The purpose of this project is to observe clusters of galaxies using the Sunyaev-Zeldovich (SZ) effect, which is the diminution of the Cosmic Microwave Background radiation as it passes through hot cluster gas. The project will use the MUSTANG bolometer camera on the Green Bank Telescope (GBT) to make high sensitivity cluster maps at 90 GHz with 9 arcsecond resolution, the highest ever for SZ measurements. It will exploit this high resolution and sensitivity to search for shocks, for evidence of helium sedimentation, and to compare mass estimates from SZ scaling relations to those based on weak lensing data. It will also carry out a finder survey for the high-redshift tail of millimeter-wave galaxies for ALMA follow-up.
Broader impacts of the work include training of undergraduate and graduate students, developing high frequency capability for the GBT, and providing continued access to MUSTANG for the general astronomical community.
Clusters of galaxies -- the largest gravitationally-bound objects in the Universe -- provide important tests of cosmology and serve as rich astrophysical laboratories for events such as mergers and AGN outbursts, the two most energetic events to happen since the Big Bang. As tracers of the evolution of structure, clusters of galaxies represent an important cosmological tool being exploited by a host of current and future projects such as Planck, the South Pole Telescope, the Atacama Cosmology Telescope, LSST, Euclid, and eROSITA. However, the mass scaling relationship used to extract cosmological parameters relies heavily on X-ray measurements, which are biased towards the high density regions of clusters. Maps of the Sunyaev-Zel'dovich effect in galaxy clusters at 90~GHz with the 100-meter Green Bank Telescope (GBT) provide the resolution needed to probe these objects. Our research, utilizing the MUSTANG instrument on the GBT, has produced tantalizing results at 90~GHz. With several hundred hours of observing time, we have made high resolution the maps of the inner regions of clusters of galaxies. These maps have allowed us to study shocks and other energetic events that propagate through the clusters after the violent mergers which serve to make them grow even more massive. Perhaps the most important outcome of this research is the realization that these high-resolution measurements can be made at all. Having proven the technique and developed the software tools, we are now in a position to utilize more sophisticated instrumentation to make many bigger and deeper maps. With hundreds of cluster observations planned over the coming years, we will have a large enough statistical sample to not only study the cluster physics, but possibly help to constrain the cosmological parameters derived from large-scale cluster surveys.
