Compact groups from semi-analytical models of galaxy formation -- IV: effect of group assembly on the evolution of their galaxies

TL;DR

This study uses semi-analytical models to analyze how the assembly history of compact galaxy groups influences the evolution and properties of their member galaxies over cosmic time.

Contribution

It demonstrates that the assembly channel of compact groups significantly affects galaxy evolution, highlighting galaxy assembly bias and providing a new classification approach.

Findings

High-mass CG galaxies have little cold gas for the last 8 Gyr.

Low-mass CG galaxies still retain some cold gas today.

Groups with earlier assembly show more gas loss and star formation suppression.

Abstract

Using over 3000 compact groups (CGs) of galaxies extracted from mock catalogues built from semi-analytical models of galaxy formation (SAMs), we study whether the CG assembly channel affects the z=0 properties of galaxies and their evolution. The evolution of CG galaxy properties with time is a clear function of their stellar masses. For instance, high-stellar-mass CG galaxies have lived their last 8 Gyr with little cold gas content while maintaining their reservoir of hot gas, while low-mass CG galaxies still preserve some of their cold gas content at the present but they have completely drained their hot gas reservoir. Beyond that, we find that the evolution of CG galaxies is also a function of the assembly history of the CGs: with more extreme losses of gas content, faster mass gain rates for black holes and more marked suppression of star formation as a function of cosmic time as we go from recent to early CG assembly. Thus, CGs constitute another laboratory for galaxy assembly bias, as the later assembling groups have later star formation. Our results show that classifying CGs according to their assembly channel is a way of distinguishing different paths by which galaxies transform their properties throughout their history.