Galaxy environments over cosmic time: the non-evolving radial galaxy
  distributions around massive galaxies since z=1.6
  We present a statistical study of the environments of massive galaxies in
four redshift bins between z=0.04 and z=1.6, using data from the Sloan Digital
Sky Survey (SDSS) and the NEWFIRM Medium Band Survey (NMBS). We measure the
projected radial distribution of galaxies in cylinders around a constant number
density selected sample of massive galaxies and utilize a statistical
subtraction of contaminating sources. Our analysis shows that massive primary
galaxies typically live in group halos and are surrounded by 2 to 3 satellites
with masses more than one-tenth of the primary galaxy mass. The cumulative
stellar mass in these satellites roughly equals the mass of the primary galaxy
itself. We further find that the radial number density profile of galaxies
around massive primaries has not evolved significantly in either slope or
overall normalization in the past 9.5 Gyr. A simplistic interpretation of this
result can be taken as evidence for a lack of mergers in the studied groups and
as support for a static evolution model of halos containing massive primaries.
Alternatively, there exists a tight balance between mergers and accretion of
new satellites such that the overall distribution of galaxies in and around the
halo is preserved. The latter interpretation is supported by a comparison to a
semi-analytic model, which shows a similar constant average satellite
distribution over the same redshift range.
