A Subhalo‐Galaxy Correspondence Model of Galaxy Biasing

Abstract

We propose a model for allocating galaxies in cosmological N-body simulations. We identify each subhalo with a galaxy and assign luminosity and morphological type, assuming that the galaxy luminosity is a monotonic function of the host subhalo mass. Morphology is assigned using two simple relations between the subhalo mass and galaxy luminosity for different galaxy types. The first uses a constant luminosity ratio between early-type ( E/SO) and late-type (S/Irr) galaxies at a fixed subhalo mass. The other assumes that galaxies of different morphological types but equal luminosity have a constant ratio of subhalo mass. We made a series of comparisons of the properties of these mock galaxies with those of SDSS galaxies. The resulting mock galaxy sample is found to successfully reproduce the observed local number density distribution except in high-density regions. We study the luminosity function as a function of local density, and find that the observed luminosity functions in different local density environments are overall well reproduced by the mock galaxies. A discrepancy is found at the bright end of the luminosity function of early types in the underdense regions and at the faint end of both morphological types in very high density regions. A significant fraction of the observed earlytype galaxies in voids seem to have undergone relatively recent star formation and become brighter. The lack of faint mock galaxies in dense regions may be due to the strong tidal force of the central halo, which destroys less massive satellite subhalos around the simulation. The mass-to-light ratio is found to depend on the local density in a way similar to that observed in the SDSS sample. We have found an impressive agreement between our mock galaxies and the SDSS galaxies in the dependence of central velocity dispersion on the local density and luminosity.

Topology of Luminous Red Galaxies From the Sloan Digital Sky Survey

“…Overall, the HGC galaxy assignment scheme of Kim et al (2008) is able to match the observed amplitudes and shapes of the corresponding genus curves well. In fact, from Table 1, one may note that the values obtained for Δν f , A V , and A C from the simulated LRG samples agree well, within the quoted uncertainties, with those measured from the observational sample.…”

“…The galaxy mass, M gal , should be the halo mass M h corresponding to the g -band galaxy luminosity M g , i.e., M h = f (M g ) (see point 3 in Section 4.2 for more details). Using the LRG cumulative LF measured at the reference redshift bin and the halo cumulative mass function derived from a full cubic data snapshot of HR3 at z = 0.2 (which is compatible with the reference redshift), we apply the halo-galaxy one-toone correspondence model (HGC) of Kim et al (2008) and convert galaxy luminosities into halo masses, and vice versa. Figure 6 shows the relation between galaxy luminosity and halo mass used to determine M gal .…”

Combined Effects of Galaxy Interactions and Large-Scale Environment on Galaxy Properties

“…We assume γ is constant with galaxy luminosity for a given morphological type. The mass-to-light ratio of galaxies is actually expected to be a monotonically increasing function of galaxy halo mass over the luminosity range of our sample (M r < −19.0; see Figures 3 and 4 of Kim et al 2008). Then the overdensity of the high density regions will be underestimated.…”

Horizon Run 4 Simulation: Coupled Evolution of Galaxies and Large-Scale Structures of the Universe

“…The galaxy-subhalo correspondence (or the abundance matching; Kim et al 2008;Trujillo-Gomez et al 2011;Rodríguez-Puebla et al 2013;Reddick et al 2013;Klypin et al 2015) model is positioned between the two aforementioned models. It is much simpler than SAMs but based on more physical processes than the HOD.…”