The impact of cosmic voids on AGN activity

Abstract

From the Eagle project, we study the properties of galaxies hosting AGN in cosmic voids and their surrounding structures, filaments and walls, at $z=0$, comparing them to non-AGN galaxies in similar environments. We found that the AGN fraction decreases as a function of void-centric distance, with void galaxies displaying the highest AGN fraction (12\%), and galaxies in denser environments, showing the lowest AGN fraction (6.7\%), consistent with observations. The AGN fraction is particularly high in most massive void galaxies when controlling for stellar mass. When comparing AGN host galaxies to inactive ones, we find that AGN galaxies tend to have slightly more massive SMBHs, higher specific star formation rates, and reside in higher-mass haloes at a given stellar mass than non-AGN galaxies. At $\rm M_{*} > \rm 10^{10.2} \rm M_{\odot}$, AGN hosts in voids tend to have slightly more massive SMBHs than those in denser environments. Otherwise, the AGN population does not show a clear trend in relation to the global environment. In contrast, non-AGN void galaxies host more massive SMBHs, slightly higher sSFRs, and are located in more massive haloes than those in denser environments. Analysing the recent merger histories of both AGN and non-AGN populations, we find that a larger fraction of massive AGN galaxies have undergone major mergers compared to non-AGN galaxies, regardless of environment. Notably, AGN galaxies in voids show a higher frequency of recent mergers, especially major mergers, than their counterparts in other environments, especially at high stellar mass. Our results suggest that the evolution of SMBHs in voids is closely related to that of their host galaxies and their surrounding environment, while the most recent AGN activity is more strongly linked to recent interactions.