J/ApJ/819/162 Chandra obs. of ultracompact dwarf galaxies (UCDs) (Pandya+, 2016)
A comprehensive archival Chandra search for X-ray emission from
ultracompact dwarf galaxies.
Pandya V., Mulchaey J., Greene J.E.
<Astrophys. J., 819, 162 (2016)>
=2016ApJ...819..162P 2016ApJ...819..162P (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, optical ; Radial velocities ; X-ray sources
Keywords: accretion, accretion disks; galaxies: active; galaxies: dwarf;
quasars: supermassive black holes; X-rays: binaries; X-rays: galaxies
Abstract:
We present the first comprehensive archival study of the X-ray
properties of ultracompact dwarf (UCD) galaxies, with the goal of
identifying weakly accreting central black holes in UCDs. Our study
spans 578 UCDs distributed across 13 different host systems, including
clusters, groups, fossil groups, and isolated galaxies. Of the 336
spectroscopically confirmed UCDs with usable archival Chandra imaging
observations, 21 are X-ray-detected. Imposing a completeness limit of
LX>2x1038erg/s, the global X-ray detection fraction for the UCD
population is ∼3%. Of the 21 X-ray-detected UCDs, seven show evidence
of long-term X-ray time variability on the order of months to years.
X-ray-detected UCDs tend to be more compact than non-X-ray-detected
UCDs, and we find tentative evidence that the X-ray detection fraction
increases with surface luminosity density and global stellar velocity
dispersion. The X-ray emission of UCDs is fully consistent with
arising from a population of low-mass X-ray binaries (LMXBs). In fact,
there are fewer X-ray sources than expected using a naive
extrapolation from globular clusters. Invoking the fundamental plane
of black hole activity for SUCD1 near the Sombrero galaxy, for which
archival Jansky Very Large Array imaging at 5GHz is publicly
available, we set an upper limit on the mass of a hypothetical central
black hole in that UCD to be ≲105M☉. While the majority of
our sources are likely LMXBs, we cannot rule out central black holes
in some UCDs based on X-rays alone, and so we address the utility of
follow-up radio observations to find weakly accreting central black
holes.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 121 21 Optical properties of X-ray-detected ultracompact
dwarf (UCD) galaxies
table4.dat 207 21 X-ray properties of X-ray-detected UCDs
table6.dat 157 402 Optical and X-ray properties of
non-X-ray-detected UCDs
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-2014)
IX/45 : The Chandra Source Catalog, Release 1.1 (Evans+ 2012)
J/A+A/586/A102 : UCDs in the halo of NGC1399 (Voggel+, 2016)
J/ApJ/802/30 : NGVS VI. Ultra-compact dwarfs in M87 (Zhang+, 2015)
J/MNRAS/443/1151 : AIMSS Project. I. Compact Stellar Systems (Norris+, 2014)
J/AJ/148/32 : Globular cluster candidates in NGC 3115 (Jennings+, 2014)
J/ApJS/204/14 : Deep Chandra observations of NGC 4649. I. (Luo+, 2013)
J/MNRAS/422/885 : Ultracompact dwarf galaxies in Perseus (Penny+, 2012)
J/ApJ/748/124 : AGN X-ray variability in the 4Ms catalog (Young+, 2012)
J/AJ/142/199 : Sizes and luminosities of stellar systems (Brodie+, 2011)
J/ApJ/737/86 : UCD galaxies in the Coma cluster (Chiboucas+, 2011)
J/MNRAS/414/3699 : Study of hot stellar systems and galaxies (Misgeld+, 2011)
J/A+A/531/A4 : Ultra compact dwarfs and globulars in Hya I (Misgeld+, 2011)
J/ApJ/714/25 : AMUSE-Virgo survey. II. (Gallo+, 2010)
J/AJ/137/498 : UCD and bright GC in Fornax (Gregg+, 2009)
J/A+A/486/697 : Hydra I Cluster Catalogue (HCC) (Misgeld+, 2008)
J/A+A/472/111 : Centaurus Compact Object Survey (Mieske+, 2007)
J/A+A/464/L21 : Velocities of globular clusters in Fornax (Bergond+, 2007)
J/A+A/418/445 : FCOS Ultra Compact Dwarf galaxies RVs (Mieske+, 2004)
J/ApJ/613/279 : ACS Virgo Cluster Survey. III. M87 (Jordan+, 2004)
J/ApJS/150/367 : Globular clusters in NGC 5128 (Peng+, 2004)
J/ApJS/79/77 : Bell Lab. H I Survey - High Velocity Clouds (Stark+ 1992)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- UCD Adopted UCD literature name
17 A1 --- f_UCD Flag on UCD (G1)
20- 27 A8 --- Syst UCD host system
29- 37 F9.5 deg RAdeg Right Ascension of the optical source (J2000)
39- 47 F9.5 deg DEdeg Declination of the optical source (J2000)
49- 53 F5.2 Mpc Dist [3/21] Adopted distance
55- 59 F5.2 mag VMag [9.8/14.2]? Absolute V band magnitude
61- 64 F4.2 [Msun] logM [6/9]? Log dynamical mass
66- 68 F3.1 [Msun] e_logM [5/8]? Uncertainty in logM
70- 74 F5.2 pc rhl [1.8/24.2]? Optical half-light radius
76- 78 F3.1 pc e_rhl [0.5/1.4]? Uncertainty in rhl
80- 85 F6.1 km/s HRV [440/2024] Heliocentric radial velocity
87- 90 F4.1 km/s sigma [8/68]? Global stellar velocity dispersion
92- 94 F3.1 km/s e_sigma [1/6]? Uncertainty in sigma
96- 98 F3.1 [Msun/Lsun] M/L [0.9/5]? Dynamical mass-to-light ratio
in the V-band
100-102 F3.1 [Msun/Lsun] e_M/L [0.3/1.4]? Uncertainty in M/L
104-109 F6.3 --- nLMXB [0.01/14]? Expected number of LMXBs (1)
111-121 A11 --- Ref Primary reference for UCD's
optical properties (2)
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Note (1): According to equation 17 of Sivakoff et al. (2007ApJ...660.1246S 2007ApJ...660.1246S).
Note (2): Reference as follows:
Mieske+13 = 2013A&A...558A..14M 2013A&A...558A..14M
Mieske+08a = 2008A&A...489.1023M 2008A&A...489.1023M
Gregg+09 = 2009, J/AJ/137/498
Rijkuba+07 = 2007A&A...469..147R 2007A&A...469..147R
Hau+09 = 2009MNRAS.394L..97H 2009MNRAS.394L..97H
Strader+13 = 2013ApJ...775L...6S 2013ApJ...775L...6S
Sandoval+15 = 2015ApJ...808L..32S 2015ApJ...808L..32S
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- UCD Adopted UCD literature name
17 A1 --- f_UCD Flag on UCD (G1)
18 A1 --- n_UCD Note on UCD (3)
20- 27 A8 --- Syst UCD host system
29- 31 I3 ks Exp [39/843] Total exposure time
33- 35 F3.1 arcmin theta Average off-axis angle (4)
37- 40 F4.2 arcsec sx [0.1/1.5]? Separation between optical
X-ray positions (5)
42- 45 F4.1 arcsec Rad [1.9/17] Average radius of circular aperture (6)
47- 53 F7.2 ct NCF [5/3587] Net full band (0.5-7 keV) counts
55- 59 F5.2 ct e_NCF The 1σ uncertainty in NCF (7)
61- 67 F7.2 ct NCH [0.5/1313] Net hard band (2-7 keV) counts
69- 73 F5.2 ct e_NCH The 1σ uncertainty in NCH (7)
75- 81 F7.2 ct NCS [4/2287] Net soft band (0.5-2 keV) counts
83- 87 F5.2 ct e_NCS The 1σ uncertainty in NCS (7)
89- 94 F6.2 [mW/m2] logFF [-15.4/-13.1] Log Full band (0.5-7 keV) flux;
in erg/s/cm2
96- 99 F4.2 [mW/m2] E_logFF Upper 90% confidence interval in FF
101-104 F4.2 [mW/m2] e_logFF Lower 90% confidence interval in FF
106-111 F6.2 [mW/m2] logFH [-14.8/-13.3] Log Hard band (2-7 keV) flux;
in erg/s/cm2
113-116 F4.2 [mW/m2] E_logFH Upper 90% confidence interval in FH
118-121 F4.2 [mW/m2] e_logFH Lower 90% confidence interval in FH
123-128 F6.2 [mW/m2] logFS [-15.8/-13.6] Log Soft band (0.5-2 keV) flux;
in erg/s/cm2
130-133 F4.2 [mW/m2] E_logFS Upper 90% confidence interval in FS
135-138 F4.2 [mW/m2] e_logFS Lower 90% confidence interval in FS
140-144 F5.2 [10-7W] logLF [36.4/38.8] Log Full band (0.5-7keV) luminosity;
in erg/s
146-149 F4.2 [10-7W] E_logLF Upper 90% confidence interval in LF
151-154 F4.2 [10-7W] e_logLF Lower 90% confidence interval in LF
156-160 F5.2 [10-7W] logLH [36.4/38.7] Log Hard band (2-7 keV) luminosity;
in erg/s
162-165 F4.2 [10-7W] E_logLH Upper 90% confidence interval in LH
167-170 F4.2 [10-7W] e_logLH Lower 90% confidence interval in LH
172-176 F5.2 [10-7W] logLS [36/38.3] Log Soft band (0.5-2 keV) luminosity;
in erg/s
178-181 F4.2 [10-7W] E_logLS Upper 90% confidence interval in LS
183-186 F4.2 [10-7W] e_logLS Lower 90% confidence interval in LS
188-192 F5.2 --- HR Classical hardness ratio ((CH-CS)/(CH+CS))
194-197 F4.2 --- gamma [0.9/1.8] Best-fit power law photon index (8)
199-202 F4.2 --- E_gamma ? Upper 90% confidence interval in gamma
204-207 F4.2 --- e_gamma ? Lower 90% confidence interval in gamma
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Note (3):
d = a borderline detection (net counts are consistent with zero); see
Appendix B for more information.
Note (4): Exposure time-weighted. Of all observations used for flux derivation.
Note (5): Between the optical position of the UCD and the center of the
cross-matched X-ray source's aperture as defined by wavdetect.
Note (6): Exposure time-weighted. Used to enclose 90% of the PSF
in the individual observations.
Note (7): Gehrels (1986ApJ...303..336G 1986ApJ...303..336G).
Note (8): Set to 1.49, the median of the 11 derived indices, if gamma was
fixed due to NCF<100.
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 20 A20 --- UCD Adopted UCD literature name (1)
22- 30 A9 --- Syst UCD host system
32- 40 F9.5 deg RAdeg Right Ascension in decimal degrees (J2000)
42- 50 F9.5 deg DEdeg Declination in decimal degrees (J2000)
52- 57 F6.2 Mpc Dist [3/105] Host system adopted distance
59- 64 F6.2 mag VMag [-16.2/-9.1]? Absolute V band magnitude
66- 69 F4.2 [Msun] logM [5/9]? Log dynamical mass
71- 76 F6.2 pc rhl [2.6/101]? Optical half-light radius
78- 83 F6.1 km/s HRV [300/9955]? Heliocentric radial velocity
85- 88 F4.1 km/s sigma [4/78]? Global stellar velocity dispersion
90- 94 F5.2 [Msun/Lsun] M/L [0.1/20]? Dynamical mass-to-light ratio
in the V-band
96- 99 I4 ks Exp [4/1494]? Total Chandra exposure time
101-104 F4.1 arcmin theta ? Average off-axis angle (2)
106-109 F4.1 arcsec Rad [0/26.2]? Average radius of circular
aperture (3)
111-117 F7.1 ct Cts [0/28921]? Total counts in source region
119-125 F7.1 ct Bkgd ? Scaled background counts in
background region
127-131 F5.1 --- U [0.9/393]? Number of counts expected (4)
133 A1 --- l_logFF Limit flag on logFF
134-138 F5.1 [mW/m2] logFF [-16/-13]? Log Full band (0.5-7 keV) flux
upper limit (based on U counts)
140 A1 --- l_logLF Limit flag on LF
141-144 F4.1 [10-7W] logLF [35/41]? Log Full band (0.5-7keV)
luminosity upper limit (based on U counts)
146-157 A12 --- Ref Primary reference for UCD's
optical properties (5)
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Note (1): Upper limits were derived only for spectroscopically-confirmed UCDs,
with the exception of NGC 3115 (which has ∼1.1Msec of imaging) and
NGC 1023 (which has no spectroscopically-confirmed UCDs). The UCDs
are sorted by right ascension and declination so that all UCDs from
the same host system are found in the same part of this table.
Note (2): Exposure time-weighted. Of all observations used for upper derivation.
Note (3): Exposure time-weighted. Used to enclose 90% of the PSF in
the individual observations.
Note (4): From a fluctuation in the local background with
Poisson probability 1%.
Note (5): Reference as follows:
Bergond+07 = 2007, J/A+A/464/L21 (<[BAL2007] ucNNN.NN> in Simbad)
Chiboucas+11 = 2011, J/ApJ/737/86 (<[CTM2010] NNNNNNN> in Simbad)
DaRocha+11 = 2011A&A...525A..86D 2011A&A...525A..86D (<[DMG2011] HCG90 UCDN> in Simbad)
Firth+08 = 2008MNRAS.389.1539F 2008MNRAS.389.1539F (<[FDK2008] JHHMMSS.ss+DDMMSS.s> in Simbad)
Francis+12 = 2012MNRAS.425..325F 2012MNRAS.425..325F
Gregg+09 = 2009, J/AJ/137/498 (<[GDE2009] UCD NN> in Simbad)
Hasegan+05 = 2005ApJ...627..203H 2005ApJ...627..203H
Hilker+07 = 2007A&A...463..119H 2007A&A...463..119H
Jennings+14 = 2014, J/AJ/148/32 (<[JSR2014] UCDNNN> in Simbad)
Liu+15 = 2015ApJ...812L...2L 2015ApJ...812L...2L
Madrid+13 = 2013ApJ...770..158M 2013ApJ...770..158M (<[MD2013] UCDN> in Simbad)
Maraston+04 = 2004A&A...416..467M 2004A&A...416..467M
Mieske+07a = 2007, J/A+A/472/111 ( in Simbad)
Mieske+07b = 2007ggnu.conf..103M
Mieske+08 = 2008A&A...489.1023M 2008A&A...489.1023M
Mieske+09 = 2009A&A...498..705M 2009A&A...498..705M
Misgeld+08 = 2008, J/A+A/486/697 (<[MMH2008] Na-NN> or
<[MMH2008] aN-NN> in Simbad)
Misgeld+11 = 2011, J/A+A/531/A4 (<[MMH2011] HUCDNN> in Simbad)
Norris+14 = 2014, J/MNRAS/443/1151
Penny+12 = 2012, J/MNRAS/422/885 (<[PFC2012] UCD NN> in Simbad)
Rejkuba+07 = 2007A&A...469..147R 2007A&A...469..147R
Zhang+15 = 2015ApJ...802...30Z 2015ApJ...802...30Z
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Global note:
Note (G1):
* = X-ray emission from the UCD was detected during the second tier search
using individual rather than merged observations.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 27-May-2016