MUSTANG HIGH ANGULAR RESOLUTION SUNYAEV-ZEL'DOVICH EFFECT IMAGING OF SUBSTRUCTURE IN FOUR GALAXY CLUSTERS

We present resolved images of four massive clusters of galaxies through the Sunyaev-Zel'dovich effect (SZE). These measurements, made at 90 GHz with the MUSTANG receiver on the Green Bank Telescope (GBT), reveal pressure substructure to the intracluster medium (ICM) in three of the four systems. The SZE and X-ray morphology of MACS0744.8+3927 are suggestive of the presence of a weak shock outside the cluster core. By fitting the Rankine-Hugoniot density jump conditions in a complementary SZE/X-ray analysis, we asses the feasibility of this interpretation. We conclude that a weak shock with a Mach number of M = 1.2(-0.2)(+0.2) and a shock velocity of 1827(-195)(+267) km s(-1) adequately describes the observed phenomenology. Deeper Chandra data are needed for confirmation. In RXJ1347.5-1145, we present a new reduction of previously reported data and confirm the presence of a southeast SZE enhancement with a significance of 13.9 sigma when smoothed to 18 '' resolution. This too is likely caused by shock-heated gas produced in a recent merger. In our highest redshift system, CL1226.9+3332, we detect substructure at a peak significance of 4.6 sigma in the form of a ridge oriented orthogonally to the vector connecting the main mass peak and a subclump revealed by weak lensing. We also conclude that the gas distribution is elongated in a southwest direction, consistent with a previously proposed merger scenario. The SZE image of the cool core cluster A1835 is, in contrast, consistent with azimuthally symmetric signal only. This pilot study demonstrates the potential of high-resolution SZE images to complement X-ray data and probe the dynamics of galaxy clusters.