Poster Presentation

Unveiling the Size Growth of Quiescent Galaxies: Environmental Effects from UV-Optical Perspectives in Clusters vs. the Field

Author(s): Angelo George (Saint Mary's University)

Presenter: Angelo George (Saint Mary's University, NS, Canada)

I present findings from our recent study (George et al., 2025, ApJ 987, 45), investigating environmental impacts on the size evolution of massive (stellar mass > 10^9.5 M_⊙) quiescent galaxies (QGs). Using CLAUDS+HSC imaging over 18.6 deg², we studied ~86,000 field and ~1,000 cluster-core QGs at redshifts 0.1 to 0.85. We measured effective radii at rest-frame 3000Å (UV) and 5000Å (optical), as UV traces younger, low-metallicity stellar populations, while optical reveals older, stable structures, providing key insights into galaxy evolution. QGs appear larger in UV than in optical, with a stronger difference in the field. Cluster QGs are consistently smaller, particularly in UV, suggesting dense environments compact galaxies. The size-mass relation shows cluster QGs grow as rapidly as field QGs over cosmic time. We attribute rapid cluster growth to accretion of larger field QGs and newly quenched, larger “newcomers.” This talk will explore how the environment drives galaxy size evolution, highlighting the roles of newcomers and minor mergers in clusters versus the field. I will discuss how UV-optical size differences reveal distinct evolutionary pathways for QGs across environments.