J/MNRAS/446/470 ULX candidates in luminous infrared galaxies (Luangtip+, 2015)
A deficit of ultraluminous X-ray sources in luminous infrared galaxies.
Luangtip W., Roberts T.P., Mineo S., Lehmer B.D., Alexander D.M.,
Jackson F.E., Goulding A.D., Fischer J.L.
<Mon. Not. R. Astron. Soc., 446, 470-492 (2015)>
=2015MNRAS.446..470L 2015MNRAS.446..470L (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, IR ; X-ray sources
Keywords: accretion, accretion discs - black hole physics -
galaxies: starburst - infrared: galaxies - X-rays: binaries
Abstract:
We present results from a Chandra study of ultraluminous X-ray sources
(ULXs) in a sample of 17 nearby (DL<60Mpc) luminous infrared
galaxies (LIRGs), selected to have star formation rates (SFRs) in
excess of 7M☉/yr and low foreground Galactic column densities
(NH≲5x1020cm-2). A total of 53 ULXs were detected and we
confirm that this is a complete catalogue of ULXs for the LIRG sample.
We examine the evolution of ULX spectra with luminosity in these
galaxies by stacking the spectra of individual objects in three
luminosity bins, finding a distinct change in spectral index at
luminosity ∼2x1039erg/s. This may be a change in spectrum as
10M☉ black holes transit from an ∼ Eddington to a
super-Eddington accretion regime, and is supported by a plausible
detection of partially ionized absorption imprinted on the spectrum of
the luminous ULX (LX∼5x1039erg/s) CXOU J024238.9-000055 in
NGC 1068, consistent with the highly ionized massive wind that we
would expect to see driven by a super-Eddington accretion flow. This
sample shows a large deficit in the number of ULXs detected per unit
SFR (0.2 versus 2 ULXs, per M☉/yr) compared to the detection
rate in nearby (DL<14.5Mpc) normal star-forming galaxies. This
deficit also manifests itself as a lower differential X-ray luminosity
function normalization for the LIRG sample than for samples of other
star-forming galaxies. We show that it is unlikely that this deficit
is a purely observational effect. Part of this deficit might be
attributable to the high metallicity of the LIRGs impeding the
production efficiency of ULXs and/or a lag between the star formation
starting and the production of ULXs; however, we argue that the
evidence - including very low NULX/LFIR, and an even lower ULX
incidence in the central regions of the LIRGs - shows that the main
culprit for this deficit is likely to be the high column of gas and
dust in these galaxies, that fuels the high SFR but also acts to
obscure many ULXs from our view.
Description:
In this paper, we study the ULX population hosted by the sample of 17
LIRGs studied in Lehmer et al. (2010ApJ...724..559L 2010ApJ...724..559L), using Chandra
X-ray observations. In brief, this sample was selected as all LIRGs
within a luminosity distance (DL) of 60Mpc with a foreground Galactic
column density (NH)<5x1020cm-2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 80 53 ULX candidates detections, ordered by
right ascension
tablea2.dat 78 86 Less luminous X-ray point sources
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See also:
J/A+A/452/739 : ULX sources and FIRST radio sources (Sanchez-Sutil+, 2006)
J/ApJ/649/730 : ULX population in nearby galaxies from XMM (Winter+, 2006)
J/ApJ/664/458 : Spectral fit of ULX sources (Devi+, 2007)
J/ApJ/687/471 : Observational comparison between ULXs & XRBs (Berghea+, 2008)
J/ApJ/741/49 : ULX candidates in nearby galaxies (Swartz+, 2011)
J/AJ/143/144 : ULX candidates in nearby Arp galaxies (Smith+, 2012)
Byte-by-byte Description of file: tablea1.dat tablea2.dat
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Bytes Format Units Label Explanations
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1- 2 I2 h RAh Right ascension (J2000) of candidate ULX
4- 5 I2 min RAm Right ascension (J2000) of candidate ULX
7- 8 I2 s RAs Right ascension (J2000) of candidate ULX
10 A1 --- DE- Declination sign (J2000) of candidate ULX
11- 12 I2 deg DEd Declination (J2000) of candidate ULX
14- 15 I2 arcmin DEm Declination (J2000) of candidate ULX
17- 18 I2 arcsec DEs Declination (J2000) of candidate ULX
20- 27 A8 --- Host Host galaxy name
29- 35 F7.2 ct NetCt Net photon counts in 0.3-10keV energy band
37- 41 F5.2 ct E_NetCt Error on NetCt (upper value)
43- 47 F5.2 ct e_NetCt Error on NetCt (lower value)
49- 53 F5.2 10-17W/m2 Flux Source flux in 0.3-10keV energy band
55- 58 F4.2 10-17W/m2 E_Flux Error on Flux (upper value)
60- 63 F4.2 10-17W/m2 e_Flux Error on Flux (lower value)
65- 68 F4.2 10+32W Lum Source luminosity, assuming the source is
at the distance of the host galaxy
70- 73 F4.2 10+32W E_Lum Error on Lum (upper value)
75- 78 F4.2 10+32W e_Lum Error on Lum (lower value)
80 I1 --- Notes ? Notes (1)
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Note (1): Notes as follows:
1 = CXOU J024238.9-000055 (Smith & Wilson, 2003ApJ...591..138S 2003ApJ...591..138S,
Cat. J/ApJ/591/138)
2 = This ULX is coincident with a radio source detection. This may be related
to the ULX; it may be an unrelated radio supernova in the host galaxy; or
it might be a background AGN (Ulvestad 2009AJ....138.1529U 2009AJ....138.1529U; Neff,
Ulvestad & Teng 2004ApJ...611..186N 2004ApJ...611..186N; Huang et al. 1990IAUC.4988....0H 1990IAUC.4988....0H).
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 10-Jun-2015