Star Formation In The Cluster Merger DLSCL J0916.2+2953
  We investigate star formation in DLSCL J0916.2+2953, a dissociative merger of
two clusters at z=0.53 that has progressed $1.1^{+1.3}_{-0.4}$ Gyr since first
pass-through. We attempt to reveal the effects a collision may have had on the
evolution of the cluster galaxies by tracing their star formation history. We
probe current and recent activity to identify a possible star formation event
at the time of the merger using EW(Hd), EW([OII]), and D$_{n}$4000 measured
from the composite spectra of 64 cluster and 153 coeval field galaxies. We
supplement $Keck$ DEIMOS spectra with DLS and $HST$ imaging to determine the
color, stellar mass, and morphology of each galaxy and conduct a comprehensive
study of the populations in this complex structure. Spectral results indicate
the average cluster and cluster red sequence galaxies experienced no enhanced
star formation relative to the surrounding field during the merger, ruling out
a predominantly merger-quenched population. We find that the average blue
galaxy in the North cluster is currently active and in the South cluster is
currently post-starburst having undergone a recent star formation event. While
the North activity could be latent or long-term merger effects, a young blue
stellar population and irregular geometry suggest the cluster was still forming
prior the collision. While the South activity coincides with the time of the
merger, the blue early-type population could be a result of secular cluster
processes. The evidence suggests that the dearth or surfeit of activity is
indiscernible from normal cluster galaxy evolution.
