The Consequences of the Cosmic Star Formation Rate: X-Ray Number Counts

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Abstract
We discuss the observable consequences for the detection of galaxies in the X-ray bandpass resulting from a peak in the cosmic star formation rate at a redshift greater than 1. Following N. White and P. Ghosh, we assume a large evolution in the X-ray/B luminosity ratio at z ~ 0.5-1.5 resulting from the X-ray binaries that have evolved from stars formed at z > 1-2. Using the Hubble Deep Field-North (HDF-N) redshift survey data and the locally observed X-ray/B luminosity ratio as a guide, we estimate a median X-ray flux (2-10 keV) on the order of 8 × 10-18 ergs cm-2 s-1 for galaxies in the HDF-N, which is consistent with a signal derived from a recent stacking analysis of the HDF-N Chandra data by N. Brandt and coworkers. We also predict the number counts in deep X-ray surveys expected from normal galaxies at high redshift.
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