Lessons learnt from INTEGRAL AGN

TL;DR

This study analyzes 199 AGN observed by INTEGRAL, confirming the unified model of Seyfert galaxies in hard X-rays and revealing spectral and luminosity differences related to absorption and inclination.

Contribution

It provides the first comprehensive analysis of INTEGRAL AGN data, testing the unified scheme and detailing spectral and luminosity differences between Seyfert types.

Findings

Seyfert 1 and 2 have similar underlying continua with photon index 1.95.

Seyfert 1 are on average twice as luminous in hard X-rays as Seyfert 2.

Spectral differences include flatter spectra and higher cut-off energies in Seyfert 2.

Abstract

The INTEGRAL mission provides a large data set for studying the hard X-ray properties of AGN and allows to test the unified scheme for AGN. We present results based on the analysis of 199 AGN. A difference between the Seyfert types is detected in slightly flatter spectra with higher cut-off energies and lower luminosities for the more absorbed/type 2 AGN. When applying a Compton reflection model, the underlying continua (photon index 1.95) appear the same in Seyfert 1 and 2, and the reflection strength is R=1 in both cases, with differences in the inclination angle only. A difference is seen in the sense that Seyfert 1 are on average twice as luminous in hard X-rays than the Seyfert 2 galaxies. The unified model for Seyfert galaxies seems to hold, showing in hard X-rays that the central engine is the same in Seyfert 1 and 2 galaxies, seen under different inclination angle and absorption. Based on our knowledge of AGN from INTEGRAL data, we briefly outline open questions and investigations to answer them. In this context an ultra-deep (>= 12 Ms) extragalactic field can be a true legacy of the INTEGRAL mission in the area of AGN studies.