Photometric redshifts for galaxies in the Subaru Hyper Suprime-Cam and unWISE and a catalogue of identified clusters of galaxies

TL;DR

This paper presents a large catalog of photometric redshifts for nearly 15 million galaxies using Subaru and WISE data, identifies over 21,000 galaxy clusters including many at high redshift, and analyzes properties of brightest cluster galaxies.

Contribution

It provides a new extensive galaxy and cluster catalog with photometric redshifts and cluster properties, especially at high redshift, based on combined optical and infrared data.

Findings

Photometric redshift uncertainty is about 0.024 for z<0.7.

Identified 21,661 galaxy clusters, including 5,537 at z>1.

Brightest cluster galaxies show little evolution in stellar mass with redshift.

Abstract

We first present a catalogue of photometric redshifts for 14.68 million galaxies derived from the 7-band photometric data of Hyper Suprime-Cam Subaru Strategic Program and the Wide-field Infrared Survey Explorer using the nearest-neighbour algorithm. The redshift uncertainty is about 0.024 for galaxies of z<0.7, and steadily increases with redshift to about 0.11 at z~2. From such a large data set, we identify 21,661 clusters of galaxies, among which 5537 clusters have redshifts z>1 and 642 clusters have z>1.5, significantly enlarging the high redshift sample of galaxy clusters. Cluster richness and mass are estimated, and these clusters have an equivalent mass of M_{500} > 0.7*10^{14} Msun. We find that the stellar mass of the brightest cluster galaxies (BCGs) in each richness bin does not significantly evolve with redshift. The fraction of star-forming BCGs increases with redshift, but does not depend on cluster mass.