paper

An Extended Halo-based Group/Cluster finder: application to the DESI legacy imaging surveys DR8

arXiv:2012.14998 · doi:10.3847/1538-4357/abddb2

Abstract

We extend the halo-based group finder developed by \citet[][]{Yang2005a} to use data {\it simultaneously} with either photometric or spectroscopic redshifts. A mock galaxy redshift survey constructed from a high-resolution N-body simulation is used to evaluate the performance of this extended group finder. For galaxies with magnitude and redshift in the DESI legacy imaging surveys (the Legacy Surveys), our group finder successfully identifies more than 60\% of the members in about of halos with mass $\ga 10^{12.5}\msunh$. Detected groups with mass $\ga 10^{12.0}\msunh$ have a purity (the fraction of true groups) greater than 90\%. The halo mass assigned to each group has an uncertainty of about 0.2 dex at the high mass end $\ga 10^{13.5}\msunh$ and 0.40 dex at the low mass end. Groups with more than 10 members have a redshift accuracy of . We apply this group finder to the Legacy Surveys DR8 and find 5.2 Million groups with at least 3 members. About 387,000 of these groups have at least 10 members. The resulting catalog containing 3D coordinates, richness, halo masses, and total group luminosities, is made publicly available.

Due to a bug in our code, our calculation of the completeness and interloper fraction of the group members was not correct, which resulted in our choice of a low background B=2.5. In this new version of the paper, we updated results with the theoretical fiducial background B=10. Most of the changes in the figures are virtually too small to notice. This version supersedes the one published in ApJ

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