INTEGRAL/IBIS deep extragalactic survey: M81, LMC and 3C 273/Coma fields

Abstract

We present results of deep surveys of three extragalactic fields, M81 (exposure of 9.7 Ms), LMC (6.8 Ms) and 3C 273/Coma (9.3 Ms), in the hard X-ray (17-60 keV) energy band with the IBIS telescope onboard the INTEGRAL observatory, based on 12 years of observations (2003-2015). The combined survey reaches a $4\sigma$ peak sensitivity of 0.18 mCrab (2.6$\times$10$^{-12}$ erg s$^{-1}$ cm$^{-2}$) and sensitivity better than 0.25 and 0.87 mCrab over 10% and 90% of its full area of 4900 deg$^{2}$, respectively. We have detected in total 147 sources at $S/N>4\sigma$, including 37 sources observed in hard X-rays for the first time. The survey is dominated by extragalactic sources, mostly by active galactic nuclei (AGN). The sample of identified sources contains 98 AGN (including 64 Seyfert galaxies, 7 LINERs, 3 XBONGs, 16 blazars and 8 AGN of unclear optical class), two galaxy clusters (Coma and Abell 3266), 17 objects located in the Large and Small Magellanic Clouds (13 high- and 2 low-mass X-ray binaries and 2 X-ray pulsars), three Galactic cataclysmic variables, one ultraluminous X-ray source (ULX, M82 X-1) and one blended source (SWIFT J1105.7+5854). The nature of 25 sources remains unknown, so that the surveys identification is currently complete at 83%. We have constructed AGN number-flux relations ($\log{N}$-$\log{S}$) and calculated AGN number densities in the local Universe for the entire survey and for each of the three extragalactic fields.