TUNA Lunch Talk:

Brian Mason


A High Resolution Image of the Sunyaev-Zel'dovich Effect in RXJ1347-1145 with MUSTANG on the GBT

March 31

12:10PM, Room 230, NRAO, Edgemont Road


Rich galaxy clusters are the peaks of the cosmic density field and therefore offer a potent probe of the evolution structure. Ongoing cluster surveys with the Atacama Cosmology Telescope (ACT) and South Pole Telescope (SPT) are seeking to exploit this fact by mapping the CMB over hundreds of square degrees, identifying clusters by the spectral distortion their hot gas imposes on the CMB (the Sunyaev-Zel'dovich Effect, or SZE), and determining their abundance as a function of mass and redshift. Since the SZE is independent of redshift this is a particularly powerful measurement, creating in principle a mass-limited sample. These analyses, like most cosmological tests with clusters, depend on assumptions about the cluster geometry and the state of the cluster gas. These assumptions can be tested, and departures quantified, with high angular resolution images of the cluster gas in X-rays and the SZE. To date essentially all measurements of the SZE have been made with compact interferometers or small single dishes with beams ~1' or larger in size.

RXJ1347-1145 is the most luminous known x-ray cluster and has been the object of extensive study across the electromagnetic spectrum. Based on its smooth, regular, strongly peaked x-ray morphology, one might conclude that it is a prototypical dynamically relaxed cluster. A 150 GHz SZE map from the Nobeyama 45m telescope, however, revealed the presence of hot (>20 keV) gas to the south east of the peak of x-ray emission, suggesting a recent, violent merger event. As a pilot study for a future program of high resolution SZE observations, two 4 hour observations of RXJ1347-1145 have been conducted with MUSTANG on the GBT. These observations result in a clear detection of the SZE and the highest angular resolution image of the SZE to date. We present our preliminary findings and indicate future directions for the work.