THE BLANCO COSMOLOGY SURVEY: DATA ACQUISITION, PROCESSING, CALIBRATION, QUALITY DIAGNOSTICS, AND DATA RELEASE

• Published in: The Astrophysical journal Vol. 757; no. 1; pp. 83 - 22
• Main Authors: Desai, S., Armstrong, R., Mohr, J. J., Semler, D. R., Liu, J., Bertin, E., Allam, S. S., Barkhouse, W. A., Bazin, G., Buckley-Geer, E. J., Cooper, M. C., Hansen, S. M., High, F. W., Lin, H., Lin, Y.-T., Ngeow, C.-C., Rest, A., Song, J., Tucker, D., Zenteno, A.
• Format: Journal Article
• Language: English
• Published: Bristol IOP 20.09.2012; American Astronomical Society
• Subjects: ACCURACY; Astronomy; Astrophysics; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; Bands; CALIBRATION; CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; COSMOLOGY; DATA ACQUISITION; DATA PROCESSING; Earth, ocean, space; Exact sciences and technology; GALAXY CLUSTERS; PHOTOMETRY; RED SHIFT; Scatter; Sciences of the Universe; SKY; STARS; TELESCOPES; USES; Antarctica, South Pole; Data analysis; Red shift; galaxies: clusters: general; methods: data analysis; Galaxies; Image processing; surveys; Point spread functions; Galaxy clusters; Point sources; Sunyaev Zeldovich effect; techniques: image processing; Astronomical catalogues; Cosmology; Models; cosmology: observations; Sky surveys; Photometry; Astrophysics - Cosmology and Extragalactic Astrophysics
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/757/1/83

The Blanco Cosmology Survey (BCS) is a 60 night imaging survey of ~80 deg super(2) of the southern sky located in two fields: ([alpha], [delta]) = (5 hr, -55[degrees]) and (23 hr, -55[degrees]). The survey was carried out between 2005 and 2008 in griz bands with the Mosaic2 imager on the 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. We process and calibrate the BCS data, carrying out point-spread function-corrected model-fitting photometry for all detected objects. The median 10[sigma] galaxy (point-source) depths over the survey in griz are 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. We calibrate our absolute photometry using the stellar locus in grizJ bands, and thus our absolute photometric scale derives from the Two Micron All Sky Survey, which has ~2% accuracy. The scatter of stars about the stellar locus indicates a systematic floor in the relative stellar photometric scatter in griz that is ~1.9%, ~2.2%, ~2.7%, and ~2.7%, respectively. A simple cut in the AstrOmatic star-galaxy classifier spread_model produces a star sample with good spatial uniformity. We use the resulting photometric catalogs to calibrate photometric redshifts for the survey and demonstrate scatter [delta]z/(1 + z) = 0.054 with an outlier fraction [eta] < 5% to z ~ 1. We highlight some selected science results to date and provide a full description of the released data products.