J/ApJ/929/84 Xray obs. of gal. hosting nuclear star clusters (Baldassare+, 2022)
Massive black hole formation in dense stellar environments: enhanced X-ray
detection rates in high-velocity dispersion nuclear star clusters.
Baldassare V.F., Stone N.C., Foord A., Gallo E., Ostriker J.P.
<Astrophys. J., 929, 84 (2022)>
=2022ApJ...929...84B 2022ApJ...929...84B
ADC_Keywords: Active gal. nuclei; X-ray sources; Velocity dispersion
Keywords: Nucleated dwarf galaxies ; Intermediate-mass black holes ;
Astrophysical black holes ; Low-luminosity active galactic nuclei
Abstract:
We analyze Chandra X-ray Observatory imaging of 108 galaxies hosting
nuclear star clusters (NSCs) to search for signatures of massive black
holes (BHs). NSCs are extremely dense stellar environments with
conditions that can theoretically facilitate massive BH formation.
Recent work by Stone+ (2017MNRAS.467.4180S 2017MNRAS.467.4180S) finds that sufficiently
dense NSCs should be unstable to the runaway growth of a stellar-mass
BH into a massive BH via tidal captures. Furthermore, there is a
velocity dispersion threshold (40km/s) above which NSCs should
inevitably form a massive BH. To provide an observational test of
these theories, we measure X-ray emission from NSCs and compare it to
the measured velocity dispersion and tidal capture runaway timescale.
We find that NSCs above the 40km/s threshold are X-ray detected at
roughly twice the rate of those below (after accounting for
contamination from X-ray binaries). These results are consistent with
a scenario in which dense, high-velocity NSCs can form massive BHs,
providing a formation pathway that does not rely on conditions found
only at high redshift.
Description:
Our parent sample contains 207 nearby (D<50Mpc) galaxies hosting
nuclear star clusters (NSCs). All 207 have Hubble Space Telescope
observations.
Chandra X-ray Observatory (CXO) observations were available in the
archive or newly acquired for 108 out of 207 galaxies. Fourteen
objects were targeted with our Chandra program (GO-20700424;
PI Baldassare), and 94 objects were in the CXO ACIS archive.
See Section 3.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 65 108 Sample of 108 galaxies with nuclear star clusters
(NSCs) and CXO observations
table2.dat 65 108 X-ray properties
table3.dat 47 46 X-ray binary contamination assessment
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See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
B/chandra : The Chandra Archive Log (CXC, 1999-2014)
VII/237 : HYPERLEDA. I. Catalog of galaxies (Paturel+, 2003)
J/AJ/127/105 : Nuclear star clusters in spiral galaxies (Boker+, 2004)
J/ApJS/164/334 : ACS Virgo Cluster Survey. VI (Ferrarese+, 2006)
J/ApJ/678/116 : AGNs in nuclear star clusters (Seth+, 2008)
J/A+A/502/91 : Proper motions of stars near SgrA* (Schoedel+, 2009)
J/ApJ/725/670 : Kinematics in the M32 nucleus (Seth, 2010)
J/MNRAS/419/2095 : HMXBs in nearby galaxies (Mineo+, 2012)
J/MNRAS/441/3570 : Nuclear star clusters in spiral galaxies (Georgiev+, 2014)
J/MNRAS/457/2122 : Nuclear star clusters photometric masses (Georgiev+, 2016)
J/ApJ/858/118 : Kinematic data of 3 nearby low-mass galaxies (Nguyen+, 2018)
J/ApJS/243/3 : Chandra observations of SINGS galaxies (Lehmer+, 2019)
J/MNRAS/487/4285 : Variable AGN candidates catalog (Pouliasis+, 2019)
J/ApJ/878/18 : NGVS. XXIII. Nuclear star clusters (Sanchez-Janssen+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Name Object identifier
15- 24 F10.6 deg RAdeg Right Ascension in decimal degrees (J2000)
26- 35 F10.6 deg DEdeg Declination in decimal degrees (J2000)
37- 41 F5.2 mag m-M [27.2/33.6] Distance modulus from
Georgiev+ (2016, J/MNRAS/457/2122)
43- 47 F5.2 Mpc Dist [2.7/50.6] Distance
49- 56 E8.2 yr-1 NTC [3e-14/3.3e-7] Tidal capture rate from
Stone+ (2017MNRAS.467.4180S 2017MNRAS.467.4180S)
58- 63 F6.2 km/s Sigma [6.8/396] Velocity dispersion from
Stone+ (2017MNRAS.467.4180S 2017MNRAS.467.4180S)
65 I1 --- Core [0/1] Core resolved? from
Stone+ (2017MNRAS.467.4180S 2017MNRAS.467.4180S) (1)
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Note (1):
0 = lower limit on tidal capture rate due to the discrete concentration
values used in fitting the light profiles of the NSCs.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Name Object identifier
15- 19 I5 --- ObsID [387/21480] Chandra observation identifier
21- 27 F7.2 ks Exp [1/9583] Exposure time
29- 33 F5.2 [10-7W] L0.5-7 [36.6/42.3]?=0 Log 0.5-7keV luminosity; erg/s
35- 39 F5.2 [10-7W] b_L0.5-7 [35.9/42.1]?=0 Lower boundary limit in L0.5-7
41- 45 F5.2 [10-7W] B_L0.5-7 [36/42.4] Upper boundary limit in L0.5-7
47- 51 F5.2 [10-7W] L2-10 [36.3/42.3]?=0 Log 2-10keV luminosity; erg/s
53- 57 F5.2 [10-7W] b_L2-10 [35.4/42.2]?=0 Lower boundary limit in L2-10
59- 63 F5.2 [10-7W] B_L2-10 [36.3/42.4] Upper boundary limit in L2-10
65 A1 --- Diff Detected X-ray emission was diffuse? (Y)es or
(N)o
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name Object identifier
13- 20 E8.2 Msun Mass [296000000/358000000000] Stellar mass of the
galaxy
22- 27 F6.4 Msun/yr SFR [0.029/2.8] Star formation rate
29- 33 F5.2 [10-7W] LXRB [36.7/39.5] Log 0.5-8 keV expected XRB
luminosity; erg/s (1)
35- 39 F5.2 [10-7W] LS [36.6/42.3] Log 0.5-8 keV detected source
luminosity; erg/s
41- 47 F7.2 --- Ratio [0.09/3982] Ratio of LS/LXRB
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Note (1): Following the scalings derived in Lehmer+ (2019, J/ApJS/243/3).
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 06-Mar-2024