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

Abstract

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