Environment and Gas Fraction in Type-2 AGN versus Non-AGN Galaxies

TL;DR

This study compares the environment and gas content of type-2 AGN and non-AGN galaxies, revealing that AGN activity influences gas reservoirs and star formation, with outflow strength linked to gas fraction and stellar population age.

Contribution

It provides new insights into how AGN activity affects gas content and star formation, highlighting the role of outflows and environment in galaxy evolution.

Findings

AGN host galaxies have lower gas fractions than non-AGN counterparts.

Strong outflows in AGNs are associated with higher gas fractions and younger stars.

Environment has minimal impact on gas fraction and outflow strength.

Abstract

We investigate the environmental parameters and gas fraction (f$_{gas}$) properties of type~2 AGN and non-AGN galaxies, utilizing a large sample of galaxies from SDSS DR7 with z $\le$ 0.3. We find that the environment affects type~2 AGN and non-AGN galaxies in similar ways and does not impact the strength of AGN-driven outflows. The f$_{gas}$ of type~2 AGN and non-AGN host galaxies show no variation between group and isolated environments, suggesting that host galaxy gas content is largely independent of large-scale environment. We find that type~2 AGN host galaxies possess systematically lower f$_{gas}$ than their non-AGN counterparts when matched in stellar mass and star formation rate (SFR). This suggests that AGN activity plays a significant role in regulating the molecular gas reservoir and, consequently, the star formation processes within galaxies. We find that Type~2 AGNs exhibiting strong outflows are associated with higher gas fractions, higher star-formation rates, and younger stellar populations than those with weak or no outflows. This may indicate either concurrent star formation in gas-rich systems hosting powerful outflows, or a time delay between AGN activity and its effect on star formation consistent with a delayed AGN feedback scenario.