Extragalactic source counts in the 20-50 keV energy range from the deep observation of the Coma region by INTEGRAL/IBIS

Preprint
Publisher Website
Google Scholar
  • 6 September 2004
Abstract
We present the analysis of serendipitous sources in a deep, 500 ksec, hard X-ray observation of the Coma cluster region with the IBIS instrument onboard INTEGRAL. We detect 12 serendipitous sources with statistical significance >4sigma and use them to extend the extragalactic source counts in the 20-50 keV energy band down to a limiting flux of 1e-11 erg/s/cm2 (~=1mCrab). This a more than a factor of 10 improvement in sensitivity relative to the previous results in this energy band obtained with the HEAO-1 A4 instrument. The derived source counts are consistent with the Euclidean relation, N(>f) ~ f**-3/2. A large fraction of the detected serendipitous sources are low-redshift, z<0.02 AGNs, mostly of Seyfert 1 type. The surface density of hard X-ray sources is (1.4+-0.5)*10**-2 per square degree above a flux threshold of 1e-11 erg/s/cm2. These sources directly account for 3% of the cosmic X-ray background in the 20-50 keV energy band. Given the low redshift depth of our sample, we expect that similar sources at higher redshifts account for a significant fraction of the hard X-ray background.

This publication has 0 references indexed in Scilit: