Affiliation:
1. Department of Physics, Lancaster University , Lancaster LA1 4YB, UK
Abstract
ABSTRACT
We introduce AutoEnRichness, a hybrid approach that combines empirical and analytical strategies to determine the richness of galaxy clusters (in the redshift range of 0.1 ≤ z ≤ 0.35) using photometry data from the Sloan Digital Sky Survey Data Release 16, where cluster richness can be used as a proxy for cluster mass. In order to reliably estimate cluster richness, it is vital that the background subtraction is as accurate as possible when distinguishing cluster and field galaxies to mitigate severe contamination. AutoEnRichness is comprised of a multistage machine learning algorithm that performs background subtraction of interloping field galaxies along the cluster line of sight and a conventional luminosity distribution fitting approach that estimates cluster richness based only on the number of galaxies within a magnitude range and search area. In this proof-of-concept study, we obtain a balanced accuracy of 83.20 per cent when distinguishing between cluster and field galaxies as well as a median absolute percentage error of 33.50 per cent between our estimated cluster richnesses and known cluster richnesses within r200. In the future, we aim for AutoEnRichness to be applied on upcoming large-scale optical surveys, such as the Legacy Survey of Space and Time and Euclid, to estimate the richness of a large sample of galaxy groups and clusters from across the halo mass function. This would advance our overall understanding of galaxy evolution within overdense environments as well as enable cosmological parameters to be further constrained.
Funder
Science and Technology Facilities Council
University of Oregon
University of California, Los Angeles
Alfred P. Sloan Foundation
U.S. Department of Energy
Office of Science
University of Utah
Carnegie Mellon University
Johns Hopkins University
University of Tokyo
Lawrence Berkeley National Laboratory
Leibniz-Institut für Astrophysik Potsdam
New Mexico State University
New York University
University of Notre Dame
MCTI
Ohio State University
Pennsylvania State University
Universidad Nacional Autónoma de México
University of Arizona
University of Colorado Boulder
Oxford University
University of Portsmouth
University of Virginia
University of Washington
Vanderbilt University
Yale University
Publisher
Oxford University Press (OUP)
Subject
Space and Planetary Science,Astronomy and Astrophysics