The starburst-AGN connection: the role of young stellar populations in fueling supermassive black holes

TL;DR

This paper investigates how supernova explosions in circumnuclear regions influence gas inflow and trigger active galactic nuclei, revealing a strong correlation between star formation and black hole activity in obscured AGNs.

Contribution

It introduces a model linking supernova-driven turbulence to gas inflow and AGN activation, supported by analysis of a large sample of type-II AGNs.

Findings

Strong correlation between Eddington ratio and star formation rate.

Supernova explosions facilitate gas inflow by increasing turbulence.

Model explains the observed relation between black hole activity and star formation.

Abstract

Tracing the star formation history in circumnuclear regions (CNRs) is a key step towards understanding the starburst-AGN connection. However, bright nuclei outshining the entire host galaxy prevent the analysis of the stellar populations of CNRs around type-I AGNs. Obscuration of the nuclei by the central torus provides an unique opportunity to study the stellar populations of AGN host galaxies. We assemble a sample of 10, 848 type-II AGNs with a redshift range of $0.03\le z\le 0.08$ from the Sloan Digital Sky Survey's Data Release 4, and measure the mean specific star formation rates (SSFRs) over the past 100Myr in the central $\sim1-2$ kpc . We find a tight correlation between the Eddington ratio ($\lambda$) of the central black hole (BH) and the mean SSFR, strongly implying that supernova explosions (SNexp) play a role in the transportation of gas to galactic centers. We outline a model for this connection by accounting for the role of SNexp in the dynamics of CNRs. In our model, the viscosity of turbulence excited by SNexp is enhanced, and thus angular momentum can be efficiently transported, driving inflows towards galactic centers. Our model explains the observed relation $\lambda \propto \rm SSFR^{1.5-2.0}$, suggesting that AGN are triggered by SNexp in CNRs.