2014A&A...567A...2D


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.10CEST02:17:07

2014A&A...567A...2D - Astronomy and Astrophysics, volume 567A, 2-2 (2014/7-1)

Luminosity function of low-mass X-ray binaries in the globular cluster system of NGC 1399.

D'AGO G., PAOLILLO M., FABBIANO G., PUZIA T.H., MACCARONE T.J., KUNDU A., GOUDFROOIJ P. and ZEPF S.E.

Abstract (from CDS):

We present a study of the faint end of the X-ray luminosity function (XLF) of low-mass X-ray binaries (LMXBs) in the Globular Cluster (GC) system of the cD galaxy NGC 1399.We performed a stacking experiment on 618 X-ray undetected GCs, in order to verify the presence of faint LMXBs and to constrain the faint-end slope of the GC-LMXBs XLF below the individual detection threshold of 8x1037erg/s in the 0.5-8keV band. We obtain a significant X-ray detection for the whole GC sample, as well as for the red and blue GC subpopulations, corresponding to an average luminosity per GC <LX>GC of (3.6±1.0)x1036erg/s, (6.9±2.1)x1036erg/s, and (1.7±0.9)x1036erg/s, respectively, for all GCs, red GCs, and blue GCs. If LMXBs in red and blue GCs have the same average intrinsic luminosity, we derive a red/blue ratio ≃3 of GCs hosting LMXBs (2.5±1.0 or 4.1±2.5 depending on the surveyed region); alternatively, assuming the fractions observed for brighter sources, we measure an average X-ray luminosity of LX=(4.3±1.3)x1037erg/s and LX=(3.4±1.7)x1037erg/s per red and blue GC-LMXBs, respectively. In the assumption that the XLF follows a power-law distribution, we find that a low-luminosity break is required at LX≤8x1037erg/s both in the whole, as well as in the color-selected (red and blue) subsamples. Given the bright-end slopes measured above the X-ray completeness limit, this result is significant at >3σ level. Our best estimates for the faint-end slope are βL=-1.39/-1.38/-1.36 for all/red/blue GC-LMXBs. We also find evidence that the luminosity function becomes steeper at luminosities LX> 3x1039erg/s, as observed in old ellipticals.If most GCs host a single X-ray binary, we conclude that in NGC 1399 the XLF flattens at low luminosities as observed in other nearer galaxies, and we discuss some consequences of this flattening on LMXBs formation scenarios.

Abstract Copyright:

Journal keyword(s): X-rays: binaries - X-rays: galaxies - galaxies: elliptical and lenticular, cD - galaxies: individual: NGC 1399

Simbad objects: 11

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Number of rows : 11

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 M 31 G 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 10904 1
2 LBN 659 GiG 02 36 35.469 +59 39 16.53   17       ~ 175 2
3 NGC 1399 BiC 03 38 29.083 -35 27 02.67 11.05 9.74 9.59 8.12   ~ 1449 1
4 ACO S 373 ClG 03 38 30 -35 27.3           ~ 1538 0
5 M 81 Sy2 09 55 33.17306143 +69 03 55.0609270   7.89 6.94     ~ 3965 5
6 M 105 LIN 10 47 49.600 +12 34 53.87   10.56 9.76 9.12 8.18 ~ 1380 0
7 NGC 4278 LIN 12 20 06.82563 +29 16 50.7124 11.54 11.09 10.16     ~ 888 2
8 NAME Vir I ClG 12 26 32.1 +12 43 24   10.00 8.49     ~ 5825 0
9 NGC 4697 GiG 12 48 35.8992791100 -05 48 02.497675635   10.97   9.83   ~ 804 0
10 NAME Centaurus A Sy2 13 25 27.61509104 -43 01 08.8056025   8.18 6.84 6.66   ~ 3999 3
11 M 51 GiP 13 29 52.698 +47 11 42.93   9.26 8.36 8.40   ~ 3782 4

    Equat.    Gal    SGal    Ecl

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2020.07.10-02:17:07

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