Testing the origin of the gamma-ray background

Abstract

Fluctuations of the gamma-ray background (GRB) are investigated. It is assumed that the GRB is produced by discrete sources. Two basic classes of objects as dominant contributors to the GRB are considered: a) blazars and b) starburst galaxies. Predicted logN-logS counts are calculated for these two models. To produce substantial fraction of the XRB, both classes of sources are subject to strong evolution. Since blazars are several orders of magnitude more luminous than starburst galaxies, their number required to produce the GRB is much smaller than the number of starburst galaxies. In effect, fluctuations of the GRB in the blazar model are relatively high. It is shown that moderate improvement in the measurements of the GRB flux will allow us to discriminate beteween these models.