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J. Annis, S. Kent (Fermilab), F. Castander, D. Eisenstein (U. Chicago), J. Gunn, R. Kim, R. Lupton (Princeton U.), R. Nichol (Carnegie Mellon U.), M. Postman (STScI), W. Voges (MPI Garching), SDSS Collaboration
We present a new technique for finding galaxy clusters based on looking for a core of red, early type galaxies in the cluster center. These galaxies are known to have a small dispersion in color out to at least z=0.5. Further, the brightest of the ellipticals have near constant luminosity. In the maxBCG technique, one looks for objects whose appararent magnitudes and colors are consistent with their being brightest cluster galaxies (BCGs). If one presumes that any such object is a BCG, one can estimate a redshift and then search an area a half megaparsec around the galaxy for other galaxies that have the colors of the E/S0 ridgeline. One obtains a good estimate of the redshift by jointly minimizing the difference from the mean restframe brightest cluster galaxy properties while maximizing the number of galaxies in the E/S0 ridgeline. We have run this algoritm on the Abell clusters in the Sloan Digital Sky Survey commisioning data area with known redshifts, and find that the error in the estimated redshift z is only 0.02.
This work was supported by the U.S. Department of Energy under contract No. DE-AC02-76CH03000.