Study of populations of low-mass X-ray binaries in elliptical galaxies

The aim of this thesis is to study the environmental dependence of populations of low-mass X-ray binaries (LMXBs) in early-type galaxies. The dissertation is mainly based on archival data of the Chandra observatory whose unprecedented sub-arcsec angular resolution made it possible to resolve individual compact sources in nearby galaxies. The Chandra data is complemented by the infrared data of the Spitzer observatory as well as by the results of the Hubble Space Telescope and ground based optical observations. The dissertation investigates the dependence of LMXB populations on the stellar density, velocity dispersion and the age of the stellar population. To investigate the LMXB dependence on the stellar density and velocity dispersion , we studied different sub populations of low-mass X-ray binaries – dynamically formed systems in globular clusters and in the nucleus of M31, and presumably pri-mordial X-ray binaries in the fields of galaxies. Our sample includes seven nearby galaxies (M31, Maffei1, Centaurus A, M81, NGC 3379, NGC 4697 and NGC 4278) and the Milky Way, which together provide relatively uniform coverage down to the unprecedented luminosity limit of 10 35 erg/s. In total we have detected 185 LMXBs associated with globular clusters, 35 X-ray sources in the nucleus of M31 and 998 field sources of which ∼ 365 are expected to be background active galac-tic nuclei. We combine these data, taking special care of accurate incompleteness correction and removal of background contamination, and produce luminosity distributions of X-ray binaries in different environments to far greater accuracy than have been previously obtained. We found that the luminosity distributions of globular cluster and field LMXBs differ throughout the entire luminosity range. The fraction of faint (log(L X) < 37) sources in globular clusters is ∼ 4 times smaller than in the field population. This may present a challenge for the models suggesting that the entire LMXB population was formed dynamically in globular clusters and then expelled to the field due to dynamical interactions or as globular clusters dissolve. The luminosity function of dynamically formed sources in the nucleus of M31 is similar to that of globular cluster sources at the faint end but differs at the bright end, that the M31 nucleus hosting significantly fewer bright sources than globular clusters (and field population). The difference between their luminosity distributions is likely caused by the factor of ∼ 10 − 20 difference in stellar velocities in globular clusters and galactic nuclei, which …