Tidal Interactions and Mergers in Intermediate Redshift EDisCS Clusters
  We study the fraction of tidal interactions and mergers with well identified
observability timescales ($f_{\rm TIM}$) in group, cluster, and accompanying
field galaxies and its dependence on redshift ($z$), cluster velocity
dispersion ($\sigma$) and environment analyzing HST-ACS images and catalogs
from the ESO Distant Cluster Survey (EDisCS). Our sample consists of 11
clusters, 7 groups, and accompanying field galaxies at $0.4 \leq z \leq 0.8$.
We derive $f_{\rm TIM}$ using both a visual classification of galaxy
morphologies and an automated method, the $G-M_{20}$ method. We calibrate this
method using the visual classifications that were performed on a subset of our
sample. We find marginal evidence for a trend between $f_{\rm TIM}$ and $z$, in
that higher $z$ values correspond to higher $f_{\rm TIM}$. However, we also
cannot rule out the null hypothesis of no correlation at higher than 68%
confidence. No trend is present between $f_{\rm TIM}$ and $\sigma$. We find
that $f_{\rm TIM}$ shows suggestive peaks in groups, and tentatively in
clusters at $R > 0.5\times R_{200}$, implying that $f_{\rm TIM}$ gets boosted
in these intermediate density environments. However, our analysis of the local
densities of our cluster sample does not reveal a trend between $f_{\rm TIM}$
and density, except for a potential enhancement at the very highest densities.
We also perform an analysis of projected radius-velocity phase space for our
cluster members. Our results reveal that tidal interactions and mergers (TIM),
and undisturbed galaxies only have a 6% probability of having been drawn from
the same parent population in their velocity distribution and 37% in radii, in
agreement with the modest differences obtained in $f_{\rm TIM}$ at the
clusters.
