X-Ray Probes of Cosmic Star-Formation History

Pranab Ghosh, Nicholas E. White

Published 2001-08-14Version 1

We discuss the imprints left by a cosmological evolution of the star formation rate (SFR) on the evolution of X-ray luminosities Lx of normal galaxies, using the scheme proposed by White and Ghosh (1998, WG98), wherein the evolution of Lx of a galaxy is driven by the evolution of its X-ray binary population. As indicated in WG98, the profile of Lx with redshift can both serve as a diagnostic probe of the SFR profile and constrain evolutionary models for X-ray binaries. We report here the first calculation of the expected evolution of X-ray luminosities of galaxies, updating the WG98 work by using a suite of more recently developed SFR profiles that span the currently plausible range. The first Chandra deep imaging results on Lx are beginning to probe the SFR profile of bright spirals: the early results are consistent with predictions based on current SFR models. Using these new SFR profiles, the resolution of the ``birthrate problem'' of low-mass X-ray binaries (LMXBs) and recycled, millisecond pulsars (WG98) in terms of an evolving global SFR is more complete. We discuss the possible impact of the variations in the SFR profile of individual galaxies and galaxy-types.