Modeling Luminosity‐dependent Galaxy Clustering through Cosmic Time

Abstract

We employ high-resolution dissipationless simulations of the concordance ΛCDM cosmology (Ω 0 = 1 - Ω Λ = 0.3, h = 0.7, σ 8 = 0.9) to model the observed luminosity dependence and evolution of galaxy clustering through most of the age of the universe, from z ~ 5 to z ~ 0. We use a simple, nonparametric model, which monotonically relates galaxy luminosities to the maximum circular velocity of dark matter halos ( V max ) by preserving the observed galaxy luminosity function in order to match the halos in simulations with observed galaxies. The novel feature of the model is the use of the maximum circular velocity at the time of accretion, V , for subhalos, the halos located within virial regions of larger halos. We argue that for subhalos in dissipationless simulations, V reflects the luminosity and stellar mass of the associated galaxies better than the circular velocity at the epoch of observation, V . The simulations and our model L - V max relation predict the shape, amplitude, and luminosity dependence of the two-point correlation function in excellent agreement with the observed galaxy clustering in the SDSS data at z ~ 0 and in the DEEP2 samples at z ~ 1 over the entire probed range of projected separations, 0.1 < r p /( h -1 Mpc) < 10.0. In particular, the small-scale upturn of the correlation function from the power-law form in the SDSS and DEEP2 luminosity-selected samples is reproduced very well. At z ~ 3-5, our predictions also match the observed shape and amplitude of the angular two-point correlation function of Lyman break galaxies (LBGs) on both large and small scales, including the small-scale upturn. This suggests that, like galaxies in lower redshift samples, the LBGs are fair tracers of the overall halo population and that their luminosity is tightly correlated with the circular velocity (and hence mass) of their dark matter halos.