Slow Galaxy Growth within Rapidly Growing Dark Matter Halos
  In cold dark matter cosmologies, the most massive dark matter halos undergo
rapid growth between a redshift of z=1 and z=0, corresponding to the past 7
billion years of cosmic time. There is thus an expectation that the stellar
masses of the most massive galaxies will also rapidly grow via merging over
this redshift range. While there are examples of massive merging galaxies at
low redshift, recent observations show that the stellar masses of massive
galaxies have grown by only 30% since z=1. Some of the literature claims that
the slow growth of massive galaxies is contrary to the CDM paradigm, although
this is not necessarily the case. To determine why massive galaxies are not
growing rapidly, we have modeled how galaxies populate dark matter halos. To do
this, we have measured the space density and spatial clustering of redshift z<1
galaxies in the Bootes field of the NOAO Deep Wide-Field Survey. We have then
modeled the observations using the halo occupation distribution (HOD)
formalism. We find that the stellar masses of the largest galaxies are
proportional to dark matter halo mass to the power of a third. In the most
massive dark matter halos, we also find that the stellar mass is distributed
mostly among "satellite" galaxies. As a consequence, the stellar masses of
large galaxies are expected to increase relatively slowly, even though they
reside within rapidly growing dark matter halos.
