MCC members hauled in a major amount of JVLA radio observation time in the 2014B semester to study the radio emission of merging clusters. One proposal, led by Will Dawson, will obtain deep (30 total hours) polarization measurements of 5 double radio relic clusters (A1240, MACS J1752.0+4440, RXC J1314.4-2515, ZwCL 0008.8+5215, and ZwCL 2341.1+0000). These observations will enable us to improve dark matter cross-section constraints by almost an order of magnitude! The second proposal, led by Reinout van Weeren, will obtain very deep radio observations (64 hours total) of four of the the Frontier Field clusters (MACS J0717, MACS J1149, MACS J0416, and A2744).
Major Radio Wins for Merging Clusters
MCC member Marcus Bruggen and others have shown how the star formation rate (SFR) in cluster spiral galaxies can be enhanced due to major cluster merger induced shocks of the intra-cluster-medium (Roedigner et al. 2014). They find that local enhancements in the SFR of about a factor of 4 and global SFR enhancements of a factor of ~1.5, but that these enhancements are limited to a short duration of ~15 Myr following the passage of the shock (typical timescales of cluster mergers are about 1 Gyr). Thus enhanced SFR might be expected to be limited to occurring within galaxies that are a few 100 kpc behind the progressing shock. MCC can test this hypothesis using our extensive Keck galaxy spectra, X-ray & radio observations of the shock, and dynamics analysis.
Roediger, E. et al., 2014. Star formation in shocked cluster spirals and their tails. eprint arXiv:1405.1033.
A video by Elke Roediger showing how the projected gas density of a spiral galaxy is affected by a passing intra-cluster-medium shock, common in major cluster mergers. Star formation is more likely in regions with denser gas. See more of Elke's simulation videos at: http://www.hs.uni-hamburg.de/DE/Ins/Per/Roediger/research.html#Spiral.