Radiation pressure, absorption and AGN feedback in the Chandra Deep Fields

TL;DR

This study uses deep X-ray and multi-wavelength data to analyze the impact of radiation pressure and dust absorption on AGN properties, supporting models where dust enhances radiation feedback effects.

Contribution

It provides the largest and deepest observational comparison of AGN Eddington ratios and column densities with dust-gas coupling predictions to date.

Findings

Most AGN have low Eddington ratios and high column densities.

Distribution matches the enhanced radiation pressure model predictions.

Supports a scenario linking radiation pressure to black hole-galaxy scaling relations.

Abstract

The presence of absorbing gas around the central engine of Active Galactic Nuclei (AGN) is a common feature of these objects. Recent work has looked at the effect of the dust component of the gas, and how it enhances radiation pressure such that dusty gas can have a lower effective Eddington limit than ionised gas. In this work, we use multi-wavelength data and X-ray spectra from the 2 Ms exposures of the Chandra Deep Field North and Chandra Deep Field South surveys, to characterise the AGN in terms of their Eddington ratio and hydrogen column density. Their distributions are then compared with what is predicted when considering the coupling between dust and gas. Our final sample consists of 234 objects from both fields, the largest and deepest sample of AGN for which this comparison has been made up to date. We find that most of the AGN in our sample tend to be found at low Eddington ratios (typically between 1e-4 and 1e-1) and high column density (>1e22 cm^-2), with black hole masses between ~1e8 and 1e9 solar masses. Their distribution is in agreement with that expected from the enhanced radiation pressure model, avoiding the area where we would predict the presence of outflows. We also investigate how the balance between AGN radiation pressure and gravitational potential influences the behaviour of clouds in the galactic bulge, and describe a scenario where an enhanced radiation pressure can lead to the fundamental plane of black hole/galaxy scaling relations.