Cluster Mass Profiles from the Hectospec Cluster Survey (HeCS)

The Hectospec Cluster Survey (HeCS) is a spectroscopic survey of a flux-limited sample of X-ray-selected galaxy clusters at 0.1<z<0.3 with MMT/Hectospec. We obtained 19,609 new redshifts in 56 clusters to measure velocity dispersions and mass profiles extending well into their infall regions. Infall regions are an important transition environment between isolated galaxies and cluster members. Infall patterns resembling those seen in low-redshift clusters are established in clusters by z=0.3. We present mass profiles of the clusters and use these to measure scaling relations between X-ray properties and galaxy dynamics. We also explore the relation between galaxy dynamics and measures of optical richness and total stellar luminosity. Understanding cluster scaling relations is critical for interpreting large surveys like SPT, eROSITA, and DES.