The Stellar Mass Components of Galaxies: Comparing Semi-Analytical
  Models with Observation
  We compare the stellar masses of central and satellite galaxies predicted by
three independent semianalytical models with observational results obtained
from a large galaxy group catalogue constructed from the Sloan Digital Sky
Survey. In particular, we compare the stellar mass functions of centrals and
satellites, the relation between total stellar mass and halo mass, and the
conditional stellar mass functions, which specify the average number of
galaxies of stellar mass M_* that reside in a halo of mass M_h. The
semi-analytical models only predict the correct stellar masses of central
galaxies within a limited mass range and all models fail to reproduce the sharp
decline of stellar mass with decreasing halo mass observed at the low mass end.
In addition, all models over-predict the number of satellite galaxies by
roughly a factor of two. The predicted stellar mass in satellite galaxies can
be made to match the data by assuming that a significant fraction of satellite
galaxies are tidally stripped and disrupted, giving rise to a population of
intra-cluster stars in their host halos. However, the amount of intra-cluster
stars thus predicted is too large compared to observation. This suggests that
current galaxy formation models still have serious problems in modeling star
formation in low-mass halos.
