The CluMPR Galaxy Cluster-Finding Algorithm and DESI Legacy Survey Galaxy Cluster Catalogue

TL;DR

This paper introduces CluMPR, a new galaxy cluster-finding algorithm utilizing photometric redshifts and stellar mass data, applied to the DESI Legacy Survey to create a large catalog of high-redshift clusters for cosmology and astrophysics research.

Contribution

The paper presents CluMPR, a novel cluster detection method that improves high-redshift cluster identification using probabilistic membership and mass measurements, applied to a large survey.

Findings

Created a catalog of ~300,000 galaxy cluster candidates up to z=1.

CluMPR effectively identifies high-redshift clusters with minimal contamination.

Discovered candidate strongly-lensed quasars, including known systems.

Abstract

Galaxy clusters enable unique opportunities to study cosmology, dark matter, galaxy evolution, and strongly-lensed transients. We here present a new cluster-finding algorithm, CluMPR (Clusters from Masses and Photometric Redshifts), that exploits photometric redshifts (photo-z's) as well as photometric stellar mass measurements. CluMPR uses a 2-dimensional binary search tree to search for overdensities of massive galaxies with similar redshifts on the sky and then probabilistically assigns cluster membership by accounting for photo-z uncertainties. We leverage the deep DESI Legacy Survey grzW1W2 imaging over one-third of the sky to create a catalogue of ~ 300,000 galaxy cluster candidates out to z = 1, including tabulations of member galaxies and estimates of each cluster's total stellar mass. Compared to other methods, CluMPR is particularly effective at identifying clusters at the high end of the redshift range considered (z = 0.75-1), with minimal contamination from low-mass groups. These characteristics make it ideal for identifying strongly lensed high-redshift supernovae and quasars that are powerful probes of cosmology, dark matter, and stellar astrophysics. As an example application of this cluster catalogue, we present a catalogue of candidate wide-angle strongly-lensed quasars in Appendix C. The five best candidates identified from this sample include two known lensed quasar systems and a possible changing-look lensed QSO with SDSS spectroscopy. All code and catalogues produced in this work are publicly available (see Data Availability).