An X-ray study of two
Green Pea galaxies
T. Kawamuro (NAOJ)
SDSS J0749+3337

SDSS J0822+2241

Y. Ueda (Kyoto Univ.), K. Ichikawa (Tohoku Univ.),
M. Imanishi, T. Izumi (NAOJ), A. Tanimoto (KyotoUniv.) and K. Matsuoka (Ehime Univ.)

The 6th Galaxy Evolution Workshop(TK+, submitted to ApJ)

Science BG: Seed black holes for SMBHs
What is the main process that forms seed black holes?
+ The remnant of massive Population III stars+ The result of the direct collapse of primordial dense gas+ The end-product of very massive stars formed through stellar mergers
in dense star clusters(http://www2.iap.fr/users/volonter/BHformation.html)

BH occupation fraction+ The current sample is biased
against heavily obscuredsystems.

Fraction of galaxies with black holes+ The BH occupation fraction REVIEW
has information of seed BHs.
+ The fraction is1(#AGN/fagn)/#all galaxies(fagn = 0.1: active BH fraction)+ A lower fraction favors thedirect collapse scenario
as a primary process.

Theory: Stellar death

Theory: Direct collapse

0.5Di0108tcrelocsieovfa?
drespla1091010

M gal (M )(soft X-ray study by Greene 12)

Figure 2 | The Occupation Fraction. We show the expected fraction10

BH occupation fraction

No. 6, 2010

THE WIDE-FIELD INFRARED SU+ The BH occupation fraction
has information of seed BHs.
+ The fraction is(#AGN/fagn)/#all galaxies(fagn = 0.1: active BH fraction)+ A lower fraction favors thedirect collapse scenario
as a primary process.
+ The current sample is biasedagainst heavily
W 1−W 2 colorobscuredof 0.48, just below the lowest color cut discussed Figure 12. Color–color diagram showing the locations of interesting classes ofthis work. The discovery of AGN activity in bulgeless and objects. Stars and early-type galaxies have colors near zero, while brown dwarfs
systems. inlow-massgalaxies is therefore not unprecedented. Furthermore, are very red in W1–W2, spiral galaxies are red in W2–W3, and ULIRGS tend to
be red in both colors.
Satyapal et al.

#AGN/#all galaxies

The Astrophysical Journal, 784:113 (8pp), 2014 April 1

there are 57 optically identified AGNs in our bulgeless sample,
16 of which also have W 1 − W 2 greater than 0.5, suggestingthat the AGN dominates over the host galaxy emission in these
4.1. Brown Dwarf Stars
16 galaxies. In AGN-dominated galaxies, the W 2 luminosity is
expected to originate almost entirely from the AGN (Stern et al. Brown dwarf stars are very faint, since they are not massive2012). In the 16 optical AGNs that also have red WISE colors, enough to fuse hydrogen into helium. As a result, they gradually
will be very cool andthe W 2 luminosities range from log(LW 2 (erg s−1 )) = 42.3 to fade and cool, and old brown dwarfs−9agnfaint.
BothJupiterwithL=10L⊙ and Gliese 229B with
44.6, with a mean of 43.7. By comparison, the W 2 luminosi−5ties of our full sample of 337 optically normal galaxies with L = 10 L⊙ have very strong emission at 4.6 µm due toW 1 − W 2 ! 0.5 range from log(LW 2 (erg s−1 )) = 41.6 to 45.0, a lack of methane absorption at this wavelength (Kirkpatrickwith a mean of 43.8 (erg s−1 ). Thus, even if a putative AGN in 2005). Thus, the 4.6 µm band of WISE is a powerful tool forthese galaxies dominates over its host, the implied total AGN finding cool brown dwarfs. Most of the brown dwarfs found prior
to WISE have been discovered using the z′ band of SDSS orluminosity is by no means extreme.
Based on all available data and the published work on WISE the J band of 2MASS or UKIDSS, but fairly high temperaturescolors of galaxies thus far, the red mid-infrared colors of the are required before there is substantial emission in either of thesebulgeless galaxies presented in this work are difficult to explain short-wavelength bands. As a result the currently known
galsamplesun
without invoking the presence of obscured AGNs. Follow-up of brownbiasedtowardthe byhotter,thusofyounger,Figuredwarfs
5. Fractionisof AGN
candidates
identified
WISE asanda function
stellar+ MIR diagnostics studies suggest
high AGN fractions of > 10%, thus
the occupation fraction > 100%!?
+ Hard X-ray observations arecrucial for drawing a robust
conclusion.

(Satyapal+14)

f= 10%log (M /M)Green Pea galaxies+ Green Pea galaxies were identified in an SDSS catalog, and theirappearances are interpreted as strong [O III] emission w/ high EWs.
(Cardamone+09).
+ They are low stellar-mass and metallicity species, and regarded
as those resemble to galaxies in an early phase of the galaxy formation.
log M★/Msun~ 9.5

SDSS J0749+3337

log M★/Msun~ 8.4

SDSS J0822+2241

y = 0.96 x - 8.37

AGN-like MIR properties
y = 1.00 x - 8.80

+ The two GPs are consistent with having AGNs in the MIR band.
- MIR luminosities are higher than expected from the SFRs
→ A further energy source, or AGN?
- Red colors
NuSTARand XMM-Newton
Study
GPs& Ko774:62 (10pp),
2013 A
September
Lee,ofHwang,→ Hotterdust1 emission
from theAGN
torus?

3 &K
Lee, Hwang,

2

Jarrett+13-1

log(sSFR/Gyr )[3.4] - [4.6] (Vega)

log SFRHα (M yr-1)

2ancy could
be explained if a mass ac3
le is deeplyThisstudy(non-linear)
1.039.02the surroundingy = 0.96
y =buried
0.96
x -in
8.37
1.8
1.8 x - 8.37
studyline(linear)
erefore theThis
narrow
regionremains
J0822+22
8.78
y = 1.00 x - 8.80
y = 1.00 x - 8.80
1.6
manishi2 et Jarrett+13
al. 2001, 2006, 2008, 2010;
1.4
Ichikawa Shi+12
et al. 2014). To provide new
1.4
discussion, we present the first hard X1.2
1IRal.luminous
d with 1NuSTAR (Harrison et2013),
J0749+33
1st sensitive hard X-ray (3–80 keV) ob0.6
ionally, soft X-ray properties are exam0.80
M-Newton (Jansen et al. 2001) archival
Jarrett+110.6
0.2
TAR and XMM-Newton observations
Stern+12Our GPs
in 2018
0.4
NLS1-GPs-1 (PI: Kawamuro) and in 2013-0.2 Star-forming GPs
ctively, and the log of these X-ray ob0.2
n in Table 2.
1.5
2
2.5
3
3.5
4
4.5
5-2 paper is organized as follows.
r of this[4.6] - [12.0] (Vega)
117 the8MIR
9properties
10 of 11y summarize
Thisstudy(non-linear)
This studyFigure
1. (non-linear)
MIR 4.6–12.0 µm versus 3.4–4.6 µm colorLW4WISE(L ) data
J0822+2241
ontheThisbased
study log(linear)
This study (linear)color plot. Black dashed and dot-dashed lines represent theJarrett+13

Settling time (typical)

200 s

X-ray observatories
Sensitivity(10 s, 3σ, ΔE/E = 0.5)

*NuSTAR is designed to be able to6

Background in HPD
6-10 keV
2 x 10-15 erg cm-2 s-1
10 – 30 keV+ Currently, XMM-Newton (< 10 keV) andNuSTAR(>10 keV) provide-14-2 -1
10-30 keV
1 x 10 erg cm s
30 – 60 keV

high-quality broadband X-ray spectra.

+ We obtained and analyzed NuSTAR and XMM-Newton data for the GPs.
XMM-Newton

NuChSTAR

radankuzaSu

SwiftFigure 5
comparedtelescopes
these sof
focusing c(NuSTAR observatory guide)Soft X-ray emission from XMM-Newtonet al.
+ Significant soft X-ray Kawamuro
emission 6wasdetected in both the GPs.
+ X-ray luminosities of ~1042 erg s-1 are comparable to those of
low-luminosity AGNs.

9 1020-1

counts s-1 keV-1

3040

NuSTAR/FPMA+FPMB-1-1 -1XMM-Newton/PN

9 1020304050

NuSTAR/FPMA+FPMB

src region
bk region
3-310-2

1045J0822+2241

6789 1020304050304050

NuSTAR/FPMA+FPMB
XMM-Newton/PN

10-410-3
10-510-4
10-63-2

src region
bk region
src region
45bk region

SNR (0.4-7 keV) ~ 66789 102010-1

XMM-Newton/MOS1+MOS2
XMM-Newton/PN
10-3-1

XMM-Newton/MOS1+MOS2
XMM-Newton/PN

counts s-1 keV-1

80.6 0.7 0.80.9 1234567 8 9

XMM-Newton/MOS1+MOS2
Energy (keV)

10-4

10-2

eV-1

710-5
10-6

50-1

810-4

countss -1keVcountss-1 keV

7-3-1

Kawamuro etal.J0822+2241
J0749+3337
10NuSTAR/FPMA+FPMB

Kawamu10-3

SNR (0.4-7 keV) ~ 7

src region
bk region
0.2

0.3

0.4

0.5 0.6 0.7 0.80.9 1234567 8 9

XMM-Newton/MOS1+MOS2
Energy (keV)Soft X-ray emission from XMM-Newton+ Significant soft X-ray emission was detected in both the GPs.
+ X-ray luminosities of ~1042 erg s-1 are comparable to those of
low-luminosity AGNs.
+ However, it may be ascribed to emission from the SF.
- low metallicity and young galaxies may have enhanced soft
X-ray emission from HMXBs.
- Because of low metal, ineﬃcient outflow leads to the massive XRBs,
orTheX-rayluminous
populations(e.g., Fragos+13)
AstrophysicalJournal, 764:41 (13pp),
2013 February 10
Fragos et al.
(Fragos+13)2.4. Parameter Study

Lx-SFR-Z empirical relation
StarTrack PS models have a significant number of freeparameters that can be categorized into two groups. In the(Brorby+16)
first group there are parameters that usually correspond to thedistributions of the initial properties of the binary population,such as the initial mass function (IMF), the initial binary mass
ratio (q), and the distribution of initial orbital separations.
For these parameters, we primarily use fixed values derived fromthe most updated observational surveys. Only in the case where
there is an ongoing debate regarding a parameter we actuallytreat it as a free parameter. In the same group one should add
parameters such as the stellar wind prescriptions and the natal
kick distribution of NSs, as these parameters are also derived
from observational data. The second group is that of the few“true” free parameters that correspond to poorly understoodphysical processes which we are not able to model in detail. In
this second group belong parameters such as those involved in
the CE phase modeling.
We created the largest ever grid of 288 PS models. Eachof these 288 models was run at nine different values ofmetallicity (Z = 10−4 –0.03), where we followed the evolutionof ∼45 million binaries per model. The whole set of simulations

Insignificant hard (> 10 keV) emission

counts s-1 keV-1+ Even the most sensitive hard X-ray observatory of NuSTAR cannot
detect X-rays, direct evidence for the presence of an AGN
NuSTAR/FPMA+FPMB

Kawamuro et al.
10-4
10-5
10-6

src region
bk region
34

SNR (3-50 keV) ~ 1.2
5678

9 102030

40

50

40

50

10-2

40

10-3

50

J0822+2241

NuSTAR/FPMA+FPMB
XMM-Newton/PN

10-3
10-4-510-4-610-2
103eV-1

30-1-1countscountsss-1keVkeV-1

FPMA+FPMB

0J0749+3337

10-3

10-2

src
src region
regionbkregionbk region
4SNR (3-50 keV) ~ 0.75678

9 102030

Energy (keV) XMM-Newton/MOS1+MOS2

Insignificant hard (> 10 keV) emission

counts s-1 keV-1+ Even the most sensitive hard X-ray observatory of NuSTAR cannot
detect X-rays, direct evidence for the presence of an AGN
NuSTAR/FPMA+FPMB

Kawamuro et al.
10-4
10-5
10-6

src region
bk region
34

SNR (3-50 keV) ~ 1.2
56789 102030

4050

10-2-3
NuSTAR/FPMA+FPMB
J0822+2241
XMM-Newton/PN have(1) No AGN exist, 10thus
suggesting that low stellar-mass
10-3 properties.
AGN-like MIR
10-4
However, …
-5(2) Heavily obscured
AGNs w/ NH > 2e+24 may be present,
10-4
src
src region
region SNR (3-50 keV) ~ 0.7
but cannot be detectedeven in the hard X-ray band.
bkregionbk region

40-6
10-2
10350eV-1

30-1-1countscountsss-1keV
keV-1FPMA+FPMB

0J0749+3337

10-3

10-2456789 10203040

Energy (keV) XMM-Newton/MOS1+MOS250

Summary+ The BH fraction is a clue to distinguish b/w the BH seedscenarios. → Need to built an unbiased AGN sample.
+ IR and optical data of representative low stellar-mass GPs
are controversial for the presence of an AGN.
→ X-ray observations !
+ We analyzed the first broadband X-ray data of two GPs
by using XMM-Newton and NuSTAR.
- Soft X-ray emission was found but may be ascribed to SF.
- Hard X-ray emission was not found.
+ Indeed, two possibilities still remain unfortunately…
(1) No AGN exist, thus suggesting that low stellar-mass have
AGN-like properties.
We may need to care about this fact in studying such objects.
(2) Heavily obscured AGNs are present, but cannot be
detected even in the hard X-ray band.