On The Nature of Fossil Galaxy Groups

TL;DR

This study introduces a new sample of fossil galaxy groups and compares their properties with non-fossil systems, finding no significant differences and suggesting FGs are a common phase in galaxy group evolution.

Contribution

The paper provides a new sample of fossil groups and demonstrates their properties are similar to non-fossil systems, challenging the idea that FGs are a distinct class.

Findings

Fossil groups have similar X-ray, photometric, and spectroscopic properties to non-fossil systems.

No evidence supports an evolutionary sequence from compact groups to fossil groups.

Fossil groups are likely a common phase in galaxy group evolution, not a separate class.

Abstract

We present a new sample of 25 fossil groups (FGs) at z < 0.1, along with a control sample of seventeen bright ellipticals located in non-fossil systems. Both the global properties of FGs (e.g. X-ray luminosity) as well as the photometric properties (i.e. isophotal shape parameter, a4) and spectroscopic parameters (e.g. the alpha-enhancement) of their first-ranked ellipticals are consistent with those of the control sample. This result favors a scenario where FGs are not a distinct class of systems, but rather a common phase in the life of galaxy groups. We also find no evidence for an evolutionary sequence explaining the formation of galaxies in fossil systems through the merging of galaxies in compact groups.