The nature of H α-selected galaxies along the large-scale structure at z = 0.4 revealed by Subaru Hyper Suprime-Cam survey

Abstract

We present the environmental dependence of color, stellar mass, and star formation (SF) activity in Hα-selected galaxies along the large-scale structure at z = 0.4 hosting twin clusters in the DEEP2-3 field, discovered by the Subaru Strategic Program of Hyper Suprime- Cam (HSC SSP). By combining photo-z-selected galaxies and Hα emitters selected with broadband and narrowband (NB) data from the recent data release of HSC SSP (DR1), we confirm that galaxies in higher-density environments or galaxies in cluster central regions show redder colors. We find that there still remains a possible color-density and color- radius correlation even if we restrict the sample to Hα-selected galaxies, probably due to the presence of massive Hα emitters in denser regions. We also find a hint of increased star formation rates (SFR) amongst Hα emitters toward the highest-density environment, again primarily driven by the excess of red/massive Hα emitters in high-density environments, while their specific SFRs do not significantly change with environment. This work demonstrates the power of the HSC SSP NB data for studying SF galaxies across environments in the distant universe.