Sharpening our view of Cluster Cosmology

Clusters of galaxies are excellent tracers of the matter distribution in the Universe. Significant resources have been put into compiling cluster catalogs, because such surveys can be used to derive important cosmological parameters. One survey technique is to use the Sunyaev-Zel'dovich effect (SZE), which is when hot gas inside galaxy clusters distorts the spectrum of light from the Big Bang. However, radio emission from individual galaxies and cluster mergers can complicate interpretation of the SZE, resulting in sources of bias in cosmological parameters derived from cluster catalogs. High resolution images taken at radio frequencies can be used to quantify these biases. The investigators will use the MUSTANG2 camera on the Green Bank Telescope (GBT) to map clusters. Results from this program will help produce more accurate results from investments in past, current, and future galaxy cluster surveys. During this work, the investigators will maintain MUSTANG2, ensuring it remains available to the wider astronomical community. To help train a more diverse next generation of STEM workers, the team will work with the Simons Foundation and the Society of Black Physicists to host students working on MUSTANG2 projects. Outreach to middle school students is planned by participation in the Girls Exploring The Universe (GETU) summer camp run by the University of Virginia. In addition, the PI will continue public outreach activities in the Philadelphia area. The large scatter in cluster masses between the overlapping ACT (Atacama Cosmology Telescope) and eROSITA surveys will be investigated first. The team will (1) Finish a blind survey of clusters for compact sources at SZE frequencies (2) Use the results to correct the masses of the observed sample (3) Build a model for how likely sources are in different types of clusters that can be used to correct the mass-SZE relationship in a statistical sense and (4) Use deeper observations of selected clusters with remaining discrepant masses between surveys to find the cause. As part of the maintenance of MUSTANG2, the team will better integrate the pipeline into the observatory software infrastructure, further facilitating the use of MUSTANG2 data by the astronomical community. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.