AGN-starburst evolutionary connection : a physical interpretation based on radiative feedback

TL;DR

This paper explores how radiation pressure on dust drives AGN feedback, linking dust obscuration with the expulsion of gas and the evolutionary transition from obscured to unobscured quasars.

Contribution

It provides a physical model showing how radiative feedback on dusty gas can explain the AGN-starburst evolutionary sequence.

Findings

Radiative feedback can disrupt dense dusty gas in infrared-optically thick regimes.

Increased dust-to-gas ratio enhances the effective Eddington ratio, promoting gas expulsion.

Dust production in supernovae couples starburst activity with AGN feedback.

Abstract

Observations point towards a close connection between nuclear starbursts, active galactic nuclei (AGN), and outflow phenomena. An evolutionary sequence, starting from a dust-obscured ultra-luminous infrared galaxy and eventually leading to an unobscured optical quasar, has been proposed and discussed in the literature. AGN feedback is usually invoked to expel the obscuring gas and dust in a blow-out event, but the underlying physical mechanism remains unclear. We consider AGN feedback driven by radiation pressure on dust, which directly acts on the obscuring dusty gas. We obtain that radiative feedback can potentially disrupt dense gas in the infrared-optically thick regime, and that an increase in the dust-to-gas fraction leads to an increase in the effective Eddington ratio. Thus the more dusty gas is preferentially expelled by radiative feedback, and the central AGN is prone to efficiently remove its own obscuring dust cocoon. Large amounts of dust imply heavy obscuration but also powerful feedback, suggesting a causal link between dust obscuration and blow-out. In this picture, AGN feedback and starburst phenomena are intrinsically coupled through the production of dust in supernova explosions, leading to a natural interpretation of the observed evolutionary path.