星形成ゼミ 2015/ 8/7 Newsletter #271 No.21‒25
担当；清兼和紘•21. Pre- and Post-burst Radio Observations of the Class 0 Protostar HOPS 383 in
Orion
Galván-Madrid, Roberto; Rodríguez, Luis F.; Liu, Hauyu Baobab; Costigan, Gráinne; Palau,
Aina; Zapata, Luis A.; Loinard, Laurent
http://adsabs.harvard.edu/abs/2015ApJ...806L..32G•

22. A 1.3 cm line survey toward IRC +10216
Gong, Y.; Henkel, C.; Spezzano, S.; Thorwirth, S.; Menten, K. M.; Wyrowski, F.; Mao, R. Q.;
Klein, B.
http://adsabs.harvard.edu/abs/2015A%26A...574A..56G•

23. HNC in Protoplanetary Disks
Graninger, Dawn; Öberg, Karin I.; Qi, Chunhua; Kastner, Joel
http://adsabs.harvard.edu/abs/2015ApJ...807L..15G•

24. The Giant Molecular Cloud Environments of Infrared Dark Clouds
Hernandez, Audra K.; Tan, Jonathan C.
http://adsabs.harvard.edu/abs/2015arXiv150200183H•

25. Massive envelopes and ﬁlaments in the NGC 3603 star forming region
Hummel, C. A.; Stanke, T.; Galvan-Madrid, R.; Koribalski, B. S.
http://adsabs.harvard.edu/abs/2015arXiv150608597H
1

PRE- AND POST-BURST RADIO OBSERVATIONS OF THE CLASS 0 PROTOSTAR HOPS 383 IN ORION
Roberto Galván-Madrid1, Luis F. Rodríguez1,2, Hauyu Baobab Liu3, Gráinne Costigan4,
1
1
1
Palau
, Luis A. Zapataof, and• 21.1 Pre- and Post-burstAina
Radio
Observations
theLaurent
Class 0Loinard
Protostar HOPS 383 in Orion
Centro de Radioastronomía y Astrofísica, UNAM, Apdo. Postal 3-72 (Xangari), 58089 Morelia, Michoacán, México; r.galvan@crya.unam.mx
2
Astronomy
Department,
Faculty of Science,King
Abdulaziz
University,
P.O. Box
80203, Jeddah
21589, Saudi
ArabiaGalván-Madrid,Roberto;Rodríguez,
Luis F.;
Liu,
Hauyu
Baobab;
Costigan,
Gráinne;Palau,
Aina; Zapata,3
Academia Sinica, Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 106, Taiwan
4Luis A.; Loinard, Laurent
Leiden Observatory, University of Leiden, PB 9513, 2300 RA Leiden, The Netherlands
Received 2015 April 3; accepted 2015 May 30; published 2015 June 18

http://adsabs.harvard.edu/abs/2015ApJ...806L..32G (ApJ Letter)

ABSTRACT
There is increasing evidence that episodic accretion is a common phenomenon in Young Stellar Objects (YSOs).
Recently, the source HOPS 383 in Orion was reported to have a q35 mid-infrared—and bolometric—luminosity
increase between 2004 and 2008, constituting the ﬁrst clear example of a class 0 YSO (a protostar) with a large
accretion burst. The usual assumption that in YSOs accretion and ejection follow each other in time needs to betested. Radio jets at centimeter wavelengths are often the only way of tracing the jets from embedded protostars.
We searched the Very Large Array archive for the available observations of the radio counterpart of HOPS 383.
The data show that the radio ﬂux of HOPS 383 varies only mildly from 1998 January to 2014 December, staying at
the level of ∼200–300 μJy in the X band (∼9 GHz), with a typical uncertainty of 10–20 μJy in each measurement.
We interpret the absence of a radio burst as suggesting that accretion and ejection enhancements do not follow eachother in time, at least not within timescales shorter than a few years. Time monitoring of more objects and speciﬁc
predictions from simulations are needed to clarify the details of the connection betwen accretion and jets/winds
in YSOs.
Key words: ISM: jets and outﬂows – radio continuum: stars – stars: formation – stars: protostars
submillimeter-to-bolometric luminosity and in the characteristic temperature of the spectral energy distribution, Safron
The physical mechanisms of gas accretion and ejection are
et al. (2015) conclude that the object is a class 0 YSO, making
fundamental aspects in the paradigm of low-mass star
HOPS 383 the youngest protostar known with an accretionformation. In its most commonly assumed form, this paradigm
related burst. The outburst is most notably seen at a wavelength
requires the quasi-stationary evolution of the forming starsof 24 N m , in which the brightness increased by a factor q35(e.g., Shu et al. 1994). This assumption is seriously challenged
from 2004 to 2008. From their extensive IR to submillimeterby the observational evidence of episodic accretion. First, afollow up, Safron et al. (2015) ﬁnd no evidence for signiﬁcanthandful of individual bursting objects such as FU Ori and EX
fading of HOPS 383 up through 2012.
Lup provide evidence that large accretion bursts in YoungRadio observations are a key tool to study YSOs: the thermal
Stellar Objects (YSOs) do actually happen, with durations
free–free emitting radio jets are often the only way to probe thefrom a few months to ∼100 years (e.g., Hartmann &bipolar ejection of material close to the protostar in the
Kenyon 1996; Herbig 2008, Audard et al. 2014). Second,
optically obscured class 0 objects (e.g., Rodríguez 1997;
surveys show that YSOs are systematically underluminous with
Anglada et al. 1998). Radio observations are also useful torespect to the expectation of steady-accretion models (e.g.,
Evans et al. 2009; Kryukova et al. 2012). Episodes of 2 probe non-thermal (gyro)synchrotron radiation from active
YSO magnetospheres (e.g., Güdel 2002; Forbrich et al. 2007).
signiﬁcantly increased accretion would alleviate this discre1. INTRODUCTION

Table 1
Data SummaryEpoch15.01.1998
14.03.2008+01.06.2008
14.03.2008+01.06.2008
13.08.2011
13.08.2011
27.10.2014
03.11.2014
06.12.2014
13.12.2014
15.12.2014
All 2014

Frequency(GHz)

Array, HPBW, PA(arcsec × arcsec; deg)

Phase Center(h:m:s; deg:arcmin:arcsec)

HOPS383 Offset(arcsec)rms Noisea(μJy beam−1)

Flux Densityb
(μJy)

8.46
4.86
8.46
4.87
7.42
10.0
10.0
10.0
10.0
10.0
9.81

D; 9.2 q 7.5, −17.8
DnC+C; 6.0 q 4.2 , 49.8
DnC+C; 4.8 q 3.1, 57.4
A; 0.64 q 0.42 , −4.6
A; 0.44 q 0.27, −3.6
C; 2.18 q 1.66 , −1.9
C; 2.04 q 1.81, −7.2
C; 2.29 q 1.70 , −28.3
C; 2.35 q 1.61, −11.1
C; 2.28 q 1.65, −29.3
C, 2.32 q 1.62 , −14.1

05:35:24.395; −05:01:07.27
05:35:24.400; −05:01:43.25
05:35:24.413; −05:00:07.25
05:35:23.420; −05:01:30.52
05:35:23.420; −05:01:30.52
05:35:23.480; −05:01:32.30
05:35:23.480; −05:01:32.30
05:35:23.480; −05:01:32.30
05:35:23.480; −05:01:32.30
05:35:23.480; −05:01:32.30
05:35:23.480; −05:01:32.30

111.1
138.2
82.2
137.8
137.8
138.5
138.5
138.5
138.5
138.5
138.5

42
56
47
10
11
13
15
11
13
10
6

230 ± 50
224
188
270 ± 20310 ± 20
222 ± 12267 ± 16293 ± 13289 ± 15
246 ± 10260 ± 6

Notes.
arms noise corrected for primary-beam attenuation around the position of HOPS 383: B  5h 35m 29.s 81, E  4n59a51.´ 1 (Safron et al. 2015).
b
Flux density of HOPS 383 corrected for primary-beam attenuation. The errors are only statistical, resulting from the noise in the maps and the quality of the ﬁt. The
absolute uncertainty of the VLA ﬂux scale is a few percent (Perley & Butler 2013). Upper limits in the 2008 epoch are 4T .

free emission from radio jets and accretion signatures as seen in
the near- to mid-infrared. Bursting protostars offer a unique
opportunity to perform this test under different conditions in agiven object.
In this Letter, we report on pre- to post-burst centimeter
wavelength observations of the bursting class 0 YSOHOPS 383.
2. DATA SETS AND BASIC RESULTS

consider a detection. Our reanalysis of these data shows a faintsource with ﬂux density of 0.23 ± 0.05 mJy that coincides
spatially with HOPS 383.
2.2. 2008
These observations were made on 2008 March 14 and June 1
in the C and DnC conﬁgurations at 4.86 and 8.46 GHz as partof project AT359. The data from the two epochs wereconcatenated for increased sensitivy, but a counterpart to
HOPS 383 was not detected with a 4σ upper limit of 0.22 and0.19 mJy at 4.86 and 8.46 GHz, respectively.

To analyze the time behavior of HOPS 383 at centimeter
wavelengths, we looked for the available observations in the
Very Large Array5 archive. In none of these observations is2.3. 2011
HOPS 383 at the phase center; however, it falls inside the ﬁeldof view, allowing the determination of its parameters after
These observations were made on 2011 August 13 with thecorrection for the primary beam response. In the following
upgraded Jansky Very Large Array (JVLA) in the A
subsections we describe the observation epochs. Table 1
conﬁguration under project 11A-220. The tuning is centeredsummarizes the relevant properties of the data.
at 4.81 and 7.42 GHz, with total bandwidths of approximately
In all the epochs the position of the radio source matches
1 GHz. This is the only epoch with subarcsecond angularwithin 0″. 3–1″. 7 with the infrared position reported byresolution. The source associated with HOPS 383 is for the ﬁrst
Safron et al. (2015): B (J2000)  5h 35m 29.s 81, E (J2000) time resolved into two components (SE and NW) with a4n59a51.´ 1. This is a fraction of the synthesized beam in all the
separation of x0.´ 45 and joined by a ridge of faint emission. In
epochs in which the radio source appears unresolved (seemaps done with (u , v ) weighting close to natural, we measure
Table 1), and about the synthesized beam size for the 2011
ﬂux densities that are consistent with rest of the detections at
epoch with subarcsecond angular resolution.6 Since the next
other epochs: 0.27 ± 0.02 at 4.81 GHz and 0.31 ± 0.02 mJy at
closest radio detection is x120aa away, and the Spitzer-MIPS
7.36 GHz (see Table 1). The spectral index between theseangular resolution is _6aa, we conclude that the radio detection
frequencies is 0.3, indicating free–free emission with low
Regardless of the detailed jet emission mechanism, in thehere reported is the counterpart of the bursting protostar
optical depth. Figure 1 shows a map at 7.36 GHz done withmodelsit is assumed
an increaseof accretion
bydensity
Safron etal. (2015).
asreported
the ﬂux
fromthe concatenated data. There appear to weighting
betweennatural andthat
uniform
to maximize
angular is followedbyanejectionenhancement.
Therefore,
if
mid-IR burst
be marginal ﬂux variations within 2014. The maximal ﬂux resolution. The double nature of the radio source is theclearly
2.1.2014
1998December 12, which is 71 ± seen, probably
truly traces
ofradioaccretional.map2015), then adensity is 293 ± 13 μJy on
froma aburst
bipolarjet or a(Safron
binary. etThisthe radioalreadyﬂux should
the highest increase
angular in
resolution
suffersfollow.
from
18 μJythe minimalvalue
of 222± 12
onof2014 with signiﬁcant
Theseabove
observations
were madeon 1998
January
13 μJyas part)ﬂux
ﬁlteringofextendedemission.
signiﬁcant(
50%that in HOPS 383 the infrared burst does not have a
We_ﬁndOctober
27.AR387.
Then, The
without
considering
the few andpercent
the project
analysishas been presented
counterpart
in the3
radio. Figure 2 shows the radio light curves.
uncertainty
the absolute
ﬂux scale(Perley& Butlerat2013),
discussed in in
Reipurthet al. (1999).
The data
were obtaineda2.4. 2014 radio ﬂux densities show mild
The long-term (decadal)
frequency of 8.46 GHz in the D conﬁguration. Reipurth et al.

1•

Purple Mountain Observatory & Key Laboratory for Radio Astronomy, Chinese Academy of Sciences, 2 West Beijing Road,
210008 Nanjing, PR China
22. A e-mail:1.3 cmline survey toward IRC +10216
ygong@pmo.ac.cn
2
Max-Planck Institute für Radioastronomy, Auf dem Hügel 69, 53121 Bonn, Germany
Gong,3 University
Y.; Henkel,
C.;Academy
Spezzano,
S.;No.
Thorwirth,S.; 100049
Menten,of Chineseof Sciences,
19A Yuquan Road,
Beijing,K.
PR M.;
ChinaWyrowski, F.; Mao, R. Q.;
4
Astronomy Department, King Abdulaziz University, PO Box 80203, 21589 Jeddah, Saudi Arabia
Klein,5 B.
I. Physikalisches Institut, Universität zu Köln, 50937 Köln, Germany
6
University of Applied Sciences Bonn-Rhein-Sieg, Grantham-Allee 20, 53757 Sankt Augustin, Germany

http://adsabs.harvard.edu/abs/2015A%26A...574A..56G (A&A)
Received 15 August 2014 / Accepted 19 November 2014

ABSTRACT

Context. IRC +10216 is the prototypical carbon star exhibiting an extended molecular circumstellar envelope. Its spectral properties
are therefore the template for an entire class of objects.
Aims. The main goal is to systematically study the λ ∼ 1.3 cm spectral line characteristics of IRC +10216.
Methods. We carried out a spectral line survey with the Eﬀelsberg-100 m telescope toward IRC +10216. It covers the frequency range
between 17.8 GHz and 26.3 GHz (K-band).
Results. In the circumstellar shell of IRC +10216, we find 78 spectral lines, among which 12 remain unidentified. The identified lines
are assigned to 18 diﬀerent molecules and radicals. A total of 23 lines from species known to exist in this envelope are detected forthe first time outside the solar system and there are additional 20 lines first detected in IRC +10216. The potential orgin of “U” lines isalso discussed. Assuming local thermodynamic equilibrium (LTE), we then determine rotational temperatures and column densitiesof 17 detected molecules. Molecular abundances relative to H2 are also estimated. A non-LTE analysis of NH3 shows that the bulkof its emission arises from the inner envelope with a kinetic temperature of 70 ± 20 K. Evidence for NH3 emitting gas with higher
kinetic temperature is also obtained, and potential abundance diﬀerences between various 13 C-bearing isotopologues of HC5 N are
evaluated. Overall, the isotopic 12 C/13 C ratio is estimated to be 49 ± 9. Finally, a comparison of detected molecules in the λ ∼ 1.3 cm
range with the dark cloud TMC-1 indicates that silicate-bearing molecules are more predominant in IRC +10216.
Key words. astrochemistry – ISM: molecules – stars: individual: IRC +10216 – radio lines: stars

・IRC+10216[AGB carbon star]の星周シェル(circumstellar shell)での1.3cm帯 (17.8 - 26.3 GHz)のラインサーベイ1. Introduction
manner. In addition, complex molecules have small rotational
constants so that their lowest-energy transitions arise at cm・結果；78輝線(12未同定輝線；18{異なる分子あるいはラジカル}；23輝線はこのエンベロープで存在がMolecular line surveys
are a powerful tool for analyzing both wavelenths. In this way, emission or absorption features fromphysical and chemical parameters of astronomical objects. In long carbon-chain molecules can be observed (e.g. HC N,
3
知られている分子種で太陽系の外で初検出、さらに20輝線はIRC+10216で初検出。
fact, they are the only means of obtaining a complete, unbiased HC N, HC N, HC N). Since systematic and highly sensitive
5
7
9
view
of the molecular inventory of a given source. However, de- surveys at these (low) frequencies that cover diﬀerent sources
・未同定輝線に関しては可能性を議論。
spite the long history of powerful large radio telescopes, few un- have rarely been carried out, one can only speculate as to what
・17分子でrotationaltemperaturaとcolumn
biasedfrequency surveys have been
conducted in the cm-wave densityを計算。
else may be observed. The enormous potential of cm-wave asregime.
A
4.4
GHz
bandwidthsurvey
from
17.6
to
22.0
GHz
totronomy for detecting new molecules in space has been high・H2に対する分子の存在比を見積もった。
ward the massive star-forming region W51 has been reported by lighted in the recent past through GBT detections of complex or・NH3のnon-LTE
temperatureの内側のエンBellet al. (1993b) showinganalysisにより、その放射の大半が70+-20Kのkinetic
many previously unidentified lines. ganic molecules such as CH CHCHO(propenal), CH3 CH2 CHO
2The dark cloud TMC-1 has been observed in selected bands (propanal), and CNCHO (cyanoformaldehyde; Hollis et al.
ベロープに起因することを示した。HC5Nの様々な13C同位体の間に存在比の違いを評価した。全般的に、from 4−6 and 8−10 GHz (Kalenskii et al. 2004), as well as at
2004; Remijan et al. 2008).
9−50
GHz(Kaifuetal.
2004).
More
recently,somesystematic
12C/13C比は49+-9と推定された。
For this paper, we performed a 1.3 cm line survey toward
observations toward the galactic center have also been reported
by・最後に、1.3cm帯の検出された分子に着いてTMC-1との比較を行い、IRC+10216でSi系分子がよRemijan et al. (2008) in the course of their GBT PRIMOS IRC +10216, which is also known as CW Leonis. It is found tobe the brightest object outside the solar system at 5 µm (Becklin
project1 .
り多いこと示した。
4
branch (AGB)
Spectroscopic features that are expected at long wavelengths et al. 1969). It is a well-studied asymptotic giant −5−1Table 1; これまでのIRC+10216でのLine surveyの研究；今回の観測周波数帯域は十分に調べられてきていない。

carbon chain molecule (eg. HC5N)の低励起輝線が多く検出された。またこれらの13C同位体も検出された。23輝線は太陽系外で初検出で、20輝線(13C同位体の炭素鎖分子など)はこの天体で初検出。（これらの輝線の幾つかは他の周波数帯ですでに検出されている）

5

柱密度とTrotを求めた
・Trot; 5.5 - 47.2 K
・N; 5.2E12 - 2.4E15 cm^-2!
例えばc-C3H2は最も低いTrotを持
つがそれは外側の冷たいエンベロー
プに存在することを示唆する。

!
Nはより複雑な分子で低い存在比の傾向がある。

ー＞ﬁg 5; IRC+10216とTMC-1の比較；
IRC+10216はSi系分子が多く存在する
6

HNC IN PROTOPLANETARY DISKS
Dawn Graninger1, Karin I. Öberg1, Chunhua Qi1, and Joel Kastner2

1• 23. HNC
in Protoplanetary
Disks
Harvard-Smithsonian
Center for Astrophysics,
60 Garden Street, Cambridge, MA 02138, USA; dgraninger@cfa.harvard.edu
2Center for Imaging Science, School of Physics and Astronomy, and Laboratory for Multiwavelength Astrophysics, Rochester Institute of Technology,
Graninger, Dawn; Öberg, KarinI.; Qi,
Chunhua;
Kastner,Joel USA
54 Lomb
Memorial
Drive, Rochester,
NY 14623,
Received 2015 February 19; accepted 2015 May 28; published 2015 July 1

http://adsabs.harvard.edu/abs/2015ApJ...807L..15G (ApJ Letter)
ABSTRACTThe distributions and abundances of small organics in protoplanetary disks are potentially powerful probes of disk
physics and chemistry. HNC is a common probe of dense interstellar regions and the target of this study. We use
the Submillimeter Array (SMA) to observe HNC 3–2 toward the protoplanetary disks around the T Tauri star
TW Hya and the Herbig Ae star HD 163296. HNC is detected toward both disks, constituting the ﬁrst spatiallyresolved observations of HNC in disks. We also present SMA observations of HCN 3–2 and IRAM 30 m
observations of HCN and HNC 1–0 toward HD 163296. The disk-averaged HNC/HCN emission ratio is 0.1–0.2
toward both disks. Toward TW Hya, the HNC emission is conﬁned to a ring. The varying HNC abundance in the
TW Hya disk demonstrates that HNC chemistry is strongly linked to the disk physical structure. In particular, theinner rim of the HNC ring can be explained by efﬁcient destruction of HNC at elevated temperatures,
similar to what is observed in the ISM. However, to realize the full potential of HNC as a disk tracer requires a
combination of high SNR spatially resolved observations of HNC and HCN and disk-speciﬁc HNC chemical
modeling.
Key words: astrochemistry – ISM: molecules – protoplanetary disks
1. INTRODUCTION
The disks around young stars contain the gas and dust fromwhich planets form. From theory (Aikawa et al. 1996; Bergin
et al. 2003) and observations (Rosenfeld et al. 2012; Qi
et al. 2013a), disks are characterized by steep temperature andradiation gradients both radially and vertically. These disk
structures affect planet formation (Takeuchi et al. 1996; Kretke& Lin 2012), motivating the quest for new emission-line
diagnostics that can trace physical structure gradients in disks.
This study focuses on HNC, a common high-density gas
tracer in the ISM. At low temperatures, HNC forms efﬁciently
together with HCN through ion–molecule reactions. HNC and
HCN are observed in a variety of different sources, but theirrelative abundances can vary by more than an order ofnitrogen reservoir. Cyanides and iso-cyanides are also
important for some prebiotic chemistry scenarios (Powner
et al. 2009). Observing HNC in disks has proven challenging,
however. The intrinsic disk scales are small and the molecularline ﬂuxes are weak compared to interstellar clouds andprotostars. To date, HNC has only been detected in a single
disk, DM Tau (Dutrey et al. 1997), and no spatially resolved
observations exist.
In this Letter, we report the ﬁrst interferometric detection of
HNC in two disks, around the T Tauri star TW Hya(D = 54 pc; Qi et al. 2004) and the Herbig Ae star HD
163296 (D = 122 pc; Qi et al. 2011), using the Submillimeter
Array (SMA). We combine these observations with new andprevious SMA observations of HCN toward TW Hya and HD
163296 and new IRAM 30 m observations of HNC and HCN

Graninger et al.

Figure 1. 1.1 mm continuum and HNC 3–2 emission (upper panels) from TW
Hya using the compact + extended conﬁgurations of the SMA. Continuum
contours are [10, 20, 40,K] mJy, and the contours for HNC are [4, 6, 8]σ with
1σ = 0.064 Jy km s−1 beam−1. The lower left panel displays the spectrum
obtained from the HNC 3–2 image. The lower right panel displays the
deprojected, azimuthally averaged ﬂux as a function of radius.

TW Hya disk. This agrees with the ∼1″ separation between thetwo ﬂux peaks in the HNC-integrated emission image. The
depth and size of the hole may both be affected by the image
asymmetry, however. In Section 3.2, we evaluate the evidenceof an HNC ring and quantify its location based on an analysis
in the (u , v ) plane.
The HNC spectrum in Figure 1 was extracted using a
2.´ 5 q 2.´ 5 box. The integrated line ﬂux is 1.2 Jy km s−1 beam−1(∼12σ). Using the integrated HNC ﬂux from this study and theHCN ﬂux from Qi et al. (2008), the disk-averaged HNC/HCN
emission ratio is 0.18 ± 0.06, where the error is derived using the1σ rms for the two observations.
HNC is also detected toward HD 163296, but with a lower
SNR. Figure 2 displays the 1.1 mm continuum, HNC, and
HCN emission toward HD 163296, as well as the spectra andspatial velocity structure of emission from these molecules. The
velocity-integrated emission maps yield a maximum HNC andHCN ﬂux of 0.71 and 2.71 Jy km s−1 beam−1, respectively. The
HNC emission toward the HD 163296 disk is suggestive of aring viewed at a relatively high inclination, but the low SNR
inhibits any further spatial analysis.
Spectra were extracted using an elliptical mask, which
increased the SNR compared to a square mask. The total
integrated ﬂux from these spectra is 0.66 Jy km s−1 beam−1(∼4σ) and 4.47 Jy km s−1 beam−1 (∼9.5σ) for HNC and HCN,
respectively. This yields an HNC/HCN ratio of 0.14 ± 0.05,
similar to TW Hya.
The IRAM 30 m observations of HNC and HCN 1–0 toward
HD 163296 should be more sensitive to the coldest disk
material (Figure 3). The integrated intensities of HNC and
HCN were found to be 0.033 K km s−1 (3σ upper limit) and
0.104 K km s−1, respectively. This yields an upper limit on the
HNC/HCN ratio of 0.3, consistent with the SMA data.

3.2. HNC Line Modeling toward TW Hya
To constrain the spatial extent of the HNC emission in TW
Hya, we follow the procedure outlined in Qi et al. (2008) andÖberg et al. (2012, 2015) to extract molecular column density
proﬁles. First, parametric HNC abundance models are deﬁned
with respect to the TW Hya disk temperature and density
structures from Qi et al. (2013b). The line emission is modeledusing the two-dimensional non-LTE Monte Carlo radiativetransfer code RATRAN (Hogerheijde & van der Tak 2000)
using collisional cross-sections from Dumouchel et al. (2010).
The HNC abundance models follow the form in Qi et al.
(2008), which assumes a molecular layer with a vertically8

constant abundance, bound by surface (Ts) and midplane (Tm )boundaries deﬁned with respect to the vertically integratedhydrogen column in units of 1.59 × 1021 cm−2. We set the HNC
boundaries using the values from Qi et al. (2008) for HCN (log
Ts = −0.5, log Tm = 1.5). The radial distribution of HNC wasmodeled using an abundance power law with an outer radius(Ro), hole radius (Rh), and power-law index of −1.5. The
parameter Ro was varied between 35 and 60 AU and Rh wasvaried between 20 and 50 AU. The minimum D 2 value wascalculated from the modeled and observed HNC emission inthe (u , v ) plane using the data from the compact and extended
conﬁguration.
Figure 4 shows examples of emission models and observations in the extended conﬁguration. The best-ﬁt model based on
the D 2 value is a 10 AU wide ring with an Ro of 45 AU and an
Rh of 35 AU (Figure 5), shown in the lower left panel of
Figure 4. This model results in no signiﬁcant residuals whensubtracted from the data in the (u , v ) plane and then imaged.
The observed HNC azimuthal asymmetry toward TW Hya isthus not signiﬁcant. The presence of an HNC ring in the TW
Hya disk is by contrast a statistically signiﬁcant result. Figure 5
shows the models that ﬁt the data within 2σ and 3σ. Within 2σ,
the hole size is 28–45 AU (3σ: 26–47 AU), and the outer edge
is at 37–55 AU (3σ: 57 AU).
4. DISCUSSION
In this study, we detect and spatially resolve HNC emission
toward TW Hya and HD 163296. From these observations, we
extracted disk-averaged HNC/HCN emission ratios and theinner and outer HNC emission radii in the TW Hya disk. Here,we will discuss the constraints that these observations provideon the HNC chemistry and the disk structure.

First, HNC and HCN are not co-spatial—some HCN ispresent toward the center of the disk, where HNC is absent.
This may be partially mitigated by averaging the HNC and
HCN emission only across disk areas where HCN and HNCemission are respectively detected. Second, the relationshipbetween line emission and abundance ratios is complicated byhigh HCN line opacities and different HCN and HNC
excitation properties (Sarrasin et al. 2010). We used the large
velocity gradient radiative transfer code, RADEX (van der Tak
et al. 2007), with the collisional rate constants from Dumouchel
et al. (2010) to evaluate the relationship between the
HNC/HCN line emission and the abundance ratios using
temperatures and densities characteristic of HCN disk emission(Walsh et al. 2010) and the HCN column density from Qi et al.
(2008). We ﬁnd that the line and abundance ratios can differ by
up to an order of magnitude, demonstrating that more detailed
modeling is required to extract HNC/HCN abundance ratiosfrom the observed line emission.
Even if abundance ratios are successfully extracted, it may
be difﬁcult to infer a characteristic emission region temperature. Other environmental characteristics than temperature may
regulate the HNC/HCN abundance ratio in disks. The model by
Graninger et al. (2014) neglects the inﬂuence of radiation,
which is reasonable in cloud cores, but may not be a good
approximation in disks (Meijerink et al. 2007). Loison et al.
(2014) have also shown that the HNC/HCN ratio depends on
the C/O ratio, which may be elevated in disks. In the absence ofdetailed disk chemistry models that incorporate the complete
HNC/HCN chemistry, disk-averaged line ratios are thus notuseful probes of disk properties.
4.2. The HNC Inner and Outer Radii in the TW Hya Disk
In the disk toward TW Hya, there is a lack of HNC emissioninterior to 28–45 AU, corresponding to temperatures above
21–13 K using the Qi et al. (2013b) temperature proﬁle. HCN
does not have an emission hole (Qi et al. 2008). The observed
absence of HNC close to the star is consistent withtemperature-dependent
HNC
destruction(Graninger
et al. 2014). It is difﬁcult to explain the hole with the increased
UV ﬂux present at smaller radii since HNC and HCN arethought to have similar photodissociation cross-sections(Roberge et al. 1991; van Dishoeck et al. 2006).
HNC also has an outer emission radius between 35 and
55 AU, with the best ﬁt at 45 AU, substantially smaller than theobserved radii of other gases, including CO, HCO+, and HCN(Qi et al. 2008). This outer cutoff in HNC emission was
unexpected. It coincides
with the onset of C2H emission, which9
is proposed to be a UV photochemistry product (Kastner•議論[memo;HNCについて]・prestellerやprotostellerの環境 (10K)では、HNC/HCN ~ 1
温度が上がるとHNC/HCNの比は小さくなる＝＞HNC/HCNの比は温度を反映する
・低い温度でもC原子(H原子?)によりHNCは破壊される・shieldがあまりされていない領域では放射により破壊される (UV)!
[inner radii]
・HCNはHNCより内側までいる。
HNCの内縁は28-45AUで、Qi+2013bによる温度分布では21-13Kであり、HCNが破壊される温度と一致する。[温度が>25Kより大きいところで、HNCは効率的に破壊される][photodissociationでは、HCNとHNCが異なる内縁半径を持つことを説明できない][outer radii]
・HNCの外縁半径は35-55AU (best ﬁt:45AU)で、COやHCO+, HCNで観測されている半径よりもかなり小さい・他の観測では、C2Hでも同様に見られ、UV photochemistryによるものと示唆されている
また、dustの密度の急激な減少している半径と近い
これらのことからHNCの外縁半径について以下の三つの可能性が考えられる。
(1). HNCのUV photodissociation (外縁部では柱密度が小さく、星や星間のUVが入ってくる)(2). H2とC系のUV photodissociation の増加で、HNC+H, HNC+Cの破壊反応が促進される(3). gasとdustが低密度のため、grain-gas thermal decoupling が生じていて、HNCが高い温度となり破壊反応が進んでいる(内縁と同じ機構)。
＝＞これらを切り分ける為には空間的に分離し高いSNRの観測(ALMA)とHNC/HCNの円盤に特化した化学モデルが必要である

!
!

10

:1502.00183v3 [astro-ph.GA] 18 Jun 2015

Audra K. Hernandez
Department of Astronomy, University of Wisconsin, 475 North Charter Street, Madison, WI 53706, USA;
hernande@astro.wisc.edu•

24. The Giant Molecular Cloud Environments of Infrared Dark Clouds
Jonathan C. Tan

Hernandez, Departments
Audra K.;
Tan, Jonathan
of Astronomy& Physics, C.
University of Florida, Gainesville, FL 32611, USA;jt@astro.ufl.edu

http://adsabs.harvard.edu/abs/2015arXiv150200183H(ApJ)
Draft version June 19, 2015
ABSTRACT
We study Giant Molecular Cloud (GMC) environments surrounding 10 Infrared Dark Clouds(IRDCs), using 13 CO(1 0) emission from the Galactic Ring Survey. We measure physical propertiesof these IRDCs/GMCs on a range of scales extending to radii, R, of 30 pc. By comparing di↵erent
methods for defining cloud boundaries and for deriving mass surface densities and velocity dispersions,
we settle on a preferred “CE,⌧ ,G” method of “Connected Extraction” in position-velocity space plus
Gaussian fitting to opacity-corrected line profiles for velocity dispersion and mass estimation. We
examine how cloud definition a↵ects measurements of the magnitude and direction of line-of-sightvelocity gradients and velocity dispersions, including associated dependencies on size scale. CE,⌧ ,Gdefined GMCs show velocity dispersion versus size relations / s1/2 , which are consistent with thelarge-scale gradients being caused by turbulence. However, IRDCs have velocity dispersions thatare moderately enhanced above those predicted by this scaling relation. We examine the dynamical
state of the clouds finding mean virial parameters ↵¯ vir ' 1.0 for GMCs and 1.6 for IRDCs, broadly
consistent with models of magnetized virialized pressure-confined polytropic clouds, but potentiallyindicating that IRDCs have more disturbed kinematics. CE,⌧ ,G-defined clouds exhibit a tight correlation of /R1/2 / ⌃n , with n ' 0.7 for GMCs and 1.3 for IRDCs (c.f., a value of 0.5 expected for a
population of virialized clouds). We conclude that while GMCs show evidence for virialization overa range of scales, IRDCs may be moderately super virial. Alternatively, IRDCs could be virialized
but have systematically di↵erent 13 CO gas phase abundances, i.e., due to freeze-out, a↵ecting massestimations.
Subject headings: ISM: clouds - ISM: kinematics and dynamics - Stars: formation
1. INTRODUCTION

Galactic star formation resides mostly within Giant Molecular Clouds (GMCs), conventionally defined to have masses
104 M and observed to extend up to several ⇥106 M (e.g., Blitz 1993; Williams et al. 2000; McKee & Ostriker2007). With typical mass surface densities of ⇠ 100 M pc 2 , GMCs have mean radial sizes of ⇠ 6 100 pc, assuming
simple circular symmetry. However, GMCs are highly irregular and hierarchical structures. Their dense clumps canspawn stellar clusters and associations, creating the bulk of the Galactic field star population. The efficiency and rateof star formation from these clumps is relatively low, i.e.,11a few percent per local free-fall time (Zuckerman & Evans
1974; Krumholz & Tan 2007). This appears to be mostly because much of the GMC material is stable with respect to

80

0.00

60
28.8

28.5

28.8

l

95
90
85
80
75
70

1.5
1.0

K deg

100

vlsr (km s−1)

I [K km s−1]

E

b

0.25

120

0.5
0.0

28.5

28.8

l

28.5

0.0

l

0.2

28.8

b

28.5

0.0

l

0.2
b

Fig. 1.— The IRDC/GMC sample: each row presents a single cloud (A through E) showing data out to a radius of 30 pc. Left to right:
GLIMPSE 8 µm image with the IRDC boundary marked with a pink ellipse (see Figs. 3 and A1-A4 for intensity scales); 13 CO(1-0) GRS
integrated intensity map (over the range v0 ± 15 km s 1 ) in units of K km s 1 ; Full projections of the cloud in position-velocity space:
simple-extraction (SE) 13 CO(1-0) vlsr vs l map, SE 13 CO(1-0) vlsr vs b map; connected extraction (CE) 13 CO(1-0) vlsr vs l map; CE
13 CO(1-0) v
lsr vs b map. The IRDC is marked with a white box of width equal to the extent of the elliptical boundary and height equal
to the FWHM of the IRDC co-added spectra. The solid black line shows the mass-weighted linear velocity gradient (dv0 /ds) across eachcloud at R = 30 pc.

3. METHODS: DERIVATIONS OF MOLECULAR CLOUD PROPERTIES
3.1. Definition of Cloud Boundaries
物理量を導出するのにいくつかの領域を選定する方法を試した(Table2)
We
firstsimple
determinedthe cloudcenter-of-mass in position-velocity space. To do this, we co-added the 13 CO spectra
・SE;
extraction(領域内の13COemissionをすべて使う）
within an elliptical boundary defined by twice the rmaj and rmin values, using the full GRS velocity range. Then, a
領域サイズを5,10,20,30pcと変化。
velocity intervalof 30 km s 1 was considered, centered on the peak of the emission profile. The cloud’s center-of-mass
was・CE;evaluatedfor both extraction
optically thinand opacity corrected gas, (l0 , b0 , v0 ) and (l0,⌧ , b0,⌧ , v0,⌧ ), respectively. We thenconnected(PV上で繋がっている領域のみを使う）；
use this as the reference point around which to search for GMC-scale gas, out to a projected radius of 30 pc and over a
抽出された領域で平均質量半径,領域半径、半分の質量半径で計算。
new velocity
range of v0 ± 15 km s 1 . This range is wide enough to sample the velocities of GMC gas, even those thatare potentially undergoing collisional interactions at velocities set by Galactic shear at the tidal radii of the clouds(Tan 2000; Tasker & Tan 2009). The GLIMPSE 8µm and GRS 13 CO integrated intensity maps centered on theselocations are presented in Figures 1 and 2.
We examined 13 CO emission within the v0 ± 15 km/s velocity range and within apertures of varying radii from thecloud center-of-mass coordinate. To explore how boundary definitions a↵ect estimated physical properties, we used
two di↵erent methods to select 13 CO line emission associated with the cloud. First, “Simple Extraction (SE)” selected
TABLE 2
GMC Physical Parameters Estimates
IRDC
Case

lCM ,lCM,⌧

bCM ,bCM,⌧

vCM ,vCM,⌧
1)

(pc)

(

)

( )

( km s

(1)

(2)

(3)

(4)

5

18.856,18.868-0.282,-0.276

64.3,64.3

10

18.862,18.875-0.282,-0.282

63.9,64.1

20

18.868,18.881-0.301,-0.313

63.5,63.7

30

18.868,18.881-0.307,-0.319

RM

18.881,18.893

RA

18.881,18.893

R1/2

18.881,18.893

s

v

R
1)

(pc)

M ,M⌧ ,MG
⇥104

(pc)

( km s

(M

(5)

(6)

(7)

(8)

2.06,2.12

0.0,0.0

5.00

2.58,2.57-0.4,-0.2

10.0

3.46,4.02-0.9,-0.6

62.6,63.1

3.72,4.37-0.325,-0.337

63.3,63.5-0.325,-0.337

63.3,63.5-0.325,-0.337

63.3,63.5), ⌧, G( km s1)

dv0 dv0,⌧
,
ds
ds
⇥10 2

✓v ,✓v,⌧

I0 ,I0,⌧⇥103

Erot,0 ,Erot,0,⌧
⇥1046

(M

pc2 )

,
(10

⌧
2)

log(↵vir ),log(↵vir,⌧ ),log(↵vir,G )(km/s/pc)

(deg)

(erg)

(9)

(10)

(11)

(12)

(13)

(14)

(15)

1.10,1.87,1.62

3.92,3.48,1.66

36.0,32.3

141,1240.0814,0.131

1.37,4.01

7.62,3.39

0.912,0.575,-0.00704

4.83,7.20,5.73

5.12,4.53,1.94

15.2,16.1

124,123

1.36,1.97

13.3,29.6

2.34,1.72

0.802,0.521,-0.115

20.0

16.1,24.0,19.2

5.87,5.15,2.36

16.8,15.6

139,142

16.8,25.7

74.2,165

6.38,3.78

0.696,0.411,-0.170-1.7,-1.3

30.0

31.0,44.1,34.9

6.58,6.01,3.02

12.7,12.1

96.8,96.3

68.2,96.7

183,370

5.97,3.80

0.688,0.457,-0.0389

5.10,6.60-1.7,-1.3

17.4,17.0

9.63,16.7,15.7

3.38,2.88,2.00

17.5,14.0

151,153

7.63,12.9

30.5,94.2

7.67,2.69

0.380,-0.00984,-0.298

5.10,6.60-1.7,-1.3

26.6,26.6

16.6,28.7,26.9

3.88,3.36,2.33

16.5,14.0

133,134

32.3,54.3

59.3,177

14.8,5.97

0.447,0.0862,-0.204

5.10,6.60-1.7,-1.3

17.1,16.2

9.38,15.5,14.7

3.34,2.81,1.99

17.2,13.5

151,153

7.18,11.0

29.4,84.9

7.18,2.36

0.374,-0.0177,-0.291

A

B

12

IRDC
A
B
C
D −s
E
F −s
G −s
H −s
I
J

1.5
1.0
0.5
0.0

GMC

−0.5
1.5
1.0
0.5
0.0
−0.5
1.5
1.0
0.5
0.0
−0.5
−0.5

0.0

0.5

1.0

1.5

−0.5

0.0

0.5

1.0

1.5

13

1

European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany ???
2
Centro de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Morelia 58090, Mexico
25. Massive envelopes and ﬁlaments in the NGC 3603 star forming region
3•
CSIRO Astronomy and Space Science, Australia Telescope National Facility, P.O. Box 76, Epping, NSW 1710, Australia

Hummel, C. A.; Stanke, T.; Galvan-Madrid, R.; Koribalski, B. S.
http://adsabs.harvard.edu/abs/2015arXiv150608597H (A&Ap)

1506.08597v1 [astro-ph.SR] 29 Jun 2015

Received: <date>; accepted: <date>; LATEXed: June 30, 2015

ABSTRACTThe formation of massive stars and their arrival on the zero-age main-sequence occurs hidden behind dense clouds of gas and dust. In
the giant H ii region NGC 3603, the radiation of a young cluster of OB stars has dispersed dust and gas in its vicinity. At a projecteddistance of 2.5 pc from the cluster, a bright mid-infrared (mid-IR) source (IRS 9A) had been identified as a massive young stellar
object (MYSO), located on the side of a molecular clump (MM2) of gas facing the cluster. We investigated the physical conditions
in MM2, based on APEX sub-mm observations using the SABOCA and SHFI instruments, and archival ATCA 3 mm continuum andCS spectral line data. We resolved MM2 into several compact cores, one of them closely associated with IRS 9A. These are likely
infrared dark clouds as they do not show the typical hot-core emission lines and are mostly opaque against the mid-IR background.
The compact cores have masses of up to several hundred times the solar mass and gas temperatures of about 50 K, without evidence
of internal ionizing sources. We speculate that IRS 9A is younger than the cluster stars, but is in an evolutionary state after that of thecompact cores.
Key words. stars: circumstellar matter - stars: early-type - stars: formation - stars: pre-main sequence - stars: individual: NGC 3603
IRS 9A・giant HII region であるNGC3603の隣の molecular clump (MM2)に対して、
APEX sub-mm Obs (SABOCA and SHFI)ATCA 3mm continuum and CS spectral line data
1. Introduction
disk, being photo-evaporated by a newly formed O star if one
considers the emission lines seen in a MIR Spitzer spectrum ofを用いて調べた。
The formation of high-mass stars is rapid (Zinnecker & Yorke IRS 9A (Lebouteiller et al. 2008). Adopting the distance to the・MM2の周辺環境としては、OBstarsの若いクラスターの放射によってガスやダストが晴らされていて2007) and leaves the new-born star
still enshrouded in gas and cluster, 7.2 kpc (Melnick et al. 1989) for the distance to MM2
クラスターから2.5pc(projected)に明るいmid-IR
9A)；massive young stellarが存在し、dust. Unlike the formationof low-mass stars viasource
simple (IRS
accreand IRS 9A (see also the discussion in de Pree et al. 1999), 1"
tion
disks,
theoreticalstudiesshow
thatfilaments
andnonaxIRS 9AはMM2の隣に位置している。
corresponds to 7200 AU.
isymmetricdisks(Krumholz
et
al.
2009)
that
funneltheradia・結果として、MM2を幾つかのcompact coresに分解し、そのうちの一つはIRS9Aの近くに付随していtive flux into the polar directions (Kuiper et al. 2015) provide
る。
protection for the accreting gas against the uniquely intense stel・これらはinfrared dark cloudである、（これらは典型的なhot-core emission lineを持たない）
lar radiation pressure until the final mass has been reached.
The (virial)sourceの兆候は見ら
mass of the molecular clump MM2 was deter・そのcompact
coresは数100Msunの質量を持ち、温度は〜50K(内部にionizing
Looking forcandidate massive young stellar objects

mined by Nürnberger et al. (2002) from observations of CS lines

れない)である。
(MYSO) suitable for observation due to low foreground extinc- to be around 1500 solar masses. Due to the close association
tion, Nürnberger (2003) identified a bright infraredcoresより進化段階が進んでいると推量される
source (IRS of the MYSO IRS 9A and MM2 we performed observations at
・IRS9Aはクラスターの星よりも若いが、compact

9A: Frogel et al. 1977), on the side of a molecular clump (MM2: sub-mm radio wavelengths to penetrate the obscuring dust and to
Nürnberger et al. 2002) facing a massive cluster of OB stars at14determine total dust masses and physical conditions in the emisthe center of the H ii region NGC 3603. Nürnberger (2003) esti-

15