The Relationship Between Eddington Ratio and Column Density in U/LIRG AGN

TL;DR

This study investigates the relationship between Eddington ratio and column density in U/LIRG AGN, suggesting radiation pressure plays a key role in their growth, with initial evidence from a small sample of nine objects.

Contribution

It provides the first analysis of Eddington ratios in IR-selected U/LIRG AGN with dynamical black hole masses, supporting radiation-regulated growth models.

Findings

IR-selected AGN are consistent with radiation pressure-regulated growth.

Limited sample size; larger datasets needed for conclusive results.

IR-selected AGN may host over-massive black holes.

Abstract

The local X-ray AGN population appears to follow a growth cycle regulated by the AGN's own radiation, marked by changes in their obscuration and Eddington ratio during accretion events. Because AGN in infrared-selected galaxies are more likely to be Compton-thick and have evidence for over-massive black holes, we explore whether infrared-selected AGN follow the radiation-regulated AGN growth scheme. We calculate the Eddington ratios of nine U/LIRG AGN with dynamical BH mass measurements, finding that though the number of objects is limited, AGN in IR-selected galaxies appear consistent with radiation pressure-regulated growth. We suggest that enlarging the sample of dynamical BH mass measurements in IR-selected systems will provide more stringent tests of whether their AGN are primarily regulated by radiation pressure.