1306.5761 (Arnau Pujol et al.)

Are the halo occupation predictions consistent with large scale clustering in galaxy simulations?    [PDF]

Arnau Pujol, Enrique Gaztañaga

We study how well we can reconstruct the 2-point clustering of galaxies on linear scales, as a function of mass and luminosity, using the halo (and subhalo) occupation distribution (HOD) in several semi-analytical models of galaxy formation from the Millennium Simulation. In general we find that the reconstruction works at best to 5% accuracy: it underestimates (overestimates) the bias for bright (faint) galaxies. We find that HOD with Friends of Friends groups can reproduce galaxy clustering better than gravitationally bound haloes (main haloes). This indicates that Friends of Friends groups are more directly related to the clustering of these regions than the bound particles in spherical overdensities. However, the reconstruction does not work using subhaloes. This effect is due to the strong environmental dependence on the host halo substructure that distorts the mass dependence of subhalo clustering. We have also found that the reconstructions of galaxy bias from the HOD model fails for low mass haloes with M < 10^11 Msun. We find that this is because galaxy clustering in these simulations does not seem to depend strongly on halo mass for these low masses.

View original: http://arxiv.org/abs/1306.5761