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Date and Time of the Query: 2019-04-23 T11:19:29 PDT
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For refcode 2003ApJ...585..215Y:
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Copyright by American Astronomical Society. Reproduced by permission
2003ApJ...585..215Y Correlations of Richness and Global Properties in Galaxy Clusters H. K. C. Yee and E. Ellingson Received 2002 July 1; accepted 2002 November 4 ABSTRACT Richness is a key defining characteristic of a galaxy cluster. We measure the optical richness of galaxy clusters from the Canadian Network for Observational Cosmology Cluster Redshift Survey using the galaxy cluster center correlation amplitude B_gc_. We show that the B_gc_ values measured using photometric catalogs are consistent with those derived from redshift catalogs, indicating that richness can be measured reliably from photometric data alone, even at moderate redshifts of ~0.6. We establish the correlations between optical richness and other important attributes of a galaxy cluster, such as velocity dispersion, mass, radius, and X-ray temperature and luminosity. We find that the scaling relations of these quantities with richness are entirely consistent with those derived by assuming a simple mass density profile at 0.5 h_50_^-1^ Mpc of {rho} ~ r- 1.8. The excellent correlations between B_gc_ and velocity dispersion and X-ray temperature allow one to use richness, an easily measurable quantity using relatively shallow optical imaging data alone, as a predictor of these quantities at moderate redshifts. The B_gc_ parameter can be used to estimate the velocity dispersion of a cluster to a precision of approximately 15% (~+/-100 km s^-1^) and X-ray temperature to about 20%. Similar correlations, but with larger scatter, are also obtained between richness and the characteristic radius and mass of the clusters. We compare the relative merits of B_gc_, T_X_, and L_X_ as predictors of the dynamical mass and find that they are comparable, providing estimates at an accuracy of ~30%. We also perform similar analyses of correlations between richness and velocity dispersion, T_X_, and L_X_ with a sample of low-redshift Abell clusters and find consistent results, but with larger scatter, which may be the result of a less homogeneous database or sample-dependent effects. Subject headings: galaxies: clusters: general - galaxies: evolution - galaxies: high-redshift
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