X-ray probes of cosmic star formation history

We discuss the imprints left by a cosmological evolution of the star format ion rate (SFR) on the evolution of X-ray luminosities L-x of normal galaxie s, using the scheme earlier proposed by us, wherein the evolution of L-x of a galaxy is driven by the evolution of its X-ray binary population. As ind icated in our earlier work, the L-x profile of 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 e volution of X-ray luminosities of galaxies, updating our work by using a su ite of more recently developed SFR profiles that span the currently plausib le range. The first Chandra deep imaging results on L-x evolution are begin ning to probe the SFR profile of bright spiral galaxies; the early results are consistent with predictions based on current SFR models. Using these ne w SFR profiles, the resolution of the "birthrate problem" of low-mass X-ray binaries and recycled, millisecond pulsars in terms of an evolving global SFR is more complete. We discuss the possible impact of the variations in t he SFR profile of individual galaxies and galaxy types.