Revealing the galaxy-halo connection in IllustrisTNG


Bose S, Eisenstein DJ, Hernquist L, Pillepich A, Nelson D, Marinacci F, Springel V, Vogelsberger M. Revealing the galaxy-halo connection in IllustrisTNG. Monthly Notices of the Royal Astronomical Society [Internet]. 2019;490 :5693-5711.

Date Published:

December 01, 201


We use the IllustrisTNG (TNG) simulations to explore the galaxy-haloconnection as inferred from state-of-the-art cosmological,magnetohydrodynamical simulations. With the high-mass resolution andlarge volume achieved by combining the 100 Mpc (TNG100) and 300 Mpc(TNG300) volumes, we establish the mean occupancy of central andsatellite galaxies and their dependence on the properties of the darkmatter haloes hosting them. We derive best-fitting HOD parameters fromTNG100 and TNG300 for target galaxy number densities of \bar{n}_g =0.032 and \bar{n}_g = 0.016 h^3 Mpc-3, respectively,corresponding to a minimum galaxy stellar mass of M_\star ̃ 1.9× 10^9and M_\star ̃ 3.5× 10^9 M_☉, respectively, in hosts more massive than10^{11} M_☉. Consistent with previous work, we find that haloes locatedin dense environments, with low concentrations, later formation times,and high angular momenta are richest in their satellite population. Atlow mass, highly concentrated haloes and those located in overdenseregions are more likely to contain a central galaxy. The degree ofenvironmental dependence is sensitive to the definition adopted for thephysical boundary of the host halo. We examine the extent to whichcorrelations between galaxy occupancy and halo properties areindependent and demonstrate that HODs predicted by halo mass andpresent-day concentration capture the qualitative dependence on theremaining halo properties. At fixed halo mass, concentration is a strongpredictor of the stellar mass of the central galaxy, which may play adefining role in the fate of the satellite population. The radialdistribution of satellite galaxies, which exhibits a universal formacross a wide range of host halo mass, is described accurately by thebest-fitting NFW density profile of their host haloes.