A New Reduction of the Blanco Cosmology Survey: An Optically Selected Galaxy Cluster Catalog and a Public Release of Optical Data Products

The Blanco Cosmology Survey is a four-band (griz) optical-imaging survey of ~80 deg² of the southern sky. The survey consists of two fields centered approximately at (R.A., decl.) = (23^h, -55°) and (5^h30^m, -53°) with imaging sufficient for the detection of L _sstarf galaxies at redshift z <= 1. In this paper, we present our reduction of the survey data and describe a new technique for the separation of stars and galaxies. We search the calibrated source catalogs for galaxy clusters at z <= 0.75 by identifying spatial over-densities of red-sequence galaxies and report the coordinates, redshifts, and optical richnesses, λ, for 764 galaxy clusters at z <= 0.75. This sample, >85% of which are new discoveries, has a median redshift of z = 0.52 and median richness λ(0.4 L _sstarf) = 16.4. Accompanying this paper we also release full survey data products including reduced images and calibrated source catalogs. These products are available at http://data.rcc.uchicago.edu/dataset/blanco-cosmology-survey.