Uncovering Local Absorbed Active Galactic Nuclei with Swift and Suzaku

TL;DR

This paper reviews the properties of obscured active galactic nuclei detected by Swift and Suzaku, highlighting their distribution, luminosity differences, and implications for black hole evolution.

Contribution

It provides new insights into the X-ray and optical characteristics of heavily obscured AGN from the Swift survey, including the distribution of absorbed and unabsorbed sources.

Findings

Absorbed AGN are less luminous than unabsorbed sources.

Sources with LINERs/H II regions are the least luminous.

Optical Seyferts have similar luminosity distributions regardless of absorption.

Abstract

Detection of absorbed active galactic nuclei and their properties remains an elusive and important problem in understanding the evolution and activation of black holes. With the very hard X-ray survey conducted by Swift's Burst Alert Telescope - the first all-sky survey in 30 years - we are beginning to uncover the characteristics of obscured AGN. The synergy between Suzaku and Swift has been crucial in pinning down the X-ray properties of newly detected heavily obscured but bright hard X-ray sources. We review the X-ray and optical spectroscopic properties of obscured AGN in the local Universe, as detected in the Swift survey. We discuss the relative distribution of absorbed/unabsorbed sources, including "hidden" and Compton thick AGN populations. Among the results from the survey, we find that absorbed AGN are less luminous than unabsorbed sources. Optical spectra reveal that sources with emission line ratios indicative of LINERs/H II galaxies/composites are the least luminous objects in the sample, while optical absorbed and unabsorbed Seyferts have the same luminosity distributions. Thus, the least luminous sources are likely accreting in a different mode than the Seyferts.