Physics & Astronomy Colloquium

Speaker: Xinyu Dai  (University of Oklahoma)

Title: An Extragalactic Journey with Active Galactic Nuclei, Gravitational Lenses, Galaxy Clusters, and Cosmic Voids

Abstract: I will present my research on several areas of extragalactic astronomy. Galaxy clusters are the largest gravitationally bound objects and are sensitive probes for structure formation and cosmology. The Swift AGN and Cluster Survey (SACS) has the survey depth and area approaching the planned eROSITA deep survey. The final catalog will contain 2000 X-ray selected clusters, where half of them will be z>0.5 clusters. This will significantly increase the number of X-ray clusters selected in this range, and allow us to place much tighter constraints on cluster evolution, such as the evolution of baryon fraction across cosmic time. Spatially resolving the different components in AGN central engines will transform the studies of physics around supermassive black holes to an unprecedented new regime. Gravitationally microlensed quasars provides a novel tool, with equivalent angular resolutions of nano-arcsecs, to resolve AGN central engines that cannot be directly imaged from current nor future instruments. I will present our current constraints on the UV disk and X-ray corona, which has challenged and re-defined models for these emission components, and the spin of supermassive black holes. Finally, I will discuss the constraints on the microlens population in the lensing galaxy.