Gamma Rays From Nebulae
Associated with Microquasars
and Ultra-Luminous X-ray Sources
Yoshiyuki Inoue (ISAS/JAXA)
Shiu-Hang (Herman) Lee (ISAS -> Kyoto), Yasuyuki T. Tanaka(Hiroshima), Shogo B. Kobayashi (Tokyo)

CTA-Japan Meeting @ Kashiwa, 2016-12-15

Current View of VHE Gamma-Ray Sky©TeVCat• ~180 very high energy (VHE; >50 GeV) objects by imaging

atmospheric Cherenkov telescopes (IACTs; see TeVCat)• CTA will discover new cosmic-ray accelerators.

Microquasars and ULXs in Extragalactic Sky• Microquasars and ultra-luminous X-ray sources (ULXs) are• X-ray binary systems• Black hole mass is still under debate (intermediate orstellar)… or powered by pulsars (Bachetti+’14)• kinetic/radiative power >1039-40 erg/s (Mirabel &Rodriguez ’99, Feng & Soria ‘11)• associated with star-forming regions (e.g. Swartz+’09,

Poutanen+’13)

Notes.
a B and C configuration data were combined.
b 3σ upper limit.
c Unabsorbed flux in units of 10−12 erg cm−2 s−1 .

LETTERS

Micro-quasars and ULXs Bubbles

is a(2006),
Soria et al. (2006b), and Mezcua & Lobanov
IC342 X-1
.e.g.
ears.
X-ray spectra of ULXs share some similar properties with
nonicalblack hole states of Galactic black hole binaries
that
Bs;
ungKaaret & Feng 2009; Soria 2011). A number of ULXs
tate
& Kaaret 2006,
am- transitions (Kubota et al. 2001; Feng><
1
2
1
W.2010;
PakullServillat, Roberto
Soria& Christian Motch
Godet et al. 2009; Manfred
Grisé et al.
et al.
2011).
HBs during the X-ray hard state, the sources are associatedlf-absorbed compact jets (Corbel et al. 2004; Fender et al.
Given the similarities
between
ULXs
it Eddington
isof L0.3–10 < 1.8 3 1037 erg s21. Faint, even softer diffuse X-ray emission
Black-holeaccretionstatesandnearGBHBs,
or above theluminosity
at whichradiation
force outwards
ting
thepoint
presenceof suchcompact
jets for overcomes gravity) pervades much of the extent of the optical bubble. The morphology
me- to investigate(theare still poorly known because of the rarity of such sources.
strikingly resembles that of an FRII-type powerful active galaxy, diswith
hard
X-ray
spectra.
1
nt of
Ultraluminous X-ray sources are the most luminous class of black
playing X-ray and radio hot spots (for example Cygnus A11). The opticalhis
new radio and optical observations
rompaper, we present
hole (LX < 1040 erg s21) located outside the nuclei of active galaxies.
radial velocity of S26 agrees with that of other nearby nebulae in NGC
ULXs that are They
associatedlarge-scale
nebulae: rates, if they areare likely withto be accretingat super-Eddington
ghea
erg II X-1 (Ho powered
II X-1)byandNGC
In addition,
black
holes5408.
with masses
less than 100 solar masses.
adio
are often
associatedwith withshock-ionizedsent
a radionebulaassociatedIC 342 nebulae2,3, though−1 discovery of They
N
s ,
with
no
evidenceofcollimatedjets.
Microquasars
withsteadyjets
n Section 2,Figure
we describe
data1analysis,and3. Radioobservations,contours from Fig.
are overlaid
on an HST imageof 5 GHz image of IC 342 X-1 overlaid on the Hα HST image.
VLA
conare much less luminous. Here we report that the largeFigure
nebula1.S26
The energetics
ofal.theopticalandradio
and theKaaret etthatnearby
iscentredonnebulae
theHe7793II λ4686
line using
FR462N
represent radio emission and are drawn at 3, 4, 5, 6, 7, 8, 9, and(ref.(2004)
4) in thegalaxyNGC
is poweredby Contours
athe
black
hole
ased
perties of narrow-band
IC 342 with
X-1filter.
areinvestigatedin Section
3. toInthe famous
10 times
the rms noise level of 11 µJy beam−1 . The peak brightness is
a
pair
of
collimated
jets.
It
is
similar
Galactic
ofwe briefly summarize our results.
beam−1 . The resolution of the image is 2.′′ 3 × 1.′′ 6 at P.A. = −13◦nd 4,source SS433 (ref. 5), but twice as large and a few 122.4
times µJy
more

(Cseh et al. 2012)
Holmberg
II
X-1
(Cseh
et
al.
2014)
A 300-parsec-long jet-inflated bubble around a
Radio
+
HeII
4686
Radio
+
Hα
powerful microquasar in the galaxy NGC 7793

associate with expanding bubbles.

Downloaded from http://mnrasl.oxfordjournals• Some microquasars and ULXs

S26 (Pakull et al. 2010)
X-ray + Hα

Eyoung compact symmetric objects (CSOs; Wu et al. and2013),
and was made withretheaimage
Robust = 0 weighting. The sign “> <” marks thepowerful. We determine a mechanical power of around
few
X-ray
may diffuse
awaydecelerated
below
Machmorenumberof position
unity.
1040ANALYSIS,
erg
s21.once
The jets
therefore
seem
104atimes
energetic
than of the ULX.
.less
OBSERVATIONS,ANDRESULTS(A colorof this figure is available in the online journal.)
However,is yetemission
to be explained
mechanism
candriveofversion
antheitX-ray
from the whatcore. S26
has the structureareII (FRII-type)of IC 342
and Hoobject.
II active
X-1 galaxy: X-ray and opticalepisodicFanaroff–Riley
behaviouroftypeanX-1
accretings.1.ofVLA Observations
6
core, X-ray hot spots, radio lobes and an optical and X-ray cocoon.
GRS1915+105
is thought to be wobbling across the ‘jet line’
b
the
It is
a microquasar
most ofthe jet out
power is dissipated in
ervations of IC 342
X-1
and Ho II where
X-1 were
carried
−1
the
10σ
level
with
a
peak
intensity
of
∼120
µJy
beam
and
and
observed
toshowsuperluminal
ejectionsassociatedwith
Xthermalparticles
in
the
lobes
ratherthan
relativistic
electrons.
We
he C- and B-array configurations of the Very Large Array
estimatedtotal flux density in the nebula is ∼2 mJy. The
ray state transitions.
Thesestates and nebulaetransitions
couldthediffernot
TheAstronomy
very large,
shock-ionized(ultraluminous
X-ray
ndex
of the NationalRadio
Observatory(NRAO).
7
corresponding
luminosity at a distance of 3.9 Mpc (Tikhonov
source(ULX) bubbles), –withcharacteristic
sizes ofplateau,100–500
pc
just
from
the
canonical
onese.g.
hard state versus
stateservations were made
at
4.8
and
8.5
GHz
5 (VLA program
35
−1
and
ages
of
around
a
few
10
yr
are
much
largerandmoreenergetic&
Galazutdinova
2010)
is
L
=
1.8
×
10
erg
s
, withnebs(van
et al.
2010)– but alsoinfrom
the1.ones
Ho II X-1 has, ande theAL711)
andtheOers
detailsaresummarized
Table
Data
′′
′′
than normal supernova remnants. But X-ray luminous L
sourcesmay= νLν . We find that the size of the nebula is 16 × 8 , whichitisunclearhow
toreconcilesuchphenomenology
with
CSOs
and
tion,
thea (u,v) ofplane,
and imaging
weret al. combinationbeinonly
subsetnon-nuclear
black holes
at very highcorresponds
mass accre- to 300 pc × 150 pc. We estimate10thearcsecor 190 pcof thevolume8tion rates.
We proposed Image
that ionizedbubbles might also be foundout usingDDRGs.
the NRAO
Astronomical
Processing′′zing• R ~200 pc• v ~ 80-250 km/s

Expanding Power of Bubbles• Self-similar expansion law gives (Weaver+’77; Kaiser &Alexander ’97)

Rb ⇡ 0.76(Pkin /µmp ngas )1/5 3/5t• The characteristic age:1
⌧ = 3Rb /5vs ⇠ 4.9 ⇥ 10 Rb,20.8 vs,7.1 yr
4• The time-average kinetic power of the bubble:

2 3
40 2
3
1
Pkin ⇡ 18µmp ngas Rb vs ⇠ 3.6 ⇥ 10 Rb,20.8 vs,7.1 ngas,0.5 erg s1040 erg/s power is available.

Shock Condition

The Astrophysical Journal, 806:71 (12pp), 2015 June 10

Lee• Downstream temperature
5 2
Td ⇠ 2.0 ⇥ 10 vs,7.1 K• Radiative cooling time scale (Draine ‘11)
17/5
1
trad ⇠ 1.4 ⇥ 10 ngas,0.5 vs,7.1 yr
3➡Radiative shock

Lee+’15

Figure 1. (a) Spectra of re-accelerated Galactic CR at a steady cloud shock of velocities vsk < 120 km s−1. Here, the ambient magnetic ﬁeld B0 = 25 μG and T0
K in the shock precursor. The precursor ion fraction fion is estimated according to Hollenbach & McKee (1989) which changes the break momentum pbr ofaccelerated particles. The dashed lines show the ambient spectra of the CRs before re-acceleration. The upper thick and lower thin lines correspond to proto
electrons respectively. (b) Variation of escape-limited maximum momentum pmax , break momentum pbr and precursor ion fraction fion with shock velocity
correspondence with the spectra shown in panel (a).

• Ionized fraction strongly depends on the shock velocity(Shull & McKee ’79; Hollenbach & McKee ’89, Lee+’15)
the CR streaming instability in the shock precursor is inefﬁcientin the case of pure re-acceleration of Galactic CRs, so thatenergy loss of the re-accelerating electrons via synchrotron
radiation is slow in the immediate downstream region.
However, synchrotron losses can be much faster further
downstream when a highly compressed B-ﬁeld is present in
the radiatively cooled dense shell formed behind the cloudshock.
In this model, the precursor of a radiative shock withvsk ⩾ 120 km s−1 approaches full ionization by photoionization, and wave damping through ion-neutral collisions isineffective, so no break in the diffusion coefﬁcient and the CR

probably responsible for producing the bright radio synchr
ﬁlaments (Reach et al. 2005; Yoshiike et al. 2013).
The evolution of the shock hydrodynamics in the duniform medium is followed up to a time tc.8 Time snapsho
the proﬁles of hydrodynamic variables including total
density n, temperature T, magnetic ﬁeld strength B andvelocity v are shown in Figure 2 until the shock has just st
to become radiative. When the shock decelerates quickly
time in the dense medium and the post-shock gas temper
drops to around a few 105 K, radiative cooling bec
important. An enhancement of density and B-ﬁeld with
due to rapid compression can be observed. A cool dense• Ion-neutral collisions will hamper particle acc.
0.4 2
Ecr,br ⇠ 1.9 Tu,4 Bu, 6 (1fion )

1

1/2
3/2
fion ngas,0.5 GeV

Gamma-ray production• The maximum cosmic-ray energy
1/2
Ecr,max ⇠ 1.3 ⇥ 10 ⌘0 ngas,0.5 vs,7.1 Rb,20.8 TeV
21332

L. K. Hunt and H. Hirashita: The size-• ULXs are known to be associated withstar forming regions (Swartz+’09)• ngas ~ 1-10 cm-3 (Hunt & Hirashita ‘09)
• Hadronuclear interaction eﬃciency
1
fpp ⇠ 0.28Rb,20.8 vs,7.1 ngas,0.5
Hunt & Hirashita ‘09

Fig. 2. Densities ne vs. size (diameter) of the six H II-region samples
The extragalactic radio sample (except for M 33 and I Zw 18) is shownExpected Gamma-ray Spectra
10-10

S26 (ngas = 1 cm-3)
IC 342 X-1 (ngas = 1 cm-3)
IC 10 X-1 (ngas = 1 cm-3)
ngas = 3 cm-3
Fermi/LAT (10 years)
CTA-South (50 hr)

E2dN/dE (erg/cm2/s)

10-11

10-12

10

-13

10

-14

10-15 -2
10

10-1

100

101

102
103
Energy (GeV)

104

105

106

• Assuming 10% of kinetic energy goes into particle acc.
• Microquasar nebula S26 would be a good target for CTA

107

YI+’16

Emission in Galaxies
Ackermann et al.

SFR (M yr -1)

10-2
1043

1

• Host galaxy of S26 would

LAT Non-detected with AGN (Upper Limit)
LAT Detected
LAT Detected with AGN

41Best-fit
Fit Uncertainty
Dispersion

10

103

102

10

LAT Non-detected (Upper Limit)

4210

L0.1-100 GeV (erg s-1)

10-1

Arp 220

NGC 1068

Calorimetric Limit50(E η = 10 erg)

M82

SN

40

have comparable gammaray flux for ngas = 1 cm-3

NGC 2146

10

M83

1039

M31

NGC 4945
NGC 253
NGC 6946
IC 342Milky Way

M33

1038

• S26 is ~3’ away from the

LMC

1037

SMC

108

109
1010
1011
L8-1000 µm (L )Ackermann+’12-1

SFR (M yr )
10-2
10-1

10-1

1

L0.1-100 GeV / L8-1000 µm

10

102

10

103

NGC 7793

LAT Non-detected (Upper Limit)

LAT Non-detected with AGN (Upper Limit)
LAT Detected
LAT Detected with AGN

-2

1012

3’

Best-fit
Fit Uncertainty
Dispersion
Calorimetric Limit50(E η = 10 erg)

-3

SN

10

NGC 2146
Arp 220

10-4

M83
NGC 253
NGC 6946
IC 342

M33
SMC

8

10

NGC 1068

M31

LMC

10-5

NGC 4945
M82

Milky Way

9

10

L

10

10

11

10
(L )

©NASA
1012

nucleus
CTA Angular
Resolution

Cosmic Gamma-ray Background Radiation

Figure 4. Upper limits on
and U U  (bottom) channthe conservative and s
Ajello, YI, +’15 to(2014b). The blue bandsignal intensities due to th
Figure 3. Top panel: integrated emission of blazars (with and without EBL
our Galaxy as well as othe
absorption), compared to the intensity of the EGB (data points from AC14).
mass of 10 6M:. For co
Lowerpanel:
as, above,
butgalaxies
including also
the, emission
from galaxies
star-forming (Ackermann+’12)• Blazars (YI & Totani’09;
Ajello,YI+’15)Radio(YI’11)
Starburst
shown (Abramowski et algalaxies (gray band; Ackermann et al. 2012b) and radio galaxies (black striped
band; Inoue 2011) as well as the sum of all non-exotic components (yellowband).
An exampleof DM-inducedbackgroundγ-ray signal ruled out
by ourresolved
analysis is yet (Ackermann+’14).
• 60-70 % of thecosmicgamma-ray
is notshown by the solid pink line and summed with the non-exotic components(long-dashed pink line). The inset shows the residual emission, computed asTi, ASTRO /Fi, ASTRO §, it
the ratiocontributeof the summed contribution
toofthethe
EGBunresolved
spectrum, as a functionof• ULX bubbles would
to~7%
backgroundis the sum (inTi flux.
energy as well as the uncertainty due to the foreground emission models
unresolved EGB and(see AC14).

foreground (AC14).

Neutrino Production?
10-10

E2dN/dE (erg/cm2/s)

10-11

10-12

10

-13

10

-14

10

-15

102

S26 (ngas = 1 cm-3)-3
ngas = 3 cm
IceCube (Northern Sky)
IceCube (Southern Sky)
103

104

105
Energy (GeV)

106

107

108

YI+’16• A factor of ~10 sensitive neutrino detectors will be able to see the object.
• But, contamination of host galaxies would be significant.

Summary• Microquasar/ULX bubbles are eﬃcient cosmic-ray

accelerators.
• Especially, the bubbles of S26 will a good target for future

CTA observations.
• Host galaxy contamination can be removed by CTA’s

angular resolution.
• These bubbles would make up ~7% of the unresolved

gamma-ray background.
• ULX workshop @ ISAS, 2017/3/6-7

s1
s2

2.35±0.07+0.2
2.80.1+0.8
1.40.4+0.2
1.6-0.3+0.3
2.10.2+0.07
1.250.06+0.07
0.220.05
0.7±0.2

L
L
+1
75
+6
12-5

0.49±0.07
0.66±0.03
<26.4
+10
4.63.5L
L+0.9
2.90.61.7±0.2

1.27/131
1.19/143
1.23/1291.21/141

40.3
40.6
40.2
40.4

Evidence of ULX Jets?

s indicating the 1σ conﬁdence regions. Columns: (1) X-ray model, as described in Section 3.1. (2) Intrinsic hydrogen column density. (3) Inner
Photon index for the DISKIR model and the optical depth of the Comptonizing component for the MCD+CompTT model. (5) Inner disk radius
For the DISKIR and MCD+COMPTT models these were calculated using the normalization. For the SIRF model they were estimated using the(see Abolmasov et al. 2009) and the luminosity. See Section 3.1 for more details. (6) Electron temperature. (7) Reduced χ2 values for the ﬁt ands of freedom. (8) Unabsorbed (intrinsic) luminosities between 0.3 and 10 keV.

• ULX jets are notestablished yet.
• Possible synchrotron

self-absorption (SSA)feature is discovered for
Hol IX X-1 (Dudik+’16).
Dudik+’16

tructed in Section 3. The HST data are taken from Grisé et al. (2011), the XMM OM UV data from Berghea & Dudik (2012). The twodata sets (XMM-Newton data sets 0112521101 and 0693851701 shown as obs 1 in blue and obs 2 in green, respectively) are taken from Luangtip
ars are 1σ.

note that some fraction of the IR emission
from contamination from the bubble nebula.
1) found some red excess in the I band basedodel ﬁts to the HST data. However, the HST
study suggest that the I-band emission is not• or, circumbinary disk?

∼400 K from the Galactic X-ray binary GRS 1915+105. GRS
1915+105 is a microquasar that has a red giant as a donor(Greiner et al. 2001). Rahoui et al. (2010) suggest that the dust
component could be related to the dusty shell often foundsurrounding red giants. We ﬁt a spherical blackbody model toMWL Spectrum of Hol IX X-1 from Jet• Assuming SSA, B ~ 3.4 x
10

Hol IX X-1
Syn
SSC
EIC (r = 3 Rb)
EIC (r = 10 Rb)

10-12

E2dN/dE (erg/cm2/s)

104 G & Rb ~ 1.6 x 109 cm-11• Similar to Galactic X-ray

binaries (e.g. Tanaka, YI+’16 for

10-13

V404 Cyg)
10-14• location r > 2 Rb
10-15

10-2

10-1

100

101

102 103 104
Energy (eV)

105

106

107

108

• ~1000 rs for 10 Msun
• 10 rs for 1000 Msun

2103

1

2

5
10
39
Luminosity/10 (erg/s)

20

10
dN/dL

0.1

dN/dL

1
0.1

20

50

Swartz+’11

Figure 4. Cumulative X-ray luminosity functions of galaxies from the pri- 40 Figure 6. Cumulative (upper panels) and differential (lower panels) ULX luminosity functmary sample, normalized by their respective SFRs. The solid line is theand luminosities estimated from the detected number of counts (right panels). Two mode
−α1
−α1cumulative XLF per unit SFR, given by integration of equation (18).

• A simple power-law (γ~1.6) + cutoﬀ (10asum of the SFR of all galaxies contributing to the given luminosity
bins. The latter step is required to account for the fact that different
galaxies
have different point-source detection sensitivity. However,•
because of the considerable dispersion in the normalization (Fig. 4),
the luminosity function thus computed may have a number of artificial• steps and features at the luminosities corresponding to theluminosity limits of particular galaxies. In order to deal with thisf5
10
Luminosity/1039 (erg/s)

ULX LF in the local Universe

Downloaded from http://mnras.oxfordjournals.org/ at U

Mineo+’12

h
-

)

2

10

XRB LF in each galaxy

1

1

HMXBs in star-forming galaxies

1

1

ULX Luminosity Function

erg/s)

CLX exp(−LX /Lc ), and a pure power-law model, CLX . See Table 2 for model fit parame(A color versionSwartz+’11,Walton+’11,Mineo+’12).
of this figure is available in the online journal.)
intologarithmicallyspaced arebins andnormalize the result
by the• e.g.
Variousstudiesconsistent(e.g.
Grimm+’03,

3
−2.0
Th
(Table
2),
dN/dL
=
1.79
±
0.48SFRL
where
L
is
in
cts
cts Mpc .
Swartz+’11 provides a ULX LF from a complete39sample
inthevolumects of 6100
galax
units of 10 erg s−1 . Scaling Equation (6) of Grimm et al.
funct(2003) to the same luminosity normalization and accounting for
By setting Eddington ratio, we can convert
ULX LF
to ULX
function.
2004
thebandpass,
2–10BH
keV,massover which
they estimated
15 narrower−1.6

" = 1.7 and the Galactic line-of-sight hydrogen column density
NH = 3.4 × 1020 cm−2 (Stark et al. 1992). These luminosities wererecomputed for the distance to the Antennae galaxies of 22 Mpc asrecommended by Schweizer et al. (2008). This distance gives thescale of 107 pc arcsec−1 and the distance modulus −31.71.

.oxfordjournals.org/ at Uchu Kagaku Kenkyujo on March 1, 2016

Schweizer 1995). Zezas et al. (2002b) have noticed
the brightest X-ray sources are displaced from thestar clusters. However, their absolute astrometry has
c error (∼160 pc); therefore, they could not possibly
acements smaller than that and prove unambiguously

ULX Lifetime• Binary models predict X-ray activity

time scale tULX~0.1 Myr for high mass
X-ray binary systems (Mineo+’12).
• ULXs are known to be associatedwith stellar clusters (Grisé+’11, Poutanen+’13)• the age of those clusters are <~5

Poutanen+’13512

Myr (Grisé+’11, Poutanen+’13)

J. Poutanen et al.

The Astrophysical Journal, 734:23 (14pp), 2011 June 10(Leitherer et al. 1999; Vázquez & Leitherer 2005). We consider the

rgb image of Antennae produced from HST/ACS images taken in FR656N (Hα, red), F435W (blue) and F550M(green) bands. NE
bar length
instantaneous
starburst
model with the Kroupa (2001) initial mass
5 arcsec (107 pc/1 arcsec). The VIMOS frames of the studied ULX regions together with Chandra positions (1.0 arcsec radius) are indicated infunction (IMF) extending to 150 M⊙ for solar and double-solar
ce numbers correspond to the catalogue of Zezas et al. (2002a). The VIMOS continuum images have been extracted in the ACS band F550M
metallicities (see Fig. 7). The cluster next to X-11 is consistentpositions are shown by black circles of 0.3 arcsec in radius.

Downloaded from

Poutanen+’13

with the solar metallicity and those next to X-32, 35 and X-44 with
only double-solar metallicity. On the other hand, the colours of theclusters next to X-16, 31 and 42 can be described by any metallicity
from solar to double solar, which is consistent with the range ofmetallicities from 0.9 to 1.3 Z⊙ found by Bastian et al. (2009) intheir study of 16 young clusters in the Antennae. For the cluster nextto X-44, we took the Galactic extinction and increasing the valueof AV would shift the cluster even further away from the theoreticaltracks to the lower-left corner of the colour–colour diagram.
The overlap at the colour–colour diagram between the cluster
error contours and the evolutionary tracks gives us an estimate of
the cluster ages. We find that all clusters associated with the ULXs
are extremely young with the age of less than 6 Myr (see Table 3).4
For the assumed metallicity, an improved estimate for AV can beobtained from the same overlap. Comparing thus obtained MV tothe theoretical absolute magnitude from the STARBURST99 models
16of mass 106 M⊙ ), we find the cluster masses using(for a cluster
equation #MV = −2.5 log (Mclus /106 M ) (see Table 3), which

Grisé+’11

BBH merger rate [Gpc-3 yr-1]

Binary BH Merger Rates inferred from ULXs
102

• We can estimate theaLIGO event rate range

101

expected merger rate, if allbinary black holes evolves
through X-ray emitting
phases.

100
10-1
10

-2

10-3

ULX LF (tULX = 0.1 Myr)
σλ=1
σλ=3
(tULX,c, σt) = (0.1 Myr, 1)(tULX,c, σt) = (1 Myr, 1)

0.1

1• The expected rate is10

Eddington ratio λYI, Tanaka, & Isobe ‘16

coincident with themeasured merger rate.

dn fHMXB fratio⇢(M
˙ BH ; ) ⇡ MBH
dMBH
tULX
✓
◆ 0.6
◆✓
◆ 1✓
◆✓
◆
✓
MBH
fHMXB
fratio
MBH
tULX
3
1
' 50
[Gpc
yr
]
exp
2
M
1.2 ⇥ 10 M
0.1 Myr
0.6
0.2
17