11.4−5:01:12.5−5:17:36.5−5:08:58.9−5:01:43.8−5:07:28.6−5:09:51.2−4:59:27.9−5:05:50.6−5:09:31.9−4:57:13.9−5:06:12.5−5:17:47.3−5:15:27.6−5:16:42.3−5:12:26.4−5:03:26.1−5:00:36.3−4:57:11.3−5:06:54.3−5:06:13.6−5:14:59.1−5:16:57.6−5:15:48.4−5:00:02.5−5:09:19.1−5:14:13.3−5:19:02.9−5:19:06.8−4:57:36.0−5:17:44.3−5:15:38.1−5:04:36.4−5:18:09.0

J bcd
16.76
17.91
12.68
17.74
12.36
18.15
14.47
12.37
15.96
13.73
19.08
13.41
14.60
17.46
13.93
13.30
16.51
12.63
20.48
18.60
18.38
13.84
12.27
13.99
18.88
16.80
11.58
12.57
14.76
16.16
12.94
16.81
15.75
15.89
19.85
13.96
12.03
14.85
15.50

H bcd
14.82
15.53
11.36
16.47
<10.7317.32
13.70<10.83
15.32
12.56
18.06
12.23
12.70
14.93
13.35
12.40
15.62
<10.65
18.42
17.62
15.20
13.11
11.80
13.13
17.06
15.91
11.15
11.55
14.40
13.57
12.27
14.88
13.18
13.35
16.59
12.21
11.27
14.13
12.70

K cd
13.82
14.16
11.07
14.78
<9.51
15.60
13.41
<9.66
15.19
12.05
16.34
11.60
11.47
13.11
13.11
12.15
13.29
<9.50
17.29
15.42
13.88
12.72
11.75
12.77
16.37
13.75
<10.72
11.07
14.12
11.77
12.11
13.80
11.98
12.37
15.31
11.03
<10.7413.82
11.49
0535163−050436

0535161−050919

0535158−050326
0535158−050036
0535158−045711

0535156−050931
0535156−045713

0535155−050951
0535156−045927

0535155−050858
0535155−050143

0535154−050112

2MASS

254
APPENDIX B. QUIRC SOURCES AND 2MASS COUNTERPART

ID
R.A.a
541
35:16.41542
35:16.42543
35:16.44
544 35:16.48
545
35:16.49
546 35:16.51
547
35:16.51548
35:16.61
549
35:16.63
550 35:16.74
551 35:16.78
552 35:16.79
553 35:16.80
554
35:16.80
555
35:16.80
556 35:16.86
557 35:16.89
558
35:16.91
559 35:16.94
560
35:17.01561
35:17.02562
35:17.07
563 35:17.12
564
35:17.13565
35:17.14
566 35:17.15
567 35:17.15
568
35:17.15
569
35:17.38570
35:17.42571
35:17.42
572 35:17.43
573 35:17.45
574 35:17.50
575 35:17.50
576
35:17.51
577 35:17.54
578 35:17.56
579
35:17.57(cont.)

decl.a−4:58:02.0−4:56:53.1−4:58:07.0−5:06:00.6−4:57:17.4−5:03:30.4−5:17:47.3−5:16:20.6−5:17:23.5−5:18:44.8−5:17:16.9−5:07:27.3−5:14:47.4−5:16:53.3−5:19:01.1−5:07:47.8−5:15:09.2−5:17:03.0−5:18:41.0−5:17:32.1−5:15:44.3−5:17:29.0−5:19:00.7−5:18:13.7−4:58:06.1−4:57:47.1−5:12:39.4−5:18:06.5−5:12:29.6−4:59:57.0−5:05:00.9−5:17:12.5−5:16:57.0−5:09:49.1−5:16:50.0−5:18:22.5−5:17:40.1−5:16:13.0−5:19:28.9

J bcd
13.25
19.40
13.41
15.32
18.77
12.42
14.55
15.72
13.12
15.29
13.43
14.89
15.61
13.60
13.95
13.77
16.05
13.40
15.50
14.92
12.50
15.03
14.91
>21.68
16.48
15.14
13.51
>21.6713.70
17.47>21.57
16.56
14.42
13.34
19.02
16.02
<10.79
12.56
13.53

H bcd
12.54
17.61
12.59
14.60
16.53
11.72
12.73
14.19
11.10
13.38
12.47
14.41
14.58
12.79
11.40
12.81
14.15
11.73
12.81
13.67
11.64
13.79
12.38
>20.73
14.91
14.47
12.89
18.80
13.08
14.64
19.73
15.63
13.61
12.70
18.79
12.73
<9.46
11.22
11.07

K cd
12.35
16.45
12.34
12.86
15.41
11.35
11.65
13.36
<9.77
11.64
11.91
14.01
13.92
12.42
<10.0312.32
12.96<10.80
11.38
13.34
11.01
13.87
<10.87
14.59
14.06
14.17
12.78
13.47
12.93
12.89
17.19
15.02
13.12
12.47
16.76
<10.90<8.53<10.60<10.160535174−050949

0535171−045806
0535171−045747

0535168−050747

0535167−050727

0535164−050330

0535164−045807

2MASS
0535164−045802

ID
R.A.a
580
35:17.61
581
35:17.62582
35:17.67583
35:17.71584
35:17.73
585
35:17.79586
35:17.82
587
35:17.83
588
35:17.91589
35:17.91590
35:17.92591
35:17.98
592
35:17.98593
35:17.99594
35:18.01595
35:18.11596
35:18.19
597
35:18.21598
35:18.21599
35:18.21600
35:18.22
601
35:18.24
602
35:18.24
603
35:18.30
604
35:18.33
605
35:18.35606
35:18.37
607
35:18.38
608
35:18.44609
35:18.45
610
35:18.46611
35:18.47
612
35:18.52613
35:18.55
614
35:18.60
615
35:18.60
616
35:18.60
617
35:18.62618
35:18.62(cont.)

decl.a−5:18:32.6−5:16:41.1−5:16:55.2−5:03:08.9−5:00:30.9−5:16:15.7−5:19:28.1−4:55:17.2−5:17:56.0−5:18:35.2−5:15:32.9−4:57:59.7−5:16:45.1−5:15:38.7−5:16:13.6−5:15:46.1−5:17:53.9−5:03:54.5−5:16:33.9−5:17:22.0−5:15:06.1−5:13:06.9−5:17:44.9−5:08:04.8−5:00:32.9−5:13:16.7−5:19:17.5−5:15:01.5−5:07:14.5−5:06:45.9−5:16:37.7−5:08:30.7−5:13:38.4−5:18:20.5−4:55:11.0−4:59:42.3−5:16:35.1−5:06:47.3−5:13:27.5

J bcd
15.01
16.84
17.10
20.58
15.07
11.94
14.11
16.98
14.61
13.54
11.50
18.33
13.07
13.06
11.18
13.37
15.01
9.26†
12.76
15.69
17.15
11.36
13.68
17.02
18.02
14.53
15.32
>21.86>21.2819.93<10.36
13.79
11.34
12.80
17.52
13.86
<10.54
20.70
16.73

H bcd
12.13
16.39
16.17
17.33
12.86
<10.65
11.75
14.51
12.86
<10.59<10.76
16.27
11.70
12.39
<10.00
12.69
13.54
9.26†
11.97
13.41
16.69
<10.34
11.61
14.58
14.57
13.30
13.72
>20.91
17.44
18.01
<9.89
13.13
<10.40
11.36
15.58
13.22
<9.97
16.47
14.53

K cd
<10.92
16.31
15.64
15.93
11.55
<9.97
<10.82
13.14
11.84
<9.54
<10.18
15.40
11.04
11.86
<9.37
12.39
13.04
9.21†
11.70
11.57
16.08
<9.78
<10.12
13.24<10.72
12.67
12.26
16.27
15.94
15.45
<9.57
12.97
<9.61
11.10
14.09
12.96
<9.57
14.15
13.25
0535186−045942

0535184−050830

0535182−050354

0535177−050031

2MASS

255

ID
R.A.a
619
35:18.64620
35:18.69
621 35:18.71
622 35:18.75
623 35:18.82
624
35:18.83
625
35:18.86626
35:18.90
627 35:18.92
628 35:18.95
629
35:18.97
630 35:19.10
631 35:19.20
632
35:19.25
633 35:19.25
634
35:19.28
635
35:19.31
636 35:19.32
637 35:19.32
638
35:19.33
639
35:19.38
640 35:19.48
641
35:19.52
642 35:19.58
643 35:19.66
644 35:19.66
645 35:19.67
646 35:19.74
647
35:19.75
648 35:19.80
649
35:19.80
650
35:19.82651
35:19.84
652 35:19.98
653 35:20.00
654
35:20.03
655 35:20.12
656
35:20.20
657
35:20.24(cont.)

decl.a−5:18:35.1−5:17:43.1−5:15:18.1−5:18:02.2−5:17:29.0−5:17:20.9−5:14:45.6−5:19:02.9−5:16:13.9−5:12:31.3−5:17:51.6−4:54:07.8−5:18:39.1−5:16:58.6−5:17:31.6−5:19:11.9−5:16:44.6−4:55:44.9−5:16:10.0−5:19:03.7−5:17:19.2−5:16:08.2−5:08:58.1−5:17:03.1−5:02:28.8−5:13:26.5−5:03:34.5−5:19:30.1−5:04:54.3−4:57:06.7−5:14:05.4−5:15:35.4−5:15:09.0−5:01:02.4−5:18:46.6−5:12:50.5−4:58:40.2−5:15:59.5−5:13:16.2

J bcd
14.10
16.17
14.30
12.86
11.37
16.09
12.48
15.06
11.66
17.89
16.50
13.70
15.89
15.89
15.58
16.94
12.87
15.67
14.48
15.49
14.59
13.93
19.28
13.55
14.54
13.61
18.72
>21.0318.13>21.06
13.52
17.65
13.00
>21.05
13.91
13.87
19.20
14.55
9.89†

H bcd
12.05
14.42
13.67
<10.95
<9.68
14.46
11.65
12.91
11.36
16.33
14.60
13.03
14.38
14.59
13.24
13.47
12.03
12.87
13.97
13.24
13.53
13.26
18.18
11.31
13.82
11.55
16.57
13.23
>20.17
16.83
13.10
14.95
11.43
18.28
12.04
11.96
16.74
12.94
7.86†

K cd
11.26
13.27
12.97
<10.00
<8.35
13.11
11.27
11.58
11.27
15.64
13.01
12.97
13.63
13.71
11.43
12.02
11.46
10.25†
13.66
12.12
12.51
12.77
15.59
10.06†
13.50
10.24†
15.30
11.27
13.94
14.86
12.68
12.35
10.26†
14.20
12.09
11.17
16.25
12.26
6.49†
0535201−051315

0535200−051250

0535198−051508

0535197−051405

0535195−051703
0535196−050228
0535196−051326

0535193−051644
0535193−045545

0535191−045407

2MASS

ID
R.A.a
658
35:20.25
659
35:20.25
660
35:20.36
661
35:20.42662
35:20.44
663
35:20.45
664
35:20.62665
35:20.67
666
35:20.68
667
35:20.74
668
35:20.76
669
35:20.77670
35:20.78
671
35:20.82
672
35:20.83
673
35:20.86674
35:20.99675
35:21.07676
35:21.09677
35:21.15
678
35:21.17
679
35:21.22680
35:21.28
681
35:21.32
682
35:21.32
683
35:21.38
684
35:21.41
685
35:21.45
686
35:21.47
687
35:21.47
688
35:21.50
689
35:21.52690
35:21.59
691
35:21.60
692
35:21.63
693
35:21.65
694
35:21.67
695
35:21.69
696
35:21.74(cont.)

decl.a−5:12:11.2−5:13:59.6−5:02:26.4−5:17:14.6−5:01:15.1−5:06:38.0−5:03:00.7−5:09:02.9−5:01:54.2−5:19:26.6−5:15:49.4−4:58:34.0−5:13:23.4−4:57:16.9−5:02:57.7−4:56:53.0−5:16:37.7−5:01:16.6−5:19:16.3−5:06:32.4−5:18:21.4−5:06:47.8−5:09:16.2−4:58:35.0−5:12:12.8−5:12:44.4−5:09:42.3−4:57:18.8−5:09:03.7−5:17:11.0−5:01:15.9−5:01:53.9−5:09:38.9−5:09:49.7−5:15:17.2−5:17:19.4−5:17:17.0−4:56:48.7−5:17:40.2

J bcd
14.74
12.24
12.39
11.99
18.43
>21.18
18.44
14.19
13.16
15.93
9.90†
12.39
15.11
16.28
19.49
>21.3012.02
16.87>21.78>21.23
12.85>21.15
8.38†
15.41
8.71†
15.91
13.74
20.51
12.27
>21.46
15.48
18.49
13.75
13.01
17.42
13.26
13.22
13.65
>21.20H bcd
14.04
10.75†
11.57
11.21†
17.32
17.87
14.47
13.17
12.35
14.66
8.68†
11.34
14.03
13.91
16.28
18.48
11.36
16.34
>20.83
18.56
11.97>20.20
7.84†
14.13
8.11†
15.20
12.89
17.02
11.32
>20.51
14.82
15.06
12.85
12.03
14.81
11.82
11.83
12.94
>20.25

K cd
14.12
9.88†
11.28
10.43†
15.98
15.62
11.94
12.70
12.20
11.78
8.08†
10.72†
13.40
12.74
13.60
15.16
11.19
14.12
15.56
15.31
11.57
15.39
7.31†
13.62
7.90†
14.63
12.57
15.77
<10.91
14.56
12.37
13.06
12.56
11.75
13.55
10.78†<10.8312.80
14.16
0535216−051718

0535215−050938
0535215−050949

0535213−050942

0535213−051212

0535212−050916

0535211−051821

0535210−051637

0535208−045717

0535207−051549
0535207−045834

0535206−050902
0535206−050154

0535202−051359
0535203−050226
0535204−051714

2MASS

256
APPENDIX B. QUIRC SOURCES AND 2MASS COUNTERPART

ID
R.A.a
697
35:21.76
698
35:21.76
699 35:21.77
700
35:21.85
701
35:21.88702
35:21.88703
35:21.88704
35:21.90705
35:21.91
706 35:21.94
707
35:21.94
708 35:21.94
709 35:21.95
710 35:22.08
711
35:22.08
712 35:22.13
713 35:22.23
714
35:22.25
715
35:22.26
716 35:22.37
717 35:22.37
718
35:22.39
719
35:22.42
720
35:22.46
721 35:22.57
722 35:22.58
723
35:22.60
724 35:22.63
725
35:22.67
726 35:22.71
727 35:22.75
728
35:22.89729
35:22.93
730 35:22.99
731 35:23.01
732
35:23.03
733 35:23.07
734 35:23.08
735
35:23.13(cont.)

decl.a−5:06:32.8−5:17:27.8−5:09:45.3−4:55:21.8−4:54:07.6−4:59:19.7−5:07:01.9−5:18:12.0−5:15:01.2−4:57:09.1−5:08:03.7−5:17:04.4−5:14:27.7−5:00:14.1−5:12:22.6−5:18:57.6−4:53:57.3−5:00:39.0−5:18:08.8−5:07:39.2−5:08:17.9−5:17:32.9−5:08:05.2−5:09:11.1−5:08:00.7−4:59:05.3−5:13:28.4−5:14:11.3−5:15:08.6−5:16:14.0−5:18:38.1−4:59:09.4−5:13:40.0−5:15:21.8−5:17:45.2−5:14:39.5−5:11:50.3−5:00:36.4−5:13:43.6

J bcd>21.18>21.32
19.37
20.53
11.91
15.35
11.27
17.22
12.78
18.35
13.05
12.19
11.79
20.75
17.36
>21.67
16.59
18.22
13.20
14.47
14.67
14.55
10.97†
11.44
11.26†
17.46
14.33
11.69
13.38
13.21
>21.25
14.61
14.10
16.43
>21.07>21.75
15.88
16.48
13.02

H bcd
17.30
>20.37
17.65
19.61
11.31
13.86
10.00†
16.66
11.85
15.70
12.03
11.81
11.36
17.25
16.69
>20.72
15.50
17.03
12.49
12.05
13.72
12.98
9.51†
11.12
9.78†
16.02
13.64
11.19
12.63
12.19
16.67
13.69
12.52
16.44
14.04
20.73
14.27
13.89
11.33

K cd
14.77
15.58
16.23
17.31
<10.68
13.01
9.40†
14.62
11.49
14.35
11.58
11.65
11.31
16.13
15.15
14.17
15.44
14.99
11.98
10.46†
13.52
12.01
8.59†
10.62†
9.21†
15.39
13.37
10.24†
12.35
11.82
12.80
13.12
11.66
13.73
11.63
16.14
13.20
12.45
10.49†
0535231−051343

0535229−051339

0535226−051328
0535226−051411
0535226−051508
0535226−051613

0535224−050805
0535224−050911
0535225−050800

0535222−051808
0535223−050739

0535219−050803
0535219−051704
0535219−051427

0535219−051501

0535218−050701

2MASS

ID
R.A.a
736
35:23.22
737
35:23.24
738
35:23.27
739
35:23.27740
35:23.30
741
35:23.30
742
35:23.30
743
35:23.33
744
35:23.35745
35:23.40
746
35:23.41
747
35:23.42748
35:23.47
749
35:23.48
750
35:23.54751
35:23.59752
35:23.60
753
35:23.65754
35:23.77755
35:23.82756
35:23.89757
35:23.92758
35:23.92759
35:23.96760
35:23.99761
35:24.00
762
35:24.06763
35:24.06764
35:24.09765
35:24.14766
35:24.14
767
35:24.34
768
35:24.38
769
35:24.49
770
35:24.55
771
35:24.61
772
35:24.63
773
35:24.63774
35:24.64(cont.)

decl.a−5:08:43.6−5:00:38.2−5:13:48.3−5:15:43.4−4:56:11.9−4:57:20.7−5:03:23.4−5:07:09.6−5:08:21.6−5:12:03.1−5:18:50.6−5:01:28.7−5:10:51.7−5:15:23.4−5:18:57.0−5:19:11.9−5:19:30.2−5:01:40.3−5:18:39.8−4:59:24.9−5:18:20.9−5:04:11.6−5:06:01.7−5:07:53.4−5:19:07.4−5:18:38.6−4:56:30.4−5:19:23.3−5:09:06.7−5:18:54.3−5:19:27.6−5:01:20.5−5:14:57.9−5:16:59.8−5:00:21.1−5:11:58.3−5:11:29.5−5:19:33.2−5:06:25.9

J bcd>21.11
16.56
15.35
15.68
16.82
12.90
17.01
17.79
16.80
15.96
11.32
>21.42
11.17
14.05
11.89
14.82
14.97
>21.02
12.53
18.49
17.02
16.88
>20.88
18.29
12.92
12.59
15.69
14.72
14.50
17.72
15.23
>21.10
16.57
11.65
18.00
11.29
12.20
16.14
16.95

H bcd
14.94
13.90
14.29
14.41
14.30
12.05
14.35
14.78
14.26
15.03
10.54†>20.47
11.06
13.38
11.14
13.71
13.83
18.18
11.62
16.70
13.95
15.33
17.96
16.64
12.14
11.86
15.06
13.35
13.90
15.13
13.55
19.52
14.66
10.75†
15.88
10.96†
11.30
13.21
15.16

K cd
13.10
12.44
13.53
13.39
12.95
11.92
12.85
12.51
12.41
12.47
10.23†
16.17
10.40†
12.93
11.18†
12.60
12.28
14.94
10.90†
15.75
12.20
14.48
14.38
15.26
11.80
11.20
14.82
11.96
13.51
13.41
12.01
14.68
13.58
10.18†
14.07
10.41†
10.18†
11.47
13.89
0535246−051158
0535246−051129

0535243−051457
0535244−051659

0535240−050906

0535239−051907

0535237−051839

0535235−051857

0535234−051051

0535234−051850

2MASS

257

ID
R.A.a
775
35:24.66
776 35:24.69
777 35:24.72
778
35:24.74
779
35:24.79
780 35:24.88
781 35:24.94
782 35:25.03
783 35:25.03
784
35:25.15
785 35:25.24
786 35:25.25
787 35:25.34
788 35:25.38
789 35:25.42
790 35:25.44
791
35:25.56
792 35:25.64
793 35:25.66
794
35:25.66
795 35:25.67
796 35:25.68
797 35:25.70
798 35:25.73
799 35:25.75
800 35:25.76
801
35:25.87
802
35:26.02
803 35:26.06
804 35:26.16
805 35:26.29
806 35:26.31
807
35:26.34
808 35:26.36
809 35:26.38
810
35:26.41
811 35:26.41
812
35:26.44
813 35:26.45(cont.)

decl.a−5:19:09.5−5:09:26.4−5:16:41.1−5:06:56.2−5:10:29.5−5:06:21.5−5:12:55.9−5:09:09.4−5:19:25.2−5:06:30.7−5:15:35.7−5:09:27.5−5:12:05.7−5:16:36.1−5:10:48.0−4:54:04.1−4:55:27.0−5:07:57.1−5:09:41.9−5:18:04.2−4:57:18.3−5:00:28.4−5:07:03.0−5:07:46.2−5:09:49.3−5:05:57.9−5:07:56.4−5:19:12.9−5:08:37.7−5:08:33.4−5:08:39.9−5:15:11.4−5:17:44.7−5:10:50.4−5:18:57.6−5:16:12.5−5:16:37.9−5:00:56.9−5:15:05.4

J bcd
11.86
17.01
13.85
>21.27<10.34
16.08
16.92
14.60
15.21
>21.86
11.72
11.82
14.09
16.39
11.62
13.72
14.90
11.82†
18.17
13.96
13.33
18.50
13.74
14.74
11.39
16.37
11.14
>22.41
12.61†
14.55
10.10†
10.25†
15.16
14.76
16.24
13.31
14.79
14.85
16.74

H bcd
10.99†
15.11
11.68>20.32
<8.79
12.93
16.23
13.96
13.95
18.45
10.81†
11.25
13.19
16.17
11.30
13.01
12.98
11.15†
15.94
12.94
12.59
16.77
13.14
12.36
10.48†
14.53
11.00†>21.4612.02†
13.78
9.60†
9.85†
14.58
14.04
14.02
11.91
13.87
14.12
15.63

K cd
10.29†
13.55<10.38
14.23
<7.16
11.07
13.87
13.49
12.76
16.58
10.09†
11.03
12.93
15.55
11.15
12.89
12.33
10.22†
13.91
12.31
12.40
15.98
12.95
11.22
10.11†
12.66
10.09†
18.22
10.03†
13.39
9.35†
9.80†
13.75
13.74
12.77
11.15
13.00
13.88
15.14
0535264−050057

0535264−051612

0535263−051050

0535262−050840
0535263−051511

0535260−050837

0535258−050756

0535257−050703
0535257−050746
0535257−050949

0535256−045718

0535254−051048
0535254−045403
0535255−045526
0535256−050757

0535252−051535
0535252−050927
0535253−051205

0535250−050909

0535248−050621

2MASS
0535246−051909

ID
R.A.a
814
35:26.46815
35:26.49
816
35:26.51817
35:26.58
818
35:26.58
819
35:26.58820
35:26.59821
35:26.62822
35:26.63823
35:26.64824
35:26.73825
35:26.75
826
35:26.75
827
35:26.87
828
35:26.87829
35:26.94830
35:26.94831
35:26.96832
35:26.96833
35:26.97834
35:27.00
835
35:27.01836
35:27.06837
35:27.18
838
35:27.21839
35:27.27840
35:27.44841
35:27.44842
35:27.45843
35:27.47844
35:27.49
845
35:27.49
846
35:27.53847
35:27.53848
35:27.55
849
35:27.56
850
35:27.59851
35:27.64852
35:27.64(cont.)

decl.a−4:59:51.9−5:17:56.6−5:19:18.7−4:58:25.3−5:17:53.1−5:19:08.3−4:56:06.7−5:03:54.6−5:18:18.6−4:55:02.5−5:16:45.2−5:14:44.5−5:19:02.8−5:09:24.6−5:17:13.1−5:04:07.0−5:18:06.9−5:11:07.7−5:15:37.2−5:10:17.4−5:13:14.5−5:09:54.4−5:15:44.8−4:58:34.5−4:55:18.6−5:05:27.2−5:02:42.4−5:09:04.0−5:17:12.1−5:17:09.8−5:09:44.3−5:11:50.1−5:13:56.4−5:16:55.9−5:18:19.3−5:10:08.6−5:05:31.2−4:54:38.9−5:09:32.9

J bcd
16.69
12.20
>21.18
20.52
12.11
18.17
11.85
14.89
16.06
16.78
13.11
15.07
16.15
15.18
16.50
15.90
13.84
8.92†
>21.73
13.23
10.55†
14.83
12.83
18.91
14.05
17.52
16.87
15.09
11.21
11.20
11.66
16.27
13.71
14.09
14.72
16.73
19.96
19.09
13.65

H bcd
14.21
<10.86>20.23
16.46
12.38†>19.94
11.32
12.12
16.08
15.56
12.28
14.39
14.06
13.21
15.52
14.22
12.63
7.84†
17.64
10.93†
10.26†
13.41
11.91
16.61
12.74
16.54
13.34
14.35
<10.36
10.24†
10.51†
15.16
12.46
12.79
13.06
14.27
19.55
17.33
<10.76K cd
12.89<10.21
12.61
14.51
11.36†
13.97
10.93†
<9.96
14.53
15.03
11.87
14.19
12.70
11.17
14.37
13.11
11.88
7.03†
16.10
8.73†
10.17†
12.55
11.25
15.59
12.29
15.61
11.04
13.80
<9.78
9.53†
9.83†
13.45
11.60
12.26
12.17
12.36
14.99
16.73
<9.14
0535275−051356

0535274−051709
0535274−050944

0535274−050903

0535272−045518

0535269−051017
0535269−051314
0535269−050954
0535270−051544

0535268−051107

0535268−050924

0535266−045502
0535267−051645
0535267−051444

0535265−045606

0535265−051753

2MASS

258
APPENDIX B. QUIRC SOURCES AND 2MASS COUNTERPART

ID
R.A.a
853
35:27.65854
35:27.66855
35:27.67856
35:27.75
857
35:27.81858
35:27.86
859 35:27.93860
35:27.94
861 35:27.97
862
35:28.01863
35:28.05864
35:28.05
865 35:28.06
866
35:28.14
867 35:28.15
868
35:28.17
869 35:28.17
870 35:28.19
871
35:28.19
872 35:28.19
873
35:28.26
874 35:28.30
875 35:28.36
876 35:28.36
877
35:28.40
878 35:28.41
879
35:28.43
880 35:28.44881
35:28.46882
35:28.52883
35:28.60
884 35:28.60
885 35:28.66
886 35:28.71
887 35:28.87
888 35:28.88889
35:28.93
890 35:28.94
891 35:29.04(cont.)

decl.a−5:18:00.7−5:09:37.3−5:09:49.9−5:18:04.7−5:07:54.8−5:05:36.3−5:16:57.3−4:53:52.1−5:18:59.8−5:19:14.0−5:05:38.4−5:17:20.3−5:01:35.1−5:18:57.0−5:10:13.9−5:00:49.8−5:15:50.9−5:03:41.3−5:11:37.6−5:16:01.4−4:58:38.4−4:55:42.1−5:17:54.4−5:18:23.0−4:58:07.2−5:07:44.1−5:19:02.0−4:53:57.0−4:57:16.9−5:07:46.9−4:55:03.8−5:05:44.6−5:02:44.8−5:19:25.7−4:57:39.3−4:54:36.1−4:54:20.6−5:16:18.4−5:06:04.0

J bcd
13.15
13.25
12.74
11.98
14.20
>20.99
11.60
17.69
13.90
>21.03>21.13
12.45
19.33
13.36
11.03
12.53
14.06
20.45
12.96
14.70
>21.06
17.33
13.52
12.34
14.65
16.22
13.23
17.46
>21.66
16.23
11.05
15.04
15.49
18.58
18.00
18.68
14.93
11.22
11.93

H bcd
12.08
10.51†
11.74
10.55†
13.28
16.26
10.86†
16.71
11.53
15.78
17.06
11.69
14.97
11.03
10.19†
11.74
12.54
16.61
11.87
14.16
14.14
15.79
12.36
11.64
13.88
13.07
12.59
16.42
18.34
13.05
10.54†
12.50
13.83
15.86
14.98
16.39
13.91
10.37†
11.41

K cd
11.64
8.94†
<10.60
9.94†
12.75
13.37
10.56†
17.04<10.25
14.36
14.49
11.43
12.18
9.68†
9.48†
11.51
11.78
11.84
11.55
13.15
11.39
14.98
11.93
11.46
13.67
11.11
12.22
15.95
16.67
11.09
10.38†
10.81†
12.99
15.62
13.11
15.28
13.34
9.63†
11.12
0535289−045420
0535289−051618
0535290−050604

0535286−045503
0535285−050544
0535286−050244

0535284−051902

0535283−051754
0535283−051823
0535283−045807

0535281−051137

0535281−051857
0535281−051013
0535281−050049

0535280−051720

0535279−051657

0535277−051804
0535277−050754

0535276−050937

2MASS

ID
R.A.a
892
35:29.14893
35:29.17894
35:29.37
895
35:29.37
896
35:29.44897
35:29.45898
35:29.45899
35:29.46
900
35:29.51901
35:29.54902
35:29.55
903
35:29.56904
35:29.79905
35:29.82906
35:29.90907
35:29.91908
35:29.93909
35:29.93910
35:30.00
911
35:30.07912
35:30.11913
35:30.15
914
35:30.22915
35:30.23916
35:30.26
917
35:30.28
918
35:30.29
919
35:30.36920
35:30.46921
35:30.48
922
35:30.53923
35:30.54924
35:30.59925
35:30.61
926
35:30.63927
35:30.65928
35:30.70929
35:30.72930
35:30.73(cont.)

decl.a−5:00:18.2−5:18:18.3−5:02:14.8−5:11:46.9−4:55:45.6−5:16:33.4−5:17:55.4−5:18:45.6−5:00:00.5−5:17:47.1−5:18:40.0−4:59:56.7−4:56:11.7−5:16:06.3−5:18:53.0−5:12:10.3−4:57:08.2−5:08:20.2−5:12:27.4−5:19:06.4−5:09:09.5−5:14:18.5−5:16:57.5−5:08:19.1−5:09:32.3−4:55:53.9−5:13:52.6−5:18:05.6−5:19:00.7−5:19:33.9−5:17:15.2−5:03:34.5−4:57:21.5−4:59:36.0−5:15:16.2−5:04:11.1−5:18:07.0−5:03:35.5−4:55:49.8

J bcd
19.47
14.67
17.10
>22.20
19.09
11.52
14.22
13.94
>21.44>22.05
14.99
18.00>21.50
11.98
16.14
12.64
14.25
>20.63
12.06
17.64
13.75
13.03
16.83
>20.74
17.07
18.00
13.29
14.26
15.10
13.94
14.01
15.42
14.77
14.36
13.65
18.32
12.38
15.35
18.66

H bcd
16.58
13.71
15.44
>21.2517.69
10.73†
13.20
12.26
20.19
17.75
13.46
17.21
>20.55
11.26
13.70
12.08
12.35
15.57
11.43
16.37
13.24
12.00
15.90
15.79
16.03
16.27
11.66
13.36
13.39
12.03
12.68
13.67
14.01
11.65
13.11
16.47
11.40
13.61
16.92

K cd
15.32
13.09
14.63
17.51
16.73
10.44†
12.26
10.09†
16.25
18.06
12.71
16.07
16.53
10.94†
12.19
11.85
11.60
13.12
10.86†
15.14
13.20
11.35
15.04
13.52
14.21
15.42
10.70†
13.09
12.33<10.40
12.15
12.75
13.74
10.48†
12.88
15.02
10.98†
12.75
16.51
0535307−051807
0535307−050335

0535305−050334
0535305−045721
0535306−045936
0535306−051516

0535302−051352

0535301−050909
0535301−051418

0535299−051227

0535299−051210
0535299−045708

0535298−051606

0535294−051845

0535294−051633

2MASS

259

ID
R.A.a
931
35:30.80932
35:30.80
933 35:30.89
934 35:30.91
935 35:30.97
936
35:31.03
937 35:31.04
938 35:31.04
939 35:31.07
940 35:31.13
941
35:31.14942
35:31.14
943 35:31.20
944 35:31.21
945 35:31.22
946 35:31.26
947 35:31.27
948
35:31.29
949 35:31.33
950 35:31.44
951 35:31.48
952 35:31.51
953
35:31.54
954 35:31.54
955
35:31.55
956 35:31.58
957 35:31.59
958 35:31.59
959
35:31.61960
35:31.62
961 35:31.64
962 35:31.64
963 35:31.75
964 35:31.76
965 35:31.97
966 35:31.98
967 35:32.00
968 35:32.01
969
35:32.02(cont.)

decl.a−4:54:43.7−4:58:13.6−4:55:17.9−5:18:17.8−5:04:44.1−4:57:20.0−5:18:07.6−5:18:44.9−5:04:15.0−5:15:13.9−4:54:15.2−5:13:43.8−4:57:27.1−5:12:27.9−5:19:31.8−5:15:10.7−5:18:55.7−5:15:32.9−5:12:01.5−5:16:03.4−4:57:47.7−5:05:01.6−5:05:47.2−5:14:44.7−5:16:36.8−5:15:23.4−4:54:37.4−5:06:25.0−5:19:27.5−5:16:58.1−5:00:14.0−5:03:46.1−5:16:39.8−5:14:52.2−5:09:27.9−5:15:59.5−5:16:20.0−4:55:35.7−5:08:05.8

J bcd
16.89
17.83
11.87
11.54
18.65
12.27
16.56
13.26
11.51
15.79
9.15†
16.40
14.92
12.94
14.28
15.14
10.80†
10.07†
14.53
5.84†
16.88
12.16
11.83
>21.33
12.59
13.00
14.88
17.22
>21.29
12.98
14.11
18.52
12.80
11.38
9.37†
11.64
12.56
13.94
14.14

H bcd
15.23
14.50
11.36
10.80†
16.77
11.50
15.84
12.37
11.01
15.33
9.20†
14.14
13.00
12.33
13.21
14.12
10.07†
9.28†
13.95
5.64†
15.07
11.57
9.77†
15.97
11.58
12.07
13.40
16.52
14.48
11.72
11.53
16.24
11.86
10.03†
8.54†
11.03
12.58
13.24
12.90

K cd
14.54
12.78
10.68†
10.46†
15.46
11.28
16.24
11.87
10.41†
15.62
9.22†
13.03
12.03
12.16
12.63
13.83
9.58†
8.93†
13.61
5.56†
14.14
10.77†
8.28†
15.55
10.85†
11.74
12.74
14.95
13.09
11.25
9.96†
15.38
11.32
9.47†
8.09†
<10.68
11.56
13.02
12.76
0535319−051620
0535320−045535
0535320−050805

0535317−051639
0535317−051452
0535319−050927

0535316−051658
0535316−050014

0535315−051636
0535315−051523
0535316−045437

0535312−051855
0535312−051533
0535313−051201
0535313−051602
0535314−045747
0535315−050501
0535315−050547

0535311−045415
0535311−051343
0535312−045727
0535312−051228

0535310−051845
0535310−050415

0535310−045720

0535308−045517
0535309−051817

2MASS

ID
R.A.a
970
35:32.03971
35:32.04972
35:32.10973
35:32.19974
35:32.20
975
35:32.31
976
35:32.34
977
35:32.34
97835:32.36979
35:32.38980
35:32.39981
35:32.43982
35:32.44983
35:32.53984
35:32.54985
35:32.62986
35:32.64987
35:32.64
988
35:32.72
989
35:32.81990
35:32.84991
35:32.90992
35:32.92993
35:32.93994
35:32.95995
35:32.96996
35:32.96997
35:33.02998
35:33.10
999
35:33.12
1000
35:33.171001
35:33.211002
35:33.34
1003
35:33.43
1004
35:33.441005
35:33.45
1006
35:33.49
1007
35:33.58
1008
35:33.59(cont.)

decl.a−5:08:34.9−4:56:42.4−5:00:23.7−5:11:57.8−5:16:03.6−5:16:26.8−5:11:43.3−5:18:07.7−4:58:29.9−5:12:53.0−5:12:10.8−5:14:24.6−5:15:06.7−5:01:57.2−5:02:09.8−5:05:37.9−4:56:52.7−5:15:51.2−5:12:00.7−5:17:38.5−5:18:19.8−5:16:30.2−5:16:05.3−5:02:46.8−4:57:54.2−5:12:04.8−5:16:40.1−5:17:39.2−5:13:38.7−5:17:34.0−5:14:10.6−5:16:05.4−5:11:45.6−4:56:54.5−5:08:45.1−4:56:01.7−5:05:00.9−4:55:17.9−5:15:23.2

J bcd
17.13
16.08
15.57
12.63
12.52
14.00
14.92
11.53
17.18
16.61
19.48
12.68
13.61
15.39
14.86
15.74
18.45
13.49
15.52
13.36
13.90
15.67
11.31
17.58
18.03
13.27
14.52
14.51
>20.85
12.84
12.20
11.45
17.54
17.67
>21.31
13.03
19.23
18.29
13.13

H bcd
15.86
14.79
13.91
11.92
12.04
12.92
12.67
10.67†
14.54
16.22
18.40
11.66
12.25
13.60
14.12
14.84
17.21
12.42
14.12
12.28
12.44
17.92
10.50†
15.60
16.25
11.52
13.98
13.26
>19.9012.17
11.47
10.74†
16.58
16.44
20.12
12.33
15.91
17.84
11.84

K cd
15.32
14.24
13.06
11.54
11.70
12.51
11.57
10.30†
13.10
16.39
17.13
11.43
11.45
12.65
13.76
14.32
16.33
11.99
12.80
11.78
11.62
13.98
10.16†
14.51
15.59
10.55†
13.07
12.54
13.92
11.85
11.06
9.82†
15.32
16.02
15.20
12.09
14.19
16.25
11.42
0535335−051523

0535334−045601

0535331−051733
0535331−051410
0535331−051605

0535329−051204

0535329−051605

0535328−051738

0535326−051551

0535324−051424
0535324−051506
0535325−050157
0535325−050209
0535326−050538

0535323−051143
0535323−051807

0535320−045642
0535321−050023
0535321−051157

2MASS

260
APPENDIX B. QUIRC SOURCES AND 2MASS COUNTERPART

ID
R.A.a
1009 35:33.63
1010 35:33.65
1011 35:33.68
1012 35:33.80
1013 35:33.83
1014 35:33.84
1015 35:33.88
1016 35:33.88
1017 35:33.92
1018 35:34.00
1019 35:34.03
1020 35:34.08
1021 35:34.29
1022 35:34.42
1023 35:34.46
1024 35:34.50
1025 35:34.52
1026 35:34.58
1027 35:34.59
1028 35:34.62
1029 35:34.80
1030 35:34.98
1031 35:35.04
1032 35:35.20
1033 35:35.28
1034 35:35.34
1035 35:35.35
1036 35:35.40
1037 35:35.45
1038 35:35.55
1039 35:35.60
1040 35:35.68
1041 35:35.77
1042 35:35.79
1043 35:35.93
1044 35:35.97
1045 35:35.98
1046 35:36.01
1047 35:36.02(cont.)

decl.a−5:00:42.0−5:03:08.0−4:57:20.9−4:55:00.2−5:04:27.5−5:17:10.8−5:09:06.2−5:15:54.4−5:03:33.5−4:53:57.6−4:54:11.0−5:17:09.5−5:06:21.2−5:18:38.4−5:03:30.7−5:00:52.4−5:13:07.7−5:19:05.5−4:57:52.8−5:15:52.8−5:15:31.2−5:12:30.2−5:11:09.2−5:00:14.7−4:58:02.2−5:05:24.9−5:11:11.5−5:08:46.9−5:07:53.1−5:06:58.6−5:15:43.2−5:10:51.0−4:56:27.6−5:12:20.5−5:12:06.8−5:11:01.0−5:02:12.6−5:12:25.2−4:57:41.6

J bcd
12.01
13.29
18.10
13.11
13.82
14.40
13.96
14.27
12.54
13.48
12.73
15.36
9.31†
15.23
17.73
16.28
14.32
15.89
18.56
12.98
14.13
14.50
14.16
18.10
18.40
17.22
12.61
13.84
16.31
13.28
11.66
14.13
16.93
9.79†
18.41
19.93
18.14
11.20†
14.47

H bcd
11.30
11.77
16.72
12.09
11.82
13.27
13.40
12.96
11.97
12.08
12.04
14.47
9.33†
13.66
16.63
13.69
13.74
14.33
16.93
12.33
12.94
13.83
13.40
15.92
16.61
15.08
12.05
13.09
14.28
12.68
10.96†
13.64
15.51
9.84†
17.06
17.39
16.66
9.57†
13.73

K cd
11.03
10.89†
16.10
11.69
10.53†
12.82
13.22
12.32
11.74
11.61
11.88
14.26
9.31†
12.42
16.21
11.28
13.58
13.08
15.64
11.71
12.29
12.85
12.91
15.55
15.68
13.89
11.88
12.87
13.07
12.53
10.64†
13.36
15.05
9.76†
16.92
16.26
16.04
8.47†
13.47
0535360−051225
0535360−045741

0535357−051220

0535353−051111
0535353−050846
0535354−050753
0535355−050658
0535356−051543
0535356−051050

0535350−051109

0535346−051552
0535348−051531

0535345−050052
0535345−051307

0535342−050621

0535338−045500
0535338−050427
0535338−051710
0535338−050905
0535338−051554
0535339−050333
0535340−045357
0535340−045411

2MASS
0535336−050042
0535336−050308

ID
R.A.a
1048
35:36.05
1049
35:36.211050
35:36.26
1051
35:36.421052
35:36.441053
35:36.48
1054
35:36.57
1055
35:36.57
1056
35:36.58
1057
35:36.67
1058
35:36.68
1059
35:36.691060
35:36.72
1061
35:36.74
1062
35:36.871063
35:36.891064
35:36.95
1065
35:36.951066
35:36.971067
35:37.06
1068
35:37.16
1069
35:37.18
1070
35:37.33
1071
35:37.45
1072
35:37.59
1073
35:37.70
1074
35:37.891075
35:38.011076
35:38.011077
35:38.03
1078
35:38.10
1079
35:38.131080
35:38.19
1081
35:38.19
1082
35:38.221083
35:38.32
1084
35:38.45
1085
35:38.51
1086
35:38.53(cont.)

decl.a−5:13:17.1−5:04:55.8−5:14:30.2−5:01:15.5−5:09:11.5−5:15:32.3−5:04:39.2−5:12:31.0−4:58:40.6−5:18:50.7−5:04:14.4−4:57:29.9−4:56:44.7−5:10:00.4−4:58:05.0−5:18:21.6−5:03:26.2−5:04:05.3−5:05:26.2−5:18:58.6−5:10:29.5−4:56:53.7−5:02:36.3−4:58:26.8−5:04:47.1−5:06:31.9−5:03:46.2−4:57:13.5−5:03:29.8−5:19:26.7−5:18:11.1−4:55:41.0−4:56:37.0−5:03:33.7−5:14:18.8−4:58:01.2−5:10:08.9−5:04:51.4−4:59:41.0

J bcd
15.97
13.26
15.10
10.93†
16.63>21.51
12.05
15.77
17.64
14.14
11.98
13.61
18.74
13.13
13.73
>21.55
21.10
17.02
14.58
20.98
12.47
>21.64
15.27
11.69
17.66
12.96
17.42
18.79
17.46
17.55
11.53
14.26
>21.54
15.76
11.58
16.18
14.82
16.33
12.05

H bcd
14.77
11.76
14.49
10.07†
15.89
16.71
11.30
15.32
16.53
13.27
11.31
12.38
16.79
12.43
12.21
18.84
>20.73
15.84
14.06
18.74
11.81
>20.6913.16
10.01†
14.88
12.25
15.77
16.98
16.05
16.59
9.78†
13.11
>20.59
14.92
11.01
14.81
14.36
13.69
11.10

K cd
13.81
11.12
13.77
9.56†
15.41
15.55
11.15
14.56
16.11
12.80
10.87†
11.92
15.43
11.97
11.64
14.64
16.43
15.19
13.70
16.60
11.64
17.39
12.10
9.19†
13.22
12.10
15.20
16.46
15.64
15.96
8.86†
12.65
16.73
14.51
10.56†
14.31
14.13
11.95
<10.440535384−051009
0535385−050451

0535382−050333
0535382−051418

0535381−051811

0535376−050631
0535378−050346

0535373−050236
0535374−045826

0535371−051029

0535369−050526

0535367−051000
0535368−045805

0535366−051850
0535366−050414
0535366−045730

0535365−050439

0535364−050115

0535362−050455

2MASS

261

ID
R.A.a
1087 35:38.57
1088 35:38.58
1089 35:38.65
1090 35:38.72
1091 35:38.75
1092 35:38.79
1093 35:38.82
1094 35:38.83
1095 35:38.86
1096 35:38.98
1097 35:39.03
1098 35:39.08
1099 35:39.16
1100 35:39.20
1101 35:39.27
1102 35:39.29
1103 35:39.68
1104 35:39.73
1105 35:39.84
1106 35:39.92
1107 35:39.93
1108 35:39.97
1109 35:40.01
1110 35:40.03
1111 35:40.04
1112 35:40.17
1113 35:40.17
1114 35:40.19
1115 35:40.20
1116 35:40.25
1117 35:40.29
1118 35:40.32
1119 35:40.34
1120 35:40.38
1121 35:40.53
1122 35:40.56
1123 35:40.62
1124 35:40.63
1125 35:40.63(cont.)

decl.a−5:08:03.2−5:07:31.1−5:09:56.6−5:16:58.9−5:04:55.4−5:11:19.9−4:57:10.2−5:12:15.3−5:12:41.8−5:19:14.6−5:07:04.2−5:08:56.3−5:12:20.2−5:16:35.5−5:13:50.9−5:18:31.7−5:12:08.2−5:01:54.0−5:15:49.4−4:57:31.3−4:58:39.1−5:06:36.7−5:02:36.9−4:57:28.9−5:11:38.2−5:09:56.0−5:16:25.8−5:16:32.0−5:17:29.1−5:15:47.5−5:13:36.8−5:03:05.5−5:12:31.9−4:55:44.0−4:59:12.8−5:03:04.6−5:12:19.3−5:13:20.6−5:19:02.6

J bcd
15.91
17.86
12.98
13.44
14.95
17.78
16.12
15.40
10.87†>21.93
12.52
10.87†
13.72
14.12
18.14
>21.45>21.07>21.0914.01<10.95
12.82
12.48
14.12
11.06
16.71
18.34
>20.8815.58
10.35†>20.89
15.97
16.79
15.97
13.28
15.76
16.41
12.95
16.92
>21.13

H bcd
13.46
16.89
12.47
12.21
12.91
16.48
14.98
14.86
9.72†
17.56
11.97
10.20†
12.74
12.31
17.41
>20.50>20.12
15.62
12.89<10.32
11.99
11.47
13.45
<10.38
14.97
15.51
14.62
13.67
9.53†
14.35
14.15
15.31
14.79
12.39
15.08
14.99
12.21
16.11
16.06

K cd
12.01
16.76
12.22
11.53
11.94
15.82
14.62
14.84
9.02†
16.32
11.79
10.00†
12.27
11.36
15.06
16.55
15.03
14.18
12.42
<9.93
11.82
10.91†
13.16
<9.97
14.49
14.88
14.13
13.17
9.01†
14.04
13.65
14.78
14.37
12.03
14.84
14.52
11.99
16.06
14.31
0535405−050304
0535406−051219

0535403−051232

0535402−051631
0535401−051729

0535399−050636
0535400−050236

0535398−051549

0535390−050704
0535390−050856
0535391−051220
0535392−051635

0535388−051215
0535388−051241

0535386−050956
0535387−051659
0535387−050455

2MASS
0535385−050803

ID
R.A.a
1126
35:40.65
1127
35:40.68
1128
35:40.681129
35:40.771130
35:40.781131
35:40.781132
35:40.80
1133
35:40.861134
35:40.961135
35:41.051136
35:41.10
1137
35:41.29
1138
35:41.35
1139
35:41.38
1140
35:41.38
1141
35:41.42
1142
35:41.57
1143
35:41.63
1144
35:41.74
1145
35:41.74
1146
35:41.77
1147
35:41.85
1148
35:41.991149
35:42.011150
35:42.041151
35:42.071152
35:42.16
1153
35:42.28
1154
35:42.29
1155
35:42.351156
35:42.50
1157
35:42.52
1158
35:42.61
1159
35:42.691160
35:42.69
1161
35:42.771162
35:42.971163
35:42.971164
35:43.06(cont.)

decl.a−5:19:33.0−5:01:53.3−5:03:56.1−5:12:47.9−5:09:01.6−5:11:11.9−5:18:39.1−5:18:32.6−5:16:57.5−5:06:25.3−5:09:55.8−5:03:52.2−5:16:41.3−5:04:38.8−5:12:58.9−5:16:44.9−5:16:05.5−4:56:53.9−5:03:29.0−5:05:19.8−4:58:13.9−5:01:25.6−5:17:36.4−5:10:11.5−5:16:11.2−5:12:59.4−5:19:09.3−5:15:59.3−5:15:08.0−5:11:57.4−5:12:38.2−4:59:40.1−5:01:03.4−5:10:16.3−5:10:49.1−5:11:54.7−4:57:43.5−5:19:05.8−5:03:07.3

J bcd
15.35
19.32
14.79
13.29
10.36†
13.67
16.80
16.50
15.97
12.55
17.10
14.17
16.81
17.04
11.31
16.88
15.10
12.64
13.41
15.37
17.95
15.61
18.17
11.46
17.89
13.37
17.89
16.86
13.55
15.19
15.35
12.58
15.77
14.64
19.76
11.20
13.62
18.82
13.32

H bcd
15.56
17.28
13.36
12.17
9.43†
13.09
15.84
15.81
15.31
11.89
16.59
12.92
16.07
15.70
10.61†
16.09
14.21
11.87
12.66
13.77
16.52
14.45
17.01
10.16†
16.91
12.81
16.96
15.44
12.08
14.73
14.70
11.83
14.38
14.13
17.17
10.47†
12.85
16.97
12.62

K cd
14.81
16.29
12.71
11.64
9.09†
12.74
14.95
15.29
15.12
11.67
16.00
12.43
15.21
14.93
10.38†
15.40
14.06
11.85
12.55
12.82
15.92
14.08
16.63
9.50†
16.75
12.51
15.86
14.91
11.60
14.54
13.89
11.79
13.89
13.73
16.24
10.28†
12.44
16.16
12.39
0535430−050307

0535427−051154
0535429−045743

0535425−045940
0535426−050103
0535426−051016

0535422−051507

0535420−051259

0535420−051011

0535418−050125

0535415−051605
0535416−045653
0535417−050329
0535417−050519

0535413−051258

0535413−050352

0535410−050625

0535406−050356
0535407−051247
0535407−050901
0535407−051111

2MASS

262
APPENDIX B. QUIRC SOURCES AND 2MASS COUNTERPART

ID
R.A.a
1165 35:43.11
1166 35:43.20
1167 35:43.25
1168 35:43.55
1169 35:43.55
1170 35:43.58
1171 35:43.63
1172 35:43.64
1173 35:43.65
1174 35:43.66
1175 35:43.66
1176 35:43.80
1177 35:43.81
1178 35:43.93
1179 35:43.96
1180 35:44.03
1181 35:44.09
1182 35:44.09
1183 35:44.35
1184 35:44.50
1185 35:44.53
1186 35:44.59
1187 35:44.61
1188 35:44.70
1189 35:44.71
1190 35:44.79
1191 35:44.86
1192 35:44.93
1193 35:44.95
1194 35:44.99
1195 35:45.07
1196 35:45.12
1197 35:45.19
1198 35:45.24
1199 35:45.32
1200 35:45.38
1201 35:45.48
1202 35:45.58
1203 35:45.61(cont.)

decl.a−5:13:46.8−4:58:23.3−5:09:17.0−5:05:41.3−5:08:49.4−5:09:33.9−5:01:52.8−4:56:54.0−5:17:28.7−5:07:07.5−5:17:25.5−5:14:39.1−5:09:58.7−5:14:04.8−5:03:42.9−4:56:18.5−5:08:37.5−5:12:56.5−4:57:16.8−5:07:31.6−5:08:56.3−4:56:24.8−4:59:57.6−5:00:39.6−4:58:35.3−4:58:12.4−5:07:16.8−4:57:01.4−5:15:20.1−4:56:02.8−5:13:55.4−5:17:27.3−5:00:47.6−5:07:09.1−5:19:08.3−5:10:11.9−5:09:45.9−5:18:02.9−5:18:13.3

J bcd
10.19†
13.76
10.78†
11.96
15.95
16.28
>21.29
20.18
15.20
17.82
14.27
14.37
13.61
18.45
14.86
15.56
14.63
17.36
13.23
12.07
16.12
16.81
14.92
14.00
16.18
18.62
10.09†
16.12
14.43
13.57
16.70
17.34
17.01
15.94
15.69
16.30
>21.90
13.07
12.55

H bcd
9.89†
13.03
10.08†
11.48
14.90
15.26
16.89
>20.76
14.08
16.87
13.20
13.47
13.07
17.19
13.63
14.54
13.19
16.33
12.49
11.60
14.93
15.58
14.26
13.13
15.01
16.83
9.45†
15.40
13.39
12.63
15.34
16.38
15.85
15.02
13.82
14.67
>20.95
13.80
11.52

K cd
9.78†
12.78
9.88†
10.38†
14.26
14.92
15.99
16.23
13.64
16.09
12.79
13.16
12.71
16.53
13.09
13.90
11.86
16.22
12.25
11.30
14.18
15.37
14.01
12.89
14.65
15.90
9.17†
14.80
13.10
12.39
15.36
16.36
15.53
14.43
12.92
13.90
16.95
13.04
11.37
0535456−051813

0535452−050709
0535453−051908
0535453−051012

0535448−050716
0535449−045701
0535449−051520
0535450−045602

0535443−045716
0535445−050731
0535445−050856
0535446−045625
0535446−045957
0535447−050039
0535447−045835

0535439−050343
0535440−045618
0535440−050837

0535436−051725
0535437−051439
0535438−050958

2MASS
0535431−051346
0535431−045823
0535432−050917
0535435−050541
0535435−050849
0535435−050933

ID
R.A.a
1204
35:45.621205
35:45.631206
35:45.70
1207
35:45.71
1208
35:45.971209
35:46.021210
35:46.071211
35:46.10
1212
35:46.11
1213
35:46.13
1214
35:46.141215
35:46.20
1216
35:46.24
1217
35:46.26
1218
35:46.31
1219
35:46.48
1220
35:46.49
1221
35:46.56
1222
35:46.57
1223
35:46.621224
35:46.67
1225
35:46.821226
35:46.901227
35:47.011228
35:47.021229
35:47.091230
35:47.171231
35:47.20
1232
35:47.25
1233
35:47.39
1234
35:47.421235
35:47.47
1236
35:47.48
1237
35:47.50
1238
35:47.54
1239
35:47.541240
35:47.791241
35:47.83
1242
35:47.83(cont.)

decl.a−5:18:42.6−5:13:36.0−5:14:05.4−5:10:55.3−5:16:09.9−4:55:31.9−5:17:49.4−5:12:24.3−4:56:41.0−5:10:51.8−5:00:43.4−4:58:49.5−5:15:39.8−5:16:25.4−5:13:24.3−4:58:17.8−4:57:54.8−5:03:41.3−5:05:33.4−5:15:55.5−5:17:29.0−5:16:46.8−5:10:43.3−5:16:14.1−5:06:13.2−5:14:42.5−5:00:44.9−5:16:43.2−5:17:43.1−5:13:18.5−5:10:28.5−5:00:46.9−5:14:30.4−5:16:57.8−5:07:10.0−5:12:18.1−5:10:30.8−4:58:54.6−5:13:17.7

J bcd
15.22
13.30
18.67
13.54
17.08
15.16
12.34
18.08
17.39
12.02
16.68
15.20
12.64
>21.37
16.52
15.33
16.59
16.37
18.25
20.34
16.52
12.77
14.12
15.22
16.22
15.26
16.16
16.27
12.15
11.58
11.17
17.69
17.51
10.42†
16.16
12.88
10.18†
17.95
13.29

H bcd
13.83
12.25
16.52
13.03
15.40
13.98
11.56
16.30
16.15
11.23
15.45
14.07
11.53
19.05
15.40
14.24
15.51
15.17
16.39
15.90
14.43
11.88
13.22
14.52
15.31
14.10
15.39
15.94
11.64
11.03†
10.88†
16.58
16.25
10.06†
14.95
12.23
9.64†
16.38
12.08

K cd
14.24
11.67
15.35
12.68
14.04
13.78
11.06
14.77
15.69
10.62†
15.16
13.70
10.98†
15.92
15.04
13.94
15.29
14.65
15.24
15.59
14.33
11.55
12.89
13.88
14.96
13.59
15.13
15.85
11.33
10.84†
10.47†
16.01
15.35
9.93†
14.57
12.21
9.40†
15.91
11.70
0535478−051317

0535475−051657
0535475−050709
0535475−051218
0535477−051030

0535473−051318
0535474−051028

0535471−050044

0535470−050612

0535468−051646
0535469−051043

0535464−045817
0535465−045755
0535465−050341

0535461−051051
0535461−050043
0535462−045849
0535462−051539

0535460−045532
0535460−051749

0535457−051055

2MASS
0535456−051842
0535456−051336

263

ID
R.A.a
1243 35:48.01
1244 35:48.11
1245 35:48.26
1246 35:48.32
1247 35:48.39
1248 35:48.39
1249 35:48.50
1250 35:48.55
1251 35:48.59
1252 35:48.62
1253 35:48.76
1254 35:48.84
1255 35:48.96
1256 35:48.99
1257 35:49.02
1258 35:49.03
1259 35:49.66
1260 35:49.66
1261 35:49.80
1262 35:49.81
1263 35:49.84
1264 35:50.03
1265 35:50.06
1266 35:50.08
1267 35:50.12
1268 35:50.12
1269 35:50.41
1270 35:50.56
1271 35:50.58
1272 35:50.66
1273 35:50.76
1274 35:50.77
1275 35:50.82
1276 35:50.84
1277 35:51.02
1278 35:51.05
1279 35:51.08
1280 35:51.31
1281 35:51.45(cont.)

decl.a−5:08:11.6−5:15:24.7−5:11:10.3−4:57:42.7−5:01:28.7−5:08:52.6−5:15:35.7−5:15:21.1−5:17:42.6−5:11:53.2−4:58:38.5−5:00:28.5−5:09:53.0−5:01:39.3−5:15:52.7−5:15:37.6−5:00:34.7−5:06:02.7−5:06:39.7−4:58:22.8−5:15:12.8−5:17:17.8−4:58:16.1−5:09:46.2−5:10:29.4−5:17:00.2−5:17:29.9−5:16:11.7−5:09:20.9−5:14:58.9−5:16:28.9−5:16:53.3−5:09:29.9−5:05:49.3−5:17:33.0−5:15:08.7−5:07:08.7−5:11:59.9−5:08:01.8

J bcd
15.09
17.39
12.79
15.50
12.24
17.59
17.07
15.18
14.56
16.72
18.01
12.66
16.15
12.61
15.95
13.13
17.47
13.26
15.48
18.37
15.44
14.98
14.46
13.39
13.22
17.76
17.44
17.67
14.29
17.39
11.36
16.69
8.49†
17.74
17.36
11.81
11.01
15.92
15.59

H bcd
13.61
16.42
11.95
14.25
11.39
16.40
16.18
14.39
13.49
15.78
16.70
11.67
15.11
11.81
15.15
12.33
16.16
12.57
14.69
17.06
14.65
14.01
13.26
12.48
12.64
16.51
16.38
16.13
13.18
16.58
10.65†
15.46
7.20†
16.41
16.41
11.30†
10.28†
14.98
14.30

K cd
12.78
15.92
11.66
13.83
10.21†
16.05
16.14
14.15
13.09
15.56
16.50
11.35
14.60
11.53
14.97
12.07
15.67
12.46
14.41
16.58
14.24
13.54
12.93
12.15
12.37
16.60
15.82
15.93
12.55
14.31
10.21†
15.15
6.67†
15.65
15.31
10.97†
9.87†
14.80
13.52
0535510−051508
0535510−050708

0535508−050930

0535507−051629

0535500−051718
0535500−045816
0535500−050946
0535501−051029

0535496−050602
0535497−050639

0535490−051537

0535488−050028
0535489−050953
0535489−050139

0535485−051521
0535485−051742

0535482−051110
0535483−045742
0535483−050128

2MASS
0535480−050811

ID
R.A.a
1282
35:51.49
1283
35:51.55
1284
35:51.56
1285
35:51.56
1286
35:51.64
1287
35:51.78
1288
35:51.82
1289
35:51.841290
35:51.931291
35:51.941292
35:51.961293
35:52.26
1294
35:52.29
1295
35:52.33
1296
35:52.48
1297
35:52.63
1298
35:52.77
1299
35:52.88
1300
35:52.891301
35:52.95
1302
35:53.091303
35:53.311304
35:53.351305
35:53.441306
35:53.541307
35:53.64
1308
35:53.71
1309
35:53.991310
35:54.00
1311
35:54.031312
35:54.091313
35:54.19
1314
35:54.20
1315
35:54.211316
35:54.32
1317
35:54.68
1318
35:54.69
1319
35:54.771320
35:54.80(cont.)

decl.a−5:17:22.6−4:57:11.7−5:09:01.9−5:15:09.5−5:08:09.0−5:17:39.2−4:58:45.2−5:15:30.5−5:14:16.5−5:11:56.6−5:03:57.7−5:13:18.6−4:57:41.8−5:12:57.0−4:57:04.2−5:05:05.3−5:12:59.0−4:59:29.0−4:58:34.4−5:01:18.3−5:10:17.9−4:57:26.2−5:01:16.0−5:09:39.2−5:02:34.7−5:10:09.6−5:02:00.7−5:10:40.0−5:00:30.7−5:04:14.9−5:13:29.8−5:14:43.8−5:05:45.4−5:13:43.0−5:11:52.3−5:05:21.3−5:06:27.8−5:10:55.6−4:59:20.2

J bcd
18.49
19.45
14.97
16.79
10.05†
13.44
18.65
14.80
14.72
17.41
16.41
13.91
19.09
12.84
16.64
9.84†
11.73
17.84
16.04
15.21
17.42
18.56
16.83
17.62
13.02
15.67
15.88
15.59
17.72
11.32†
16.79
17.22
13.43
>21.91
16.98
16.93
13.34
13.21
16.40

H bcd
17.31
17.98
14.14
16.19
9.42†
12.68
17.21
14.14
13.87
16.52
15.48
13.24
17.02
12.18
15.07
9.26†
11.07†
16.52
15.09
14.19
16.02
17.09
15.78
16.07
11.99
14.75
15.00
15.00
16.51
10.43†
16.30
15.95
12.79
18.38
16.07
15.79
12.85
12.61
15.17

K cd
16.57
16.07
13.83
16.02
9.24†
12.33
16.33
13.93
13.65
16.25
15.23
12.87
16.54
11.87
14.52
8.85†
10.45†
15.81
14.68
13.93
15.65
16.09
15.36
15.47
11.62
14.35
14.64
14.85
16.37
9.90†
16.01
15.93
12.61
17.27
15.82
15.08
12.57
12.47
14.75
0535546−050627
0535547−051055
0535548−045920

0535542−050545

0535540−050414

0535535−050234
0535536−051009
0535537−050200
0535539−051039

0535528−045834
0535529−050118

0535523−051256
0535524−045704
0535526−050505
0535527−051258

0535519−050357
0535522−051318

0535518−051530
0535519−051416

0535516−050809
0535517−051739

0535515−050901

2MASS

264
APPENDIX B. QUIRC SOURCES AND 2MASS COUNTERPART

ID
R.A.a
1321 35:54.82
1322 35:54.95
1323 35:54.97
1324 35:55.03
1325 35:55.06
1326 35:55.18
1327 35:55.35
1328 35:55.41
1329 35:55.45
1330 35:55.60
1331 35:55.65
1332 35:55.74
1333 35:55.94
1334 35:56.00
1335 35:56.02
1336 35:56.02
1337 35:56.04
1338 35:56.49
1339 35:56.55
1340 35:56.61
1341 35:56.69
1342 35:56.81
1343 35:56.84
1344 35:57.04
1345 35:57.14
1346 35:57.15
1347 35:57.24
1348 35:57.47
1349 35:57.47
1350 35:57.54
1351 35:57.61
1352 35:57.66
1353 35:57.89
1354 35:58.07
1355 35:58.10
1356 35:58.17
1357 35:58.19
1358 35:58.20
1359 35:58.22(cont.)

decl.a−5:00:48.9−5:10:27.9−5:13:15.5−5:03:16.1−5:02:37.3−5:14:42.6−5:14:13.9−5:09:50.2−5:13:55.3−5:10:00.4−5:08:11.9−5:04:37.7−5:00:07.5−5:05:37.3−5:00:51.5−5:12:09.0−5:09:03.1−5:10:30.7−4:58:58.7−5:02:16.5−4:59:02.5−5:13:28.9−4:59:14.6−5:01:40.7−5:01:49.5−5:02:31.9−5:07:22.4−5:05:32.2−5:08:29.1−5:08:44.2−5:10:02.6−5:10:29.6−5:12:18.0−5:12:54.3−5:11:42.7−5:13:07.1−5:11:22.9−5:11:53.8−5:09:32.1

J bcd
16.87
14.48
12.35
17.03
13.87
17.25
16.14
16.39
13.15
17.22
16.71
16.99
14.69
16.50
14.08
15.23
11.17
14.95
15.45
17.40
17.56
17.65
14.68
17.66
17.64
16.93
16.84
17.36
17.85
17.44
17.82
16.73
15.97
9.15†
15.49
17.04
17.81
16.51
15.16

H bcd
16.00
13.78
11.64
16.00
12.72
15.87
15.32
15.60
12.52
16.58
15.97
15.68
14.09
15.40
13.05
14.29
10.39†
14.35
14.44
16.29
16.43
16.58
14.11
16.52
16.79
15.94
16.11
16.29
16.80
16.60
16.83
16.19
15.33
8.30†
14.54
16.27
16.58
15.61
14.45

K cd
15.89
13.59
11.43
15.66
12.33
15.60
14.92
15.19
12.29
16.52
15.40
14.18
13.78
15.15
12.79
14.01
10.12†
14.22
14.09
15.75
16.07
16.44
13.77
15.94
16.23
15.72
15.70
16.05
16.48
16.34
16.22
15.97
15.05
8.05†
13.85
15.98
16.00
15.41
14.22
0535582−050932

0535580−051254

0535576−051029

0535568−045914

0535559−050007
0535560−050537
0535560−050051
0535560−051209
0535560−050903
0535564−051030
0535565−045858

0535554−050950
0535554−051355

0535550−050237

0535549−051027
0535549−051315

2MASS

ID
R.A.a
1360
35:58.27
1361
35:58.37
1362
35:58.74
1363
35:58.75
1364
35:58.81
1365
35:58.82
1366
35:59.00
1367
35:59.22
1368
35:59.22
1369
35:59.48
1370
35:59.61
1371
35:59.67
1372
35:59.71
1373
35:59.91
1374
35:59.931375
36:00.33
1376
36:00.45
1377
36:00.771378
36:00.921379
36:01.071380
36:01.271381
36:01.281382
36:01.31
1383
36:01.511384
36:01.55
1385
36:01.641386
36:01.74
1387
36:01.87
1388
36:02.171389
36:02.521390
36:02.631391
36:02.701392
36:02.731393
36:02.811394
36:02.87
1395
36:02.911396
36:02.931397
36:03.03
1398
36:03.04(cont.)

decl.a−5:00:48.1−5:06:27.4−4:59:32.2−4:59:19.8−5:10:14.6−5:00:26.1−5:12:40.6−4:58:46.2−5:07:33.7−5:10:21.4−5:01:28.7−5:01:38.6−5:06:43.5−5:00:37.7−5:04:31.0−5:05:00.0−5:05:54.0−4:59:14.7−5:08:48.7−5:03:09.3−5:01:59.2−5:07:56.4−5:07:39.1−5:00:21.0−5:11:55.3−5:10:40.4−4:59:24.3−5:08:35.1−5:00:13.1−5:04:42.1−5:07:36.5−5:04:18.9−5:04:44.7−5:04:23.7−5:09:00.1−5:05:43.3−5:07:53.2−5:01:11.0−5:07:18.7

J bcd
17.23
16.95
16.07
17.66
15.23
15.03
16.12
12.55
14.81
16.22
13.52
16.59
15.10
17.34
13.41
12.23
13.38
15.46
15.88
17.11
16.18
15.44
17.35
16.58
16.95
15.41
16.37
16.09
17.98
16.79
11.31
17.08
17.67
14.89
17.25
17.61
17.16
17.58
15.16

H bcd
16.09
16.19
14.85
16.18
14.66
14.38
15.38
11.83
14.24
15.19
12.62
15.31
14.28
15.98
12.82
11.66
12.83
14.53
15.17
15.99
15.23
14.71
16.34
15.18
16.08
14.83
15.21
15.18
16.97
16.05
10.69†
16.35
16.57
14.39
16.43
16.30
16.13
16.40
14.36

K cd
15.93
15.75
14.47
15.81
14.12
14.07
14.96
11.61
13.82
15.27
12.34
15.03
14.26
15.49
12.52
11.44
12.61
14.24
15.04
15.79
14.93
14.54
15.62
14.86
15.86
14.69
14.67
14.88
16.42
15.89
10.49†
16.23
16.25
14.06
16.27
15.65
15.45
15.97
14.16
0536030−050718

0536028−050423

0536026−050736

0536016−051040
0536017−045924
0536018−050835

0536015−050020

0536012−050158
0536012−050756

0535599−050430
0536003−050459
0536004−050553
0536007−045914
0536009−050848

0535592−045846
0535592−050733
0535595−051021
0535596−050128
0535596−050138
0535597−050643

0535588−051014
0535588−050026

0535587−045932

2MASS

265

decl.a−4:58:58.9−5:07:09.6−5:09:30.9−5:04:21.4−5:04:00.8−5:07:31.0−5:04:45.2−5:04:08.8−5:07:15.6−5:07:00.9−5:09:28.6−5:13:03.7−4:58:45.1−4:59:32.6−4:59:41.5−5:10:57.9−4:59:42.9−5:03:12.2−5:11:13.4−5:04:43.6−5:07:58.6−5:02:18.2−5:00:41.0−5:08:15.0−5:07:55.6

J bcd
15.71
17.39
15.66
16.59
14.81
17.73
16.74
12.77
10.90†
16.04
11.23>21.66
15.67
17.29
11.71
>21.41
11.75
15.35
13.78
16.45
15.62
14.63
14.92
15.81
>21.72

H bcd
14.73
16.55
14.86
15.69
14.03
16.81
15.73
12.02
10.57†
15.36
10.62†>20.71
14.73
16.02
11.20
>20.46
11.24
14.68
13.32
16.03
15.09
13.97
14.00
15.30
>20.77

K cd
14.49
16.44
14.70
15.32
13.85
16.54
15.51
11.67
10.51†
15.16
10.44†
16.61
14.39
15.72
11.13
16.14
11.16
14.55
12.88
14.15
14.69
13.77
13.77
15.19
17.05
0536054−050758
0536058−050218
0536059−050041
0536060−050815

0536050−045943
0536050−050312
0536051−051113

0536048−045845

0536045−050929

0536035−050445
0536041−050409
0536043−050715

0536032−050931
0536032−050421
0536034−050401

2MASS
0536031−045859

decl.a−5:09:40.1−5:06:07.4−5:03:06.9−5:06:15.5−5:08:50.8−5:04:07.6−5:04:15.4−5:09:41.2−5:09:37.3−5:04:01.8−5:06:14.7−5:01:41.3−5:04:34.3−5:02:32.2−5:02:35.0−5:02:26.3−5:00:49.9−5:05:35.3−5:07:02.7−5:06:12.3−5:04:34.0−5:02:31.3−5:03:41.2−5:00:32.4−5:00:53.8

J bcd
17.30
>21.91
17.24
12.98
16.68
16.98
17.67
16.28
17.23
14.68
17.02
15.28
15.97
18.70
15.94
17.84
13.48
14.23
15.51
17.79
15.85
15.50
8.44†
12.12
15.97

H bcd
16.32
>20.96
16.24
12.25
15.93
15.86
16.56
15.28
16.64
14.04
16.07
14.42
14.91
18.08
14.96
16.69
12.63
13.63
14.55
16.88
14.92
14.80
8.22†
11.37
14.73

K cd
16.03
17.47
16.06
12.04
15.93
15.61
16.43
15.07
16.72
13.97
15.90
14.30
14.70
16.34
14.70
16.44
12.53
13.39
14.36
16.83
14.84
14.71
8.14†
11.24
14.55
0536107−050434
0536108−050231
0536110−050341
0536118−050032
0536124−050053

0536098−050050
0536099−050535
0536101−050703

0536088−050235

0536085−050141
0536086−050434

0536082−050401

0536077−050941

0536067−050615
0536068−050851
0536070−050407

2MASS

upper limit of the magnitude).

d Saturated QUIRC magnitudes (brighter than 11 mag) are labeled < if they have no 2MASS counterpart, recognizing the value as the lower limit of the flux (thec Saturated QUIRC magnitudes (brighter than 11 mag) are replaced with 2MASS magnitudes and labeled † if they have the 2MASS counterpart.

b The upper limit of the flux (the lower limit of the magnitude) is given for sources with less than a 3 σ detection in the J, H, or both bands.

are truncated.

R.A.a
36:06.30
36:06.62
36:06.65
36:06.79
36:06.85
36:07.07
36:07.61
36:07.71
36:07.96
36:08.26
36:08.49
36:08.54
36:08.68
36:08.70
36:08.80
36:08.92
36:09.81
36:09.96
36:10.17
36:10.57
36:10.76
36:10.81
36:11.00
36:11.79
36:12.41

The hundredth and the tenth order in the arc seconds of R.A. and decl.

ID
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448

a The equinox in J2000.0 in the format of 05:mm:ss.ss for R.A. and dd:mm:ss.s for decl.

ID
R.A.a
1399 36:03.14
1400 36:03.21
1401 36:03.25
1402 36:03.29
1403 36:03.39
1404 36:03.53
1405 36:03.54
1406 36:04.15
1407 36:04.32
1408 36:04.48
1409 36:04.51
1410 36:04.70
1411 36:04.86
1412 36:04.87
1413 36:04.97
1414 36:05.07
1415 36:05.09
1416 36:05.09
1417 36:05.11
1418 36:05.43
1419 36:05.48
1420 36:05.87
1421 36:05.94
1422 36:06.02
1423 36:06.14(cont.)

266
APPENDIX B. QUIRC SOURCES AND 2MASS COUNTERPART

Acknowledgments
Without the support from my wonderful collaborators, this thesis could not have been completed. I am grateful to Katsuji Koyama who introduced me to the X-ray astronomy and to
the X-ray studies of star formation. I also appreciate Kensuke Imanishi in Kyoto University
and Yohko Tsuboi in Chuo University for their interesting discussions on X-ray emissions
from young stars.
For the NIR part of this work, I am particularly indebted to Naoto Kobayashi in NAOJ,
who instructed me in the infrared astronomy and oriented me to take a multi-wavelength
approach. Miwa Goto and Hiroshi Terada in NAOJ, and Alan T. Tokunaga in the Universityof Hawaii also helped me to obtain and analyze the NIR data and to publish results.
The radio part is based on my collaboration with Masao Saito in NAOJ and Claire
Chandler in NRAO, who gave me invaluable advice on the radio astronomy, interferometer
observations, data reductions, and publications.
I am obliged to all the staff members of various observatories that I visited for this work;
the Subaru telescope on September 8–30, 2000, November 27–December 27, 2000, and March
15–24, 2001, the University of Hawaii 88 inch (2.2 m) telescope on February 2–10, 2001 andMarch 10–14, 2001, and VLA on February 6–17, 2002. The observation using Subaru/IRCS
was conducted during its engineering time. Miwa Goto took me the L0 -band data at IRTF.
Michael Connelley spent a part of his observation time for our QUIRC calibration data. The
hospitality of all these people was the largest incentive for me to write the next observation
proposal.
My gratitude is also for Rolf Chini and Markus Nielbock who kindly offered me their
1.3 mm map of OMC-2 and OMC-3 including unpublished parts of their data, for Martin
Cohen who let me use his SKY model to estimate the galactic star count of our study field,
for Luisa M. Rebull who sent me the U V excess data of Orion sources, and for Hiroaki Isobe
267

268

ACKNOWLEDGMENTS

who gave me precious information on solar flares.
The members of my laboratory should be acknowledged as well for their continuous
encouragements. In particular, Hironori Matsumoto, Aya Bamba, and Junko Kushida helped
me to improve the manuscript through their critical proofreading and comments. Shigeo
Yamauchi in Iwate University also read the proofs. I would also like to thank Toru Tanimori,
Hideo Kodama, Shu-ichiro Inutsuka, and Hidetoshi Kubo for their constructive refereeing of
this thesis.
Finally, I express my most sincere appreciation to my thesis advisor, Professor Katsuji
Koyama, who mentored me throughout my graduate course. It is of my greatest honor that
I could start my career with fruitful five years under his gracious and thoughtful guidance.

This work is based on data collected at Subaru Telescope, which is operated by the
National Astronomical Observatory of Japan. The National Radio Astronomy Observatory
is a facility of the National Science Foundation operated under cooperative agreement by
Associated Universities, Inc. The Chandra data were obtained through the Chandra X-ray
Observatory Science Center (CXC) operated for NASA by the Smithsonian AstrophysicalObservatory. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing
and Analysis Center/California Institute of Technology, funded by the National Aeronautics
and Space Administration and the National Science Foundation. This research has madeuse of the Astronomical Data Center (ADC) at NASA Goddard Space Flight Center, andthe SIMBAD database operated at CDS, Strasbourg, France. This research has made useof NASA’s Astrophysics Data System Bibliographic Services. IRAF is distributed by the
National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science
Foundation.
I acknowledge financial support by the Japan Society for the Promotion of Science andthe Hayakawa Satio Foundation of the Astronomical Society of Japan.