Quenching of Satellite Galaxies at the Outskirts of Galaxy Clusters

TL;DR

This study uses cosmological simulations and an analytic model to show that satellite galaxies experience gas stripping and quenching primarily outside the inner cluster regions, explaining the presence of quenched disc galaxies at cluster outskirts.

Contribution

It provides a detailed analysis of ram pressure stripping effects on satellite galaxies at different cluster radii, highlighting the importance of halo gas removal in star formation quenching.

Findings

Significant gas removal from star-forming discs occurs within 0.5 R_vir.

Halo gas stripping can happen between R_vir and R_shock.

Star formation quenching due to halo gas removal takes 2-3 Gyr.

Abstract

We find, using cosmological simulations of galaxy clusters, that the hot X-ray emitting intra-cluster medium (ICM) enclosed within the outer accretion shock extends out to $R_{\rm shock}\sim(2 - 3) R_{\rm vir}$, where $R_{\rm vir}$ is the standard virial radius of the halo. Using a simple analytic model for satellite galaxies in the cluster, we evaluate the effect of ram pressure stripping on the gas in the inner discs and in the haloes at different distances from the cluster centre. We find that significant removal of star-forming disc gas occurs only at $r \lesssim 0.5 R_{\rm vir}$, while gas removal from the satellite halo is more effective and can occur when the satellite is found between $ R_{\rm vir}$ and $R_{\rm shock}$. Removal of halo gas sets the stage for quenching of the star formation by starvation over $2\textrm{--}3\,\mathrm{Gyr}$, prior to the satellite entry to the inner cluster halo. This scenario explains the presence of quenched galaxies, preferentially discs, at the outskirts of galaxy clusters, and the delayed quenching of satellites compared to central galaxies.