Radial and Local Density Dependence of Star Formation Properties in Galaxy Clusters from the Hyper Suprime-Cam Survey

Abstract

This study examines the impact of cluster environments on galaxy properties using data from the Hyper Suprime-Cam Subaru Strategic Program and an optically selected CAMIRA cluster sample. Specifically, the study analyzes the fractions of quiescent and green valley galaxies with stellar masses above 108.6 M ⊙ at z ∼ 0.2 and 109.8 M ⊙ at z ∼ 1.1, investigating their trends in radius and density. The results indicate that a slow quenching mechanism is at work, as evidenced by a radially independent specific star formation rate reduction of 0.1 dex for star-forming galaxies in a cluster environment. The study also finds that slow quenching dominates fast quenching only for low-mass galaxies (<109.2 M ⊙) near the cluster edge, based on their contributions to the quiescent fraction. After controlling for M *, z, and local overdensity, the study still finds a significant radial gradient in the quiescent fraction, indicating active ram pressure stripping in dense environments. That said, analyzing the density trend of the quiescent fraction with other fixed parameters suggests that radial and density-related quenching processes are equally crucial for low-mass cluster galaxies. The study concludes that ram pressure stripping is the primary environmental quenching mechanism for high stellar mass galaxies in clusters. By contrast, ram pressure stripping and density-related quenching processes act comparably for low-mass cluster galaxies around the center. Near the cluster boundary, starvation and harassment become the leading quenching processes for low stellar mass galaxies.