Jellyfish: Evidence of extreme ram-pressure stripping in massive galaxy
  clusters
  Ram-pressure stripping by the gaseous intra-cluster medium has been proposed
as the dominant physical mechanism driving the rapid evolution of galaxies in
dense environments. Detailed studies of this process have, however, largely
been limited to relatively modest examples affecting only the outermost gas
layers of galaxies in nearby and/or low-mass galaxy clusters. We here present
results from our search for extreme cases of gas-galaxy interactions in much
more massive, X-ray selected clusters at $z>0.3$. Using Hubble Space Telescope
snapshots in the F606W and F814W passbands, we have discovered dramatic
evidence of ram-pressure stripping in which copious amounts of gas are first
shock compressed and then removed from galaxies falling into the cluster.
Vigorous starbursts triggered by this process across the galaxy-gas interface
and in the debris trail cause these galaxies to temporarily become some of the
brightest cluster members in the F606W passband, capable of outshining even the
Brightest Cluster Galaxy. Based on the spatial distribution and orientation of
systems viewed nearly edge-on in our survey, we speculate that infall at large
impact parameter gives rise to particularly long-lasting stripping events. Our
sample of six spectacular examples identified in clusters from the Massive
Cluster Survey, all featuring $M_{\rm F606W}<-$21 mag, doubles the number of
such systems presently known at $z>0.2$ and facilitates detailed quantitative
studies of the most violent galaxy evolution in clusters.
