The Distribution of AGN Covering Factors

TL;DR

This paper reviews the properties and distribution of the obscuring regions in AGN, revealing complex, multi-scale structures with a potentially simple underlying distribution influenced by random misalignments.

Contribution

It provides new evidence on the distribution of AGN covering factors based on a large sample of quasars, challenging previous assumptions about their simplicity and symmetry.

Findings

Obscuring regions are more complex and multi-scale than previously thought.

Covering factor distribution shows no dependence on luminosity.

Random misalignments may explain the distribution of covering factors.

Abstract

We review our knowledge of the most basic properties of the AGN obscuring region - its location, scale, symmetry, and mean covering factor - and discuss new evidence on the distribution of covering factors in a sample of ~9000 quasars with WISE, UKIDSS, and SDSS photometry. The obscuring regions of AGN may be in some ways more complex than we thought - multi-scale, not symmetric, chaotic - and in some ways simpler - with no dependence on luminosity, and a covering factor distribution that may be determined by the simplest of considerations - e.g. random misalignments.