Dissecting the roles of mass and environment quenching in galaxy evolution with EAGLE

TL;DR

This study uses the EAGLE simulation to analyze how galaxy properties like halo mass, stellar mass, and star formation rate are interconnected and how these relationships evolve over cosmic time, highlighting the roles of mass and environment quenching.

Contribution

It identifies the dominant axes of galaxy property correlations using PCA in EAGLE, compares them with SDSS data, and extends the analysis across redshift, revealing consistent physical processes.

Findings

Principal components align with SDSS observations.

Environmental quenching is significant in high-mass haloes.

Mass quenching affects galaxies above 10^10 M_solar regardless of environment.

Abstract

We exploit the pioneering cosmological hydrodynamical simulation, EAGLE, to study how the connection between halo mass (M_halo), stellar mass (M*) and star-formation rate (SFR) evolves across redshift. Using Principal Component Analysis we identify the key axes of correlation between these physical quantities, for the full galaxy sample and split by satellite/central and low/high halo mass. The first principal component of the z=0 EAGLE galaxy population is a positive correlation between M_halo, M* and SFR. This component is particularly dominant for central galaxies in low mass haloes. The second principal component, most significant in high mass haloes, is a negative correlation between M_halo and SFR, indicative of environmental quenching. For galaxies above M*~10^10M_solar, however, the SFR is seen to decouple from the M_halo-M* correlation; this result is found to be independent of environment, suggesting that mass quenching effects are also in operation. We find extremely good agreement between the EAGLE principal components and those of SDSS galaxies; this lends confidence to our conclusions. Extending our study to EAGLE galaxies in the range z=0-4, we find that, although the relative numbers of galaxies in the different subsamples change, their principal components do not change significantly with redshift. This indicates that the physical processes that govern the evolution of galaxies within their dark matter haloes act similarly throughout cosmic time. Finally, we present halo occupation distribution model fits to EAGLE galaxies and show that one flexible 6-parameter functional form is capable of fitting a wide range of different mass- and SFR-selected subsamples.