Hot Gas Halos in Early-Type Field Galaxies

TL;DR

This study investigates hot gas halos in early-type field galaxies using X-ray observations, revealing that their hot gas content depends on galaxy mass and environment, with internal processes and environmental effects influencing gas retention or loss.

Contribution

It provides new insights into how galaxy environment and mass influence hot gas retention, highlighting differences between field and group/cluster galaxies.

Findings

Field galaxies have steeper L_X-L_K relation than group/cluster galaxies.

Low-mass field galaxies often lack hot gas due to internal feedback processes.

Environmental effects like ram pressure stripping remove hot gas from some group/cluster galaxies.

Abstract

We use Chandra and XMM-Newton to study the hot gas content in a sample of field early-type galaxies. We find that the L_X-L_K relationship is steeper for field galaxies than for comparable galaxies in groups and clusters. The low hot gas content of field galaxies with L_K < L_star suggests that internal processes such as supernovae driven winds or AGN feedback expel hot gas from low mass galaxies. Such mechanisms may be less effective in groups and clusters where the presence of an intragroup or intracluster medium can confine outflowing material. In addition, galaxies in groups and clusters may be able to accrete gas from the ambient medium. While there is a population of L_K < L_star galaxies in groups and clusters that retain hot gas halos, some galaxies in these rich environments, including brighter galaxies, are largely devoid of hot gas. In these cases, the hot gas halos have likely been removed via ram pressure stripping. This suggests a very complex interplay between the intragroup/intracluster medium and hot gas halos of galaxies in rich environments with the ambient medium helping to confine or even enhance the halos in some cases and acting to remove gas in others. In contrast, the hot gas content of more isolated galaxies is largely a function of the mass of the galaxy, with more massive galaxies able to maintain their halos, while in lower mass systems the hot gas escapes in outflowing winds.