X-ray Observations of Optically Selected Giant Elliptical-Dominated Galaxy Groups

TL;DR

This study combines optical and X-ray data to analyze three galaxy groups with giant ellipticals, revealing one as a fossil group and providing insights into their evolutionary stages.

Contribution

It offers new combined optical and X-ray analysis of optically selected galaxy groups, identifying a fossil group and characterizing the evolutionary status of others.

Findings

One system qualifies as a fossil group.

Two systems have a significant magnitude gap but are not fossil groups.

The analysis enhances understanding of galaxy group evolution.

Abstract

We present a combined optical and X-ray analysis of three optically selected X-ray bright groups with giant elliptical galaxies in the center. These massive ellipticals were targeted for XMM-Newton X-ray observations based on their large velocity dispersions and their proximity to a nearby ROSAT X-ray source. Additionally, these targets are significantly brighter in the optical than their nearest neighbors. We show that one of these systems meets the standard criteria for a fossil group. While the other two systems have a prominent magnitude gap in the E/S0 ridgeline, they do not appear to have reached the fossil-like final stage of group evolution.