IN TEG R AL IBIS Extragalactic Survey: Active Galactic Nuclei Selected at 20-100 keV

Abstract

Analysis of International Gamma-Ray Astrophysics Laboratory (INTEGRAL) Core Programme and public open-time observations performed up to 2005 April provides a sample of 62 active galactic nuclei in the 20-100 keV band above a flux limit of ~1.5×10 -11 ergs cm -2 s -1. Most (42) of the sources in the sample are Seyfert galaxies, almost equally divided between type 1 and type 2 objects; six are blazars, and 14 are still unclassified. Excluding the blazars, the average redshift of our sample is 0.021, while the mean luminosity is logL=43.45. We find that absorption is present in 65% of the objects, with 14% of the total sample due to Compton-thick active galaxies. In agreement with both Swift BAT team results and 2-10 keV studies, the fraction of absorbed objects decreases with the 20-100 keV luminosity. All Seyfert 2's in our sample are absorbed, as are 33% of Seyfert 1's. The present data highlight the capability of INTEGRAL to probe the extragalactic gamma-ray sky and to find new and/or absorbed active galaxies. Based on observations obtained with INTEGRAL, an ESA project with instruments and science data center funded by ESA member states (especially the PI countries: Denmark, France, Germany, Italy, Switzerland, Spain), the Czech Republic, and Poland and with the participation of Russia and the US.