The Epoch of Assembly of Two Galaxy Groups: A comparative study

TL;DR

This study compares the assembly epochs of the Local Group and M81 galaxy group using satellite gas deficiency profiles, revealing that the more gas-rich M81 group assembled later than the Local Group.

Contribution

It introduces an expanded evolutionary model to estimate galaxy group assembly epochs based on satellite gas deficiency profiles, applied to both the Local Group and M81.

Findings

Local Group assembled at z<10

M81 group assembled at z<1-3

Gas deficiency profiles reflect assembly history

Abstract

Nearby galaxy groups of comparable mass to the Local Group show global variations that reflect differences in their evolutionary history. Satellite galaxies in groups have higher levels of gas deficiency as the distance to their host decreases. The well established gas deficiency profile of the Local Group reflects an epoch of assembly starting at z<10. We investigate whether this gas deficiency profile can be used to determine the epoch of assembly for other nearby groups. We choose the M81 group as this has the most complete inventory, both in terms of membership and multi-wavelength observations. We expand our earlier evolutionary model of satellite dwarf galaxies to not only confirm this result for the Local Group but show that the more gas-rich M81 group is likely to have assembled at a later time (z<1-3).