Quantifying the role of ram pressure stripping of galaxies within galaxy groups

TL;DR

This study challenges the belief that ram pressure stripping is rare in galaxy groups by identifying 45 candidates, suggesting it could be a key mechanism for galaxy quenching in such environments.

Contribution

It provides observational evidence and a physical model showing ram pressure stripping occurs in galaxy groups, not just clusters, and may be a dominant quenching process.

Findings

45 ram-pressure stripped galaxy candidates identified

Candidates are mostly blue, star-forming, first infallers

Ram pressure stripping is plausible at group halo masses

Abstract

It is often stated that the removal of gas by ram pressure stripping of a galaxy disk is not a common process in galaxy groups. In this study, with the aid of an observational classification of galaxies and a simple physical model, we show that this may not be true. We examined and identified 45 ram-pressure stripped galaxy candidates from a sample of 1311 galaxy group members within 125 spectroscopically-selected galaxy groups. 13 of these galaxies are the most secure candidates with multiple distinct features. These candidate ram pressure stripped galaxies have similar properties to those found in clusters -- they occur at a range of stellar masses, are largely blue and star-forming and have phase-space distributions consistent with being first infallers into their groups. The only stand-out feature of these candidates is they exist not in clusters, but in groups, with a median halo mass of 10$^{13.5}$ M$_\odot$. Although this may seem surprising, we employ an analytic model of the expected ram pressure stripping force in groups and find that reasonable estimates of the relevant infall speeds and intragroup medium content would result in ram pressure stripped galaxies at these halo masses. Finally, given the considerable uncertainty on the lifetime of the ram-pressure phase, this physical mechanism could be the dominant quenching mechanism in galaxy groups, if our ram pressure stripped candidates can be confirmed.