Observational Cosmology Seminar

Galaxy clusters are powerful probes of both cosmology and astrophysics, tracing the growth of large-scale structure while providing a laboratory for studying the physics of the intracluster medium (ICM) and feedback from Active Galactic Nuclei (AGN). In this prep candidacy talk, I will present the planned research program for my thesis, which uses multi-wavelength observations and simulations to characterize key astrophysics that affect cluster-based cosmological measurements. I will discuss how millimeter emission from cluster-member AGNs contaminates Sunyaev-Zel'dovich (SZ) cluster surveys, including our recovery of two clusters in ACT maps using CARMA data whose SZ signals were obscured by central AGN emission. Building on this work, I will present plans for upcoming scheduled ATCA observations of millimeter-bright AGNs in the SPT-Deep field, which will provide the first observational constraints on AGN-induced biases in a complete SZ-selected cluster sample. I will also present studies of cluster triaxiality and its impact on survey selection and weak-lensing mass calibration. We show that SZ selection preferentially detects clusters elongated along the line of sight, leading to biases in weak-lensing mass estimates. To quantify the effect of triaxiality, our group is developing a multi-probe framework that combines X-ray, SZ, and weak-lensing observations of the CHEX-MATE cluster sample to constrain cluster geometry, improve mass measurements, and probe dark matter physics and mass accretion histories. In addition, I will discuss ongoing work on cluster scaling relations using both CHEX-MATE observations and The300 simulation suite, with the goals of identifying low-scatter mass proxies and quantifying correlations between cluster observables. Finally, I will present our work characterizing non-thermal pressure support in the ICM of Abell 3266 through combined SZ and X-ray fluctuation measurements, representing the first such analysis using eROSITA data.