Swift-XRT observation of 34 new INTEGRAL/IBIS AGNs: discovery of Compton thick and other peculiar sources

TL;DR

This study uses Swift-XRT follow-up observations to identify and analyze 34 AGNs detected by INTEGRAL/IBIS, revealing their spectral properties, absorption levels, and discovering peculiar and Compton-thick sources, enhancing understanding of high-energy AGNs.

Contribution

First comprehensive spectral analysis of 34 INTEGRAL/IBIS AGNs using Swift/XRT data, including identification of Compton-thick and peculiar sources and development of a new diagnostic tool.

Findings

Mean photon index of 1.88 with small dispersion.

47% of sources are absorbed with N_H > 10^{22} cm^{-2}.

Identification of at least three Compton-thick AGN candidates.

Abstract

For a significant number of the sources detected at high energies (>10 keV) by the INTEGRAL/IBIS and Swift/BAT instruments there is either a lack information about them in the 2-10 keV range or they are totally unidentified. Herein, we report on a sample of 34 IBIS AGN or AGN candidate objects for which there is X-ray data in the Swift/XRT archive. Thanks to these X-ray follow up observations, the identification of the gamma ray emitters has been possible and the spectral shape in terms of photon index and absorption has been evaluated for the first time for the majority of our sample sources. The sample, enlarged to include 4 more AGN already discussed in the literature, has been used to provide photon index and column density distribution. We obtain a mean value of 1.88 with a dispersion of 0.12, i.e. typical of an AGN sample. Sixteen objects (47%) have column densities in excess of 10^{22} cm^{-2} and, as expected, a large fraction of the absorbed sources are within the Sey 2 sample. We have provided a new diagnostic tool (NH versus F(2-10)keV/F(20-100)keV softness ratio) to isolate peculiar objects; we find at least one absorbed Sey 1 galaxy, 3 Compton thick AGN candidates; and one secure example of a "true" type 2 AGN. Within the sample of 10 still unidentified objects, 3 are almost certainly AGN of type 2; 3 to 4 have spectral slopes typical of AGN; and two are located high on the galactic plane and are strong enough radio emitters so that can be considered good AGN candidates.