Abstract
In this talk, I describe my work to characterize stellar populations in massive galaxies at two epochs — redshifts ~0.5 and ~5. I use spectra of galaxies in South Pole Telescope galaxy clusters to address the question: on what timescales do galaxies that end up in clusters form their stars, and does the cluster sample matter when studying these properties? We use a mass-limited cluster sample across 0.3 < z < 1.5 to constrain star formation histories and formation redshifts of 900 quiescent galaxies in clusters, as a function of cluster environment and mass. This study explores mass-dependent evolution in cluster quiescent galaxies and characterises galaxy evolution across a descendent-antecedent cluster sample.
On the other ‘end’ of the redshift scale, I will share the characterization of COOL J1241+2219, a lensed galaxy at z = 5.04 that is the brightest galaxy known at z > 5 (zAB ~ 20.5). This galaxy was discovered by COOL-LAMPS — ChicagO Optically-selected strong Lenses - Located At the Margins of Public Surveys — initiated to find strongly lensed systems, consisting primarily of a team of undergraduate students. We characterize the lensed galaxy using ground-based spectrophotometric data to find an intrinsically luminous and massive star-forming galaxy. We aim to compare CJ1241 and other COOL-LAMPS discovered lensed massive galaxies at z>3 with their potential descendents — quiescent massive galaxies at lower redshifts. With anticipated multi-wavelength spectroscopic data, including from an approved JWST Cycle 1 Program (GO 2566, PI: Khullar), we will uncover mass assembly pathways in CJ1241 well into the epoch of reionization.
