Connecting galaxy evolution in clusters with their radial profiles and phase space distribution: results from the IllustrisTNG hydrodynamical simulations

TL;DR

This study uses the IllustrisTNG simulations to analyze galaxy distributions around clusters, revealing how galaxy evolution affects observable properties like density profiles and phase space, with implications for comparing simulations to real data.

Contribution

It identifies distinct galaxy populations with unique evolutionary signatures and examines their distribution and splashback radii in clusters, linking physical processes to observable features.

Findings

Low-mass red galaxies are most concentrated with the largest splashback radius.

High-mass red galaxies are less concentrated with smaller splashback radius.

Blue galaxies quench rapidly on radial orbits before reaching pericenter.

Abstract

We study the population of galaxies around galaxy clusters in the hydrodynamic simulation suite IllustrisTNG 300-1 to study the signatures of their evolutionary history on observable properties. We measure the radial number density profile, phase space distribution, and splashback radius for galaxies of different masses and colors over the redshift range $z=0-1$. The three primary physical effects which shape the galaxy distribution within clusters are the galaxy quenching, angular momentum distribution and dynamical friction. We find three distinct populations of galaxies by applying a Gaussian mixture model to their distribution in color and mass. They have distinct evolutionary histories and leave distinct signatures on their distribution around cluster halos. We find that low-mass red galaxies show the most concentrated distribution in clusters and the largest splashback radius, while high-mass red galaxies show a less concentrated distribution and a smaller splashback radius. Blue galaxies, which mostly quench into the low-mass red population, have the shallowest distribution within the clusters, with those on radial orbits quenched rapidly before reaching pericenter. Comparison with the distribution of galaxies from the Dark Energy Survey (DES) survey around Sunyaev-Zeldovich (SZ) clusters from the Atacama Cosmology Telescope (ACT) and South Pole Telescope (SPT) surveys shows evidence for differences in galaxy evolution between simulations and data.