A <i>Planck</i>-selected dusty proto-cluster at <i>z</i> = 2.16 associated with a strong overdensity of massive H?-emitting galaxies

We discovered an over-density of H-alpha-emitting galaxies associated with a Planck compact source in the COSMOS field (PHzG237.0+42.5) through narrow-band imaging observations Subaru/MOIRCS. This Planck-selected dusty proto-cluster at z=2.16 has 38 H-alpha emitters including six spectroscopically confirmed observed MOIRCS 4'x7' (corresponding to ~2.0x3.5~Mpc^2 physical scale). find that massive log(M*/Msun)>10.5 are strongly clustered core (within ~300-kpc from density peak emitters). Most this lie along star-forming main sequence using H-alpha-based SFR estimates, whilst cluster total derived by integrating SFRs is order magnitude smaller than those estimated Planck/Herschel FIR photometry. Our results suggest good observable for detecting moderately and tracing large-scale environment around high-z proto-clusters, but there possibility large fraction star formation could be obscured dust undetected observations.