INTEGRAL All-Sky Survey: Deep inside Galaxy and beyond

Abstract

This report is related to a hard X-ray survey covering the whole sky performed with the INTEGRAL observatory during seven years. We present the improved method for image reconstruction with IBIS coded mask telescope. The main improvements are related to suppression of systematic effects which strongly limit sensitivity in the region of the Galactic Plane (GP), especially in the crowded field of the Galactic Center (GC). We extended the IBIS/ISGRI background model to take into account Galactic Ridge X-ray Emission (GRXE). To suppress residual systematic artifacts on the reconstructed sky image we apply nonparametric sky image filtering based on wavelet decomposition. The implemented modifications of the sky reconstruction method decreases the systematic noise by _s13_s178764_s19 44% in the region of the GC and practically removes it from high-latitude sky images, leaving sensitivity in the only dependence from Poisson statistics. This allows one to conduct all-sky survey with a highest available at the moment sensitivity in Galactic Plane: 3.7×10_s13_s178722_s1912 erg s_s13_s178722_s191 cm_s13_s178722_s192 _s13_s178764_s19 0.26 mCrab at a 5s detection level in the 17_s13_s178722_s1960 keV working energy band. The survey covers 90% of the sky down to flux limit of 6.2×10_s13_s178722_s1911 erg s_s13_s178722_s191 cm_s13_s178722_s192 (_s13_s178764_s19 4.32 mCrab) and 10% of the sky area down to flux limit of 8.6×10_s13_s178722_s1912 erg s_s13_s178722_s191 cm_s13_s178722_s192 (_s13_s178764_s19 0.60 mCrab).