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P.A.A. Lopes (CIT), R.R. de Carvalho (ON), R.R. Gal (JHU), S.G. Djorgovski (CIT), S.C. Odewahn (ASU), A.A. Mahabal, R. Brunner, J. Bird (CIT), DPOSS Team
We present a large cluster catalog from DPOSS at intermediate redshifts (0.3 < z < 0.6). We use the faint end data (r > 19) available from DPOSS to generate a list of rich cluster candidates in the highest quality DPOSS fields with galactic latitude |b| > 40\circ. We look for overdensities on the projected distribution of objects in the sky, which are interpreted as cluster candidates. We generate a list of rich cluster candidates, which we expect to be complete to z ~ 0.5, at least. This work is an extension of Gal (2001, Ph.D. Thesis Caltech) which could cover a large contiguous area, but was limited in magnitude due to photometry and object classification accuracy. Here we exploit DPOSS data to its limits, which is equivalent to ~2.0 magnitudes deeper. However, due to the significant selection effects imposed by plate dependent depth effects we limit ourselves to the highest grade plates (~2000 square degress). We also ignore classification for objects with r > 20. We assume the stellar contamination is low for these high galactic fields and the stellar distribution can be considered as an uniform background.
Two different methods are employed for the cluster search on this data set. The first makes use of an Adaptive Kernel technique (Gal et al. 2000, Apj, 236, 351), while the second is based on a Voronoi tesselation code (Ramella et al. 2001, A&A, 368, 776). We cross-correlate both catalogs to generate a common list of cluster candidates.
This intermediate-redshift cluster catalog should be useful for a variety of follow-up studies. Currently, we have a folow-up imaging of some candidates being taken at the Palomar 60'' telescope.
Cataloging of DPOSS was supported in part by a generous gift from the Norris Foundation. Software development work was supported in part by grants from NASA. P. Lopes acknowledges a fellowship from CNPq/Brazil. J. Bird acknowledges a SURF fellowship.