Exploring the AGN-ram pressure stripping connection in local clusters

TL;DR

This study investigates the link between ram-pressure stripping and AGN activity in cluster galaxies, finding a significantly higher AGN incidence in stripped galaxies, especially at higher stellar masses, supporting a potential causal connection.

Contribution

It provides the first robust statistical evidence of an increased AGN fraction in ram-pressure stripped galaxies using a large sample and comparison with non-stripped galaxies.

Findings

AGN fraction in stripped galaxies is ~27% overall.

AGN fraction increases to 51% for galaxies with stellar mass ≥10^10 M_sun.

Significantly higher AGN incidence in stripped galaxies compared to non-stripped ones.

Abstract

Ram-pressure stripping by the intracluster medium (ICM) is one of the most advocated mechanisms that affect the properties of cluster galaxies. A recent study based on a small sample has found that many galaxies showing strong signatures of ram-pressure stripping also possess an active galactic nucleus (AGN), suggesting a possible correlation between the two phenomena. This result has not been confirmed by a subsequent study. Building upon previous findings, here we combine MUSE observations conducted within the GASP program and a general survey of the literature to robustly measure the AGN fraction in cluster's ram pressure stripped galaxies using BPT emission line diagrams. Considering a sample of 115 ram pressure stripped galaxies with stellar masses $\geq 10^9 \, M_{\odot}$, we find an AGN fraction of $\sim27\%$. This fraction strongly depends on stellar mass: it raises to 51% when only ram-pressure stripped galaxies of masses $M_* \geq 10^{10} \, M_{\odot}$ are considered. We then investigate whether the AGN incidence is in excess in ram pressure stripped galaxies compared to non-stripped galaxies, using as comparison a sample of non-cluster galaxies observed by the survey MaNGA. Considering mass-matched samples, we find that the incidence of AGN activity is significantly higher (at a confidence level $>99.95\%$) when ram-pressure stripping is on act, supporting the hypothesis of an AGN-ram pressure connection.