1994/09/07 by James J. Frederic · 7 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Galaxies: Formation, Evolution, Phenomena #Scientific Research and Discoveries #astro-ph
paper · pdf · doi:10.1086/192142
27 pages + 15 figures, AASTeX, ApJS accepted. Compressed postscript figures available in ftp://arcturus.mit.edu/Preprints/grps1_figs.tar. CSR-94-20
arxiv created 1994/09/07 · openalex publication_date 1995/04/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
Using simulated redshift surveys generated from a high-resolution N- body cosmological structure simulation, we study algorithms used to identify groups of galaxies in redshift space. Two algorithms are investigated; both are friends-of-friends schemes with variable linking lengths in the radial and transverse dimensions. The chief difference between the algorithms is in the redshift linking length. The algorithm proposed by Huchra & Geller (1982) uses a generous linking length designed to find "fingers of god," while that of Nolthenius & White (1987) uses a smaller linking length to minimize contamination by projection. We find that neither of the algorithms studied is intrinsically superior to the other; rather, the ideal algorithm as well as the ideal algorithm parameters depends on the purpose for which groups are to be studied. The Huchra & Geller algorithm misses few real groups, at the cost of including some spurious groups and members, while the Nolthenius & White algorithm misses high velocity dispersion groups and members but is less likely to include interlopers in its group assignments. Adjusting the parameters of either algorithm results in a trade-off between group accuracy and completeness. In a companion paper we investigate the accuracy of virial mass estimates and clustering properties of groups identified using these algorithms.