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K. Rines (Yale/YCAA), A. Diaferio (U. Torino)
We use the Fourth Data Release of the Sloan Digital Sky Survey to test the ubiquity of infall patterns around galaxy clusters. The CAIRNS project found infall patterns in all 9 clusters in the survey, but the cluster sample was incomplete. Matching X-ray cluster catalogs with SDSS, we search for infall patterns in a complete sample of X-ray selected clusters. Very clean infall patterns are apparent in most of the clusters, with the fraction decreasing with increasing redshift due to shallower sampling. Over 90% of clusters in a well-defined sample limited by redshift (ensuring good sampling) and X-ray flux (excluding superpositions) show clean infall patterns. Similar to CAIRNS, cluster infall patterns are better defined in observations than in simulations. Further work is needed to determine whether this difference lies in the galaxy formation recipes used in simulations or is more fundamental. We use the infall patterns to compute mass profiles for the clusters and compare them to model profiles. We confirm the conclusion of CAIRNS that cluster infall regions are well fit by NFW and Hernquist profiles and poorly fit by singular isothermal spheres.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.