The Zurich Environmental Study (ZENS) of Galaxies in Groups along the
  Cosmic Web. V. Properties and Frequency of Merging Satellites and Centrals in
  Different Environments
  We use the Zurich ENvironmental Study (ZENS) database to investigate the
environmental dependence of the merger fraction $\Gamma$ and merging galaxy
properties in a sample of ~1300 group galaxies with $M>10^{9.2}M_\odot$ and
0.05<z<0.0585. In all galaxy mass bins investigated in our study, we find that
$\Gamma$ decreases by a factor of ~2-3 in groups with halo masses
$M_{HALO}>10^{13.5} M_\odot$ relative to less massive systems, indicating a
suppression of merger activity in large potential wells. In the fiducial case
of relaxed groups only, we measure a variation $\Delta\Gamma/\Delta \log
(M_{HALO}) \sim - 0.07$ dex$^{-1}$, which is almost independent of galaxy mass
and merger stage. At galaxy masses $>10^{10.2} M_\odot$, most mergers are dry
accretions of quenched satellites onto quenched centrals, leading to a strong
increase of $\Gamma$ with decreasing group-centric distance at these mass
scales.Both satellite and central galaxies in these high mass mergers do not
differ in color and structural properties from a control sample of nonmerging
galaxies of equal mass and rank. At galaxy masses $<10^{10.2} M_\odot$, where
we mostly probe satellite-satellite pairs and mergers between star-forming
systems, close pairs (projected distance $<10-20$ kpc) show instead
$\sim2\times$ enhanced (specific) star formation rates and $\sim1.5\times$
larger sizes than similar mass, nonmerging satellites. The increase in both
size and SFR leads to similar surface star-formation densities in the merging
and control-sample satellite populations.
