The Effect of Partial Obscuration on the Luminosity Dependence of the Obscured Fraction in Active Galactic Nuclei

TL;DR

This study investigates how partial obscuration in AGN affects the observed relationship between luminosity and obscured fraction, proposing a model that accounts for complex spectra and partial covering effects.

Contribution

It introduces a model incorporating partial covering to explain the luminosity dependence of obscured AGN fractions, reconciling different observational results.

Findings

The model reproduces the observed luminosity dependence of obscured fractions.

Partial covering significantly impacts apparent AGN luminosities.

The model aligns with observed X-ray and infrared luminosity ratios.

Abstract

Surveys of Active Galactic Nuclei (AGN) in different observational regimes seem to give different answers for the behaviour of the obscured fraction with luminosity. Based on the complex spectra seen in recent studies, we note that partial covering could significantly change the apparent luminosities of many AGN, even after apparent X-ray absorption correction. We explore whether this effect could reproduce the observed dependence of the obscured fraction on the apparent X-ray luminosities seen between 2--10 keV. We can reproduce the observed trend in a model where 33 per cent of AGN are unobscured, 30 per cent are heavily buried, and 37 per cent have a range of intermediate partial coverings. Our model is also tentatively successful at reproducing observed trends in the X-ray vs. infrared luminosity ratio for AGN.