Megaparsec-Scale Triggers for Star Formation: Clusters and Filaments of
  Galaxies in the Horologium-Reticulum Supercluster
  Specific indications of star-formation are presented within cluster and
filament galaxies that are members of the Horologium-Reticulum supercluster
(HRS, z ~0.06). These indicators arise from multi-wavelength observations,
primarily emission lines from optical spectroscopy and faint excess from radio
continuum (1.4 GHz) photometry. HRS galaxies exhibiting current star formation
are consistent with previous studies in that the star-forming populations
organize around megaparsec-scale filament axes as well as near the cluster
core. Therefore with support from optical photometry, mechanisms for triggering
star formation in these galaxies are most likely due to merger interactions in
lower density (and lower velocity) environments and possible bursts prior to
stripping within the higher density (and higher velocity) environments.
