X-Ray Binaries in External Galaxies
Abstract
X-ray appearance of normal galaxies is mainly determined by X-ray binaries powered by accretion onto a neutron star or a stellar mass black hole. Their populations scale with the star-formation rate and stellar mass of the host galaxy and their X-ray luminosity distributions show a significant split between star-forming and passive galaxies, both facts being consequences of the dichotomy between high- and low-mass X-ray binaries. Metallicity, IMF and stellar age dependencies, and dynamical formation channels add complexity to this picture. The numbers of high-mass X-ray binaries observed in star-forming galaxies indicate quite high probability for a massive star to become an accretion powered X-ray source once upon its lifetime. This explains the unexpectedly high contribution of X-ray binaries to the Cosmic X-ray Background, of the order of $\sim 10\%$, mostly via X-ray emission of faint star-forming galaxies located at moderate redshifts which may account for the unresolved part of the CXB. Cosmological evolution of the $L_X-{\rm SFR}$ relation can make high-mass X-ray binaries a potentially significant factor in (pre)heating of intergalactic medium in the early Universe.
- Publication:
-
Handbook of X-ray and Gamma-ray Astrophysics
- Pub Date:
- 2022
- DOI:
- 10.1007/978-981-16-4544-0_108-1
- arXiv:
- arXiv:2304.14080
- Bibcode:
- 2022hxga.book..105G
- Keywords:
-
- Astrophysics - High Energy Astrophysical Phenomena;
- Astrophysics - Cosmology and Nongalactic Astrophysics;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- Invited chapter for the Handbook of X-ray and Gamma-ray Astrophysics. Editors: Cosimo Bambi, Andrea Santangelo. Publisher: Springer Singapore, 2023