The clustering of galaxies in hierarchical galaxy formation models

Abstract

Galaxy clustering encodes information about the values of cosmological parameters and also about the physical processes behind galaxy formation and evolution. The GALFORM semi-analytical model is the theoretical approach we used to model galaxy formation. We start by studying the luminosity dependence of galaxy clustering which is measured accurately in the local Universe. We have compared the clustering predictions of three publicly available galaxy formation models with clustering measurements from the 2dFGRS and found that two new processes need to be included in order to understand the observed clustering. We then study the distribution of cold gas in dark matter haloes central to the processes of galaxy formation. We present the cold gas mass function and its evolution with redshift. We have found that the clustering predicted by the semi-analytic models agrees well with the HIPASS measurements of Meyer et al. (2007). We have calculated effective volume for redshift surveys planned with Square Kilometre Array (SKA) and compared with that of the optical Euclid mission. Finally, we study the clustering of faint extragalactic sources which are one of the foregrounds in PLANCK maps. We predict the clustering of faint extragalactic sources using a hybrid GRASIL+GALFORM+N-body model. We have compared the hybrid scheme with analytic clustering estimates. On large scales the two approaches agree, but for multipoles with l>500 the results differ significantly, with the hybrid approach being the more accurate.