From Panoramic to Microscopic: Probing the Nature of Cluster Galaxy Population across Cosmic Time with Subaru

Yusei Koyama

We present the results from our panoramic H-alpha observations of distant galaxy clusters (at 0.4<z<2.2) with Subaru over the last ~5-years with "MAHALO-Subaru" campaign. Taking advantage of the wide-field capabilities of the Subaru instruments, our survey covers a wide environmental range from cluster core to surrounding structures (over ~10Mpc) at all redshifts. Our survey revealed that the correlation between stellar mass and SFR (star-forming "main sequence") does not change with environment. We also identified a large number of H-alpha emitters with optically red colours. Those "red star-forming galaxies (RSFG)" tend to be IR-luminous, massive, dusty star-forming galaxies based on the panoramic IR-submm observations (with AKARI, Spitzer, and SCUBA-2/JCMT). Importantly, the environment of RSFGs changes throughout the cosmic time in "inside-out" fashion: they are most prevalent in proto-cluster core at z~2, while they are preferentially located in the cluster outskirts or surrounding groups at z<1. Our follow-up 3-D (IFU) spectroscopy with GMOS/Gemini and KMOS/VLT revealed that most of RSFGs show disk kinematics (and flat metallicity gradients), suggesting they are not necessarily triggered by major merger events. We also present our new "GANBA-Subaru" project (Galaxy Anatomy with Narrow-Band AO-imaging with Subaru), where we exploit Subaru IRCS+AO188 to spatially resolve the H-alpha emission within those key population by AO-assisted narrow-band (H-alpha) imaging. Our preliminary analyses demonstrate that H-alpha emission is more extended than the stellar continuum light, and the H-alpha "clumps" identified inside the galaxies tend to be younger than the core, suggesting "inside-out" mass assembly. In my presentation, I will attempt to bridge the panoramic views (from MAHALO-Subaru) and microscopic views (from GANBA-Subaru and IFU observations) of cluster galaxy evolution over the "noon" and "afternoon" epoch of galaxy formation.