GCF2021_talk_strazzullo

We present results from recent and ongoing investigations of galaxy populations in the central regions of a sample of five massive galaxy clusters at z~1.5 identified in the South Pole Telescope Sunyaev-Zel’dovich (SPT-SZ) survey. With a mass threshold of ~4 10^14 M⊙ and an area of 2500 square degrees, at z~1.5 SPT-SZ identifies the rarest, most massive clusters that first emerge from the cosmic web, unique structures where to study early environmental effects on the evolution of galaxies, at a cosmic time bridging active proto-cluster environments at z≳2 and largely quiescent z≲1 cluster cores. In the context of the many recent studies of galaxy populations in distant clusters, we present results focusing on environmental quenching and structural evolution. Albeit with some potentially significant variation, we find typically enhanced quiescent fractions with environmental quenching efficiencies of ~50-80%, suggesting that massive cluster core environments at z~1.5 are already efficient at suppressing star formation. The population of bulge-dominated galaxies is overall also enhanced with respect to the field (morphology-density relation), but the broad structural properties of quiescent and star-forming populations (separately) in the cluster cores are remarkably similar to those of field counterparts. These observations highlight the interplay between star formation suppression and structural evolution in early cluster environments, constraining processes and timescales.