The First Integral Field Unit Spectroscopic View of Shocked Cluster
  Galaxies
  Galaxy clusters grow by merging with other clusters, giving rise to Mpc-wide
shock waves that travel at 1000-2500 km/s through the intra-cluster medium. To
study the effects of merger shocks on the properties of cluster galaxies, we
present the first spatially resolved spectroscopic view of 5 H$\alpha$ emitting
galaxies located in the wake of shock fronts in the low redshift (z~0.2),
massive (~2$\times10^{15}$ M$_\odot$), post-core passage merging cluster, CIZA
J2242.8+5301 (nicknamed the `Sausage'). Our Gemini/GMOS-N integral field unit
(IFU) observations, designed to capture H$\alpha$ and [NII] emission, reveal
the nebular gas distribution, kinematics and metallicities in the galaxies over
>16 kpc scales. While the galaxies show evidence for rotational support, the
flux and velocity maps have complex features like tails and gas outflows
aligned with the merger axis of the cluster. With gradients incompatible with
inside-out disk growth, the metallicity maps are consistent with sustained star
formation (SF) throughout and outside of the galactic disks. In combination
with previous results, these pilot observations provide further evidence of a
likely connection between cluster mergers and SF triggering in cluster
galaxies, a potentially fundamental discovery revealing the interaction of
galaxies with their environment.
