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The Blanco Cosmology Survey


The Blanco Cosmology Survey (BCS) is a 60 night imaging survey of ~80 deg2 of the southern sky located in two fields: (α, δ) = (5 hr, -55°) and (23 hr, -55°). The survey was carried out between 2005 and 2008 in grizbands with the Mosaic2 imager on the CTIO Blanco 4-m telescope. The primary aim of the BCS survey is to provide the data required to optically confirm and measure photometric redshifts for Sunyaev-Zel'dovich effect selected galaxy clusters from the South Pole Telescope and the Atacama Cosmology Telescope. The median 10σ galaxy (point-source) depths over the survey in grizare approximately 23.3 (23.9), 23.4 (24.0), 23.0 (23.6), and 21.3 (22.1), respectively. The astrometric accuracy relative to the USNO-B survey is ~45 mas. Absolute photometry is calibrated using the stellar locus in grizJbands; the absolute photometric scale has ~2% accuracy. The scatter of stars about the stellar locus indicates a systematic floor in the relative stellar photometric scatter in grizthat is ~1.9%, ~2.2%, ~2.7%, and ~2.7%, respectively.

BCS at a Glance

PI(s) Joseph Mohr
Proposal ID 2005B-0043
Years of Observation 2005-2008
Sample: Image mosaics of two survey areas, covering ~45 deg2 at (α, δ) = (5 hr, -55°) and ~35 deg2 at (α, δ) = (23 hr, -55°)
Bands g, r, i, z
Median Depth (10σ) (g, r, i, z) = (23.9, 24.0, 23.6, 22.1)
Median Seeing (g, r, i, z) = (1.1, 1,0, 1.0, and 1.0) arcsec
Number of images 928