The Halo Occupation Number and Spatial Distribution of 2dF Galaxies

Abstract

We use the clustering results obtained by Madgwick et al. (2003) for a sample of 96,791 2dF galaxies with redshift 0.01<z<0.15 to study the distribution of late-type and early-type galaxies within dark matter haloes of different mass. The adopted method relies on the connection between the distribution of sources within haloes and their clustering properties by focusing on the issue of the halo occupation function i.e. the probability distribution of the number of galaxies brighter than some luminosity threshold hosted by a virialized halo of given mass. Within this framework, the distribution of galaxies within haloes is shown to determine galaxy-galaxy clustering on small scales, being responsible for the observed power-law behaviour at separations r≲3 Mpc. For a more extended analysis, we refer the reader to Magliocchetti & Porciani (2003).