A Planck-selected dusty proto-cluster at z = 2.16 associated with a strong overdensity of massive Hα-emitting galaxies

We have discovered an overdensity of Hα-emitting galaxies associated with a Planck compact source in the COSMOS field (PHz G237.0+42.5) through narrow-band imaging observations with the Subaru Multi-Object InfraRed Camera and Spectrograph (MOIRCS). This Planck-selected dusty proto-cluster at z = 2.16 has 38 Hα emitters including six spectroscopically confirmed galaxies in the observed MOIRCS 4 × 7 arcmin2 field (corresponding to ∼2.0 × 3.5 Mpc2 in the physical scale). We find that massive Hα emitters with log (M/M) >10.5 are strongly clustered in the core of the proto-cluster (within ∼300 kpc from the density peak of the Hα emitters). Most of the Hα emitters in this proto-cluster lie along the star-forming main sequence using Hα-based estimates of the star formation rate (SFR). Meanwhile, the cluster total SFRs derived by integrating the Hα-based SFRs is an order of magnitude smaller than those estimated from Planck/Herschel far-infrared photometry. Our results suggest that Hα is a good observable for detecting moderately star-forming galaxies and for tracing the large-scale environment in and around high-redshift dusty proto-clusters. However, there is a possibility that a large fraction of star formation could be obscured by dust and undetected in Hα observations. © 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu