Although a plethora of well-studied low-z galaxy clusters with well-characterized galaxy populations exist, as we observe progressively higher redshifts, the samples diminish, and it becomes challenging to identify high-z clusters/protoclusters and determine whether the underlying relations that govern low-z clusters still hold. I will present two projects probing potential tracers for high-z clusters and the characteristics of protocluster galaxies. One strategic method for identifying high-z clusters is their association with radio loud AGNs. In particular, bent radio AGNs, a unique class of radio AGNs characterized by a “C” shaped morphology, is well-known for their association with clusters. Here, we analyze new LoTSS DR2 observations of 21 bent AGNs in clusters and 15 not in clusters from the high-z Clusters Occupied by Bent Radio AGN (COBRA) survey. We see key differences in the opening angle and spectral index between the two samples, such that sources with narrower opening angles tend to be in cluster environments and find that ~65% of cluster bent AGNs have flat cores (> -0.6) compared to ~27% of non-clusters. This finding provides further evidence that these bent AGNs are in cluster environments as well as an additional tracer for future high-z cluster/protocluster work in the LOFAR2.0 era. As we enter a high-z era defined by JWST, Euclid, and 30m telescopes, we need to understand when the cluster/protocluster environment begins to impact the galaxies, in particular their morphology. Here we present HST WFC3 F160w observations of two protoclusters at z ~ 2.23 identified via the Mapping the Most Massive Overdensities Through Hydrogen Survey. We measure the Sersic index of each galaxy and probe the morphology-density relation. We find preliminary results pointing to richer environments fostering more elliptical galaxies and numerous potential galaxy-galaxy mergers, which may indicate that the elliptical galaxy populations in these systems will soon increase.
Antonino Marasco
