J/ApJ/757/83 The Blanco Cosmology Survey (BCS) (Desai+, 2012)
The Blanco Cosmology Survey: data acquisition, processing, calibration,
quality diagnostics, and data release.
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.
<Astrophys. J., 757, 83 (2012)>
=2012ApJ...757...83D 2012ApJ...757...83D
ADC_Keywords: Photometry, ugriz ; Redshifts ; Surveys
Keywords: cosmology: observations; galaxies: clusters: general;
methods: data analysis; surveys; techniques: image processing
Abstract:
The Blanco Cosmology Survey (BCS) is a 60 night imaging survey of
∼80deg2 of the southern sky located in two fields: (5hr,-55°)
and (23hr,-55°). The survey was carried out between 2005 and 2008
in griz bands with the Mosaic2 imager on the Blanco 4m 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
10σ 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 ∼45mas. 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
δz/(1+z)=0.054 with an outlier fraction η<5% to z∼1. We
highlight some selected science results to date and provide a full
description of the released data products.
Description:
The Blanco Cosmology Survey (BCS), ∼80deg2, was a NOAO Large Survey
project (2005B-0043, PI: Joseph Mohr) which was awarded 60 nights
between 2005 (starting from semester 2005B) and 2008 on the Cerro
Tololo Inter American Observatory (CTIO) Blanco 4m telescope using the
Mosaic2 imager with griz bands. Because of shared nights with other
programs, the data acquisition included 69 nights, and the final
processed data set only consists of 66 nights.
The survey was divided into two fields to allow efficient use of the
allocated nights between October and December. Both fields lie near
δ=-55° which allows for overlap with the SPT (South Pole
telescope) and other mm-wave surveys. One field is centered near
α=23.5hr and the other is at α=5.5hr. The BCS observing
strategy was designed to allow us to accurately measure cluster
photometric redshifts out to redshift z=1.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
bcs05hr.dat 474 3454220 *BCS 5hr catalog (combined catalog of 5hr field
after EXCLUDING bad tiles)
bcs23hr.dat 474 2176966 *BCS 23hr catalog (combined catalog of 23hr field
after EXCLUDING bad tiles)
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Note on bcs05hr.dat bcs23hr.dat: More details on some of the parameters can
be found in the SExtractor manual. The magnitudes are corrected for
galactic extinction.
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See also:
III/268 : DEEP2 Redshift Survey, Data Release 4 (Matthews+ 2013)
III/250 : The VIMOS VLT deep survey (VVDS-DEEP) (Le Fevre+ 2005)
VII/110 : Rich Clusters of Galaxies (Abell+ 1989)
VII/4 : Abell and Zwicky Clusters of Galaxies (Abell+ 1974)
J/ApJ/742/48 : Blanco survey of the lens BCS J2352-5452 (Buckley-Geer+, 2011)
J/ApJS/191/340 : Southern Cosmology Survey. II. (Menanteau+, 2010)
J/A+A/509/A81 : Candidate clusters detected in 6 CFHTLS fields (Adami+, 2010)
J/AJ/137/2981 : Northern Optical Cluster Survey. III. (Gal+, 2009)
J/MNRAS/375/68 : MegaZ-LRG catalogue (Collister+, 2007)
J/AJ/134/2398 : Stellar SEDs in SDSS and 2MASS filters (Covey+, 2007)
J/ApJ/660/239 : MaxBCG cat. of 13823 SDSS galaxy clusters (Koester+, 2007)
J/A+A/428/1043 : Redshifts from VIMOS VLT Deep Survey (Le Fevre+, 2004)
J/ApJS/137/117 : Las Campanas Distant Cluster Survey (LCDCS) (Gonzales+, 2001)
J/ApJS/129/475 : The CNOC2 survey. I. (Yee+, 2000)
http://www.usm.uni-muenchen.de/BCS : BCS home page
Byte-by-byte Description of file: bcs05hr.dat bcs23hr.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- --- [BCS]
4- 12 A9 --- Tile Name of tile (HHMM+DDMM) (tilename) (1)
14- 22 I9 --- ID [692766381/704461337] Identifier number from
DESDM database (objectid) (2)
24- 32 F9.5 deg RAdeg Right ascension (J2000) (RA)
34- 42 F9.5 deg DEdeg Declination (J2000) (DEC)
44- 50 F7.3 mag gmag [4.9/47]?=99 Model g-band AB magnitude
(magmodelg)
52- 58 F7.3 mag e_gmag [0/99]?=99 gmag uncertainty (magerrmodelg)
60- 66 F7.3 mag gauto [6.9/40]?=99 Kron g-band AB magnitude
(magautog)
68- 74 F7.3 mag e_gauto [0/99]?=99 gauto uncertainty (magerrautog)
76- 82 F7.3 mag gpsf [10.7/32]?=99 PSF g-band AB magnitude
(magpsfg)
84- 90 F7.3 mag e_gpsf [0/99]?=99 gpsf uncertainty (magerrpsfg)
92- 98 F7.3 mag gpetro [6.8/42]?=99 Petrosian g-band AB magnitude
(magpetrog)
100-106 F7.3 mag e_gpetro [0/99]?=99 gpetro uncertainty (magerrpetrog)
108-114 F7.3 mag gap3 [11.1/41]?=99 g-band AB magnitude in 3arcsec
aperture (magaper3g)
116-122 F7.3 mag e_gap3 [0/99]?=99 gap3 uncertainty (magerraper3g)
124-125 I2 --- gfl [0/92] SExtractor flag (flags_g)
127-130 F4.2 --- gS/G [0/1] SExtractor star/galaxy separator
(0=galaxy, 1=star) (classstarg)
132-138 F7.3 mag gDiff [-99/99] Difference in PSF and Sersic
magnitude (g) (spreadmodelg)
140-146 F7.3 mag e_gDiff [0/99]?=99 gDiff uncertainty (spreadmodelerrg)
148-154 F7.3 mag rmag [5.7/45]?=99 Model r-band AB magnitude
(magmodelr)
156-162 F7.3 mag e_rmag [0/99]?=99 rmag uncertainty (magerrmodelr)
164-170 F7.3 mag rauto [7.6/42]?=99 Kron r-band AB magnitude
(magautor)
172-178 F7.3 mag e_rauto [0/99]?=99 rauto uncertainty (magerrautor)
180-186 F7.3 mag rpsf [12.4/32]?=99 PSF r-band AB magnitude
(magpsfr)
188-194 F7.3 mag e_rpsf [0/99]?=99 rpsf uncertainty (magerrpsfr)
196-202 F7.3 mag rpetro [7.5/40]?=99 Petrosian r-band AB magnitude
(magpetror)
204-210 F7.3 mag e_rpetro [0/99]?=99 rpetro uncertainty (magerrpetror)
212-218 F7.3 mag rap3 [12.9/38]?=99 r-band AB magnitude in 3arcsec
aperture (magaper3r)
220-226 F7.3 mag e_rap3 [0/99]?=99 rap3 uncertainty (magerraper3r)
228-229 I2 --- rfl [0/92] SExtractor flag (flags_r)
231-234 F4.2 --- rS/G [0/1] SExtractor star/galaxy separator
(0=galaxy, 1=star) (classstarr)
236-242 F7.3 mag rDiff [-99/99] Difference in PSF and Sersic
magnitude (r) (spreadmodelr)
244-250 F7.3 mag e_rDiff [0/99]?=99 rDiff uncertainty (spreadmodelerrr)
252-258 F7.3 mag imag [3.1/42] Model i-band AB magnitude
(magmodeli)
260-266 F7.3 mag e_imag [0/99]?=99 imag uncertainty (magerrmodeli)
268-274 F7.3 mag iauto [3.7/40]?=99 Kron i-band AB magnitude
(magautoi)
276-282 F7.3 mag e_iauto [0/99]?=99 iauto uncertainty (magerrautoi)
284-290 F7.3 mag ipsf [-24.6/29]?=99 PSF i-band AB magnitude
(magpsfi)
292-298 F7.3 mag e_ipsf [0/99]?=99 ipsf uncertainty (magerrpsfi)
300-306 F7.3 mag ipetro [3.7/40]?=99 Petrosian i-band AB magnitude
(magpetroi)
308-314 F7.3 mag e_ipetro [0/99]?=99 ipetro uncertainty (magerrpetroi)
316-322 F7.3 mag iap3 [7.3/36]?=99 i-band AB magnitude in 3arcsec
aperture (magaper3i)
324-330 F7.3 mag e_iap3 [0/99]?=99 iap3 uncertainty (magerraper3i)
332-333 I2 --- ifl [0/92] SExtractor flag (flags_i)
335-338 F4.2 --- iS/G [0/1] SExtractor star/galaxy separator
(0=galaxy, 1=star) (classstari)
340-346 F7.3 mag iDiff [-99/99] Difference in PSF and Sersic
magnitude (i) (spreadmodeli)
348-354 F7.3 mag e_iDiff [0/99]?=99 iDiff uncertainty (spreadmodelerri)
356-362 F7.3 mag zmag [4/44] Model z-band AB magnitude
(magmodelz)
364-370 F7.3 mag e_zmag [0/99]?=99 zmag uncertainty (magerrmodelz)
372-378 F7.3 mag zauto [6.4/40]?=99 Kron z-band AB magnitude
(magautoz)
380-386 F7.3 mag e_zauto [0/99]?=99 zauto uncertainty (magerrautoz)
388-394 F7.3 mag zpsf [10.6/27]?=99 PSF z-band AB magnitude
(magpsfz)
396-402 F7.3 mag e_zpsf [0/99]?=99 zpsf uncertainty (magerrpsfz)
404-410 F7.3 mag zpetro [6.4/39]?=99 Petrosian i-band AB magnitude
(magpetroz)
412-418 F7.3 mag e_zpetro [0/99]?=99 zpetro uncertainty (magerrpetroz)
420-426 F7.3 mag zap3 [11.3/37]?=99 z-band AB magnitude in 3arcsec
aperture (magaper3z)
428-434 F7.3 mag e_zap3 [0/99]?=99 zap3 uncertainty (magerraper3z)
436-437 I2 --- zfl [0/92] SExtractor flag (flags_z)
439-442 F4.2 --- zS/G [0/1] SExtractor star/galaxy separator
(0=galaxy, 1=star) (classstarz)
444-450 F7.3 mag zDiff [-99/99] Difference in PSF and Sersic
magnitude (z) (spreadmodelz)
452-458 F7.3 mag e_zDiff [0/99]?=99 zDiff uncertainty (spreadmodelerrz)
460-464 F5.2 --- z [-0.06/3.1] Photometric redshift (z_phot)
466-470 F5.2 --- e_z [0.01/99]?=99 z uncertainty (zphoterr)
472-474 F3.1 --- n_z [0/1] Within ANNZ training set parameter space
(zphotflag) (3)
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Note (1): For convenience of data processing and building catalogs, we divide
the survey region into 36'x36' square regions called tiles. Each tile
is a 8192x8192 pixel portion of a tangent plane projection. These
tiles are set on a grid of point separated by 34', allowing for
approximately 1' overlaps of sky between neighboring tiles.
See section 2.2 for further explanations.
Note (2): The processing of BCS data is carried out using the automated Dark
Energy Survey Data Management (DESDM) system which has been under
development since Fall 2005 at University of Illinois (Ngeow et al.
2006SPIE.6270E..68N 2006SPIE.6270E..68N; Mohr et al. 2008SPIE.7016E..17M 2008SPIE.7016E..17M).
Note (3): ANNz is a feed-forward multi-layer perceptron network designed for
finding photometric redshifts (Collister & Lahav 2004PASP..116..345C 2004PASP..116..345C;
see also section 4). The values are:
1 = if object is in the ANNz training domain (i.e. it would pass the selection
criteria used for building the training set for the ANNz network),
0 = otherwise.
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History:
Copied at http://www.usm.uni-muenchen.de/BCS/: BCS23hr_Mar30.cat and
BCS05hr_Mar30.cat (04-Jan-2014)
(End) Emmanuelle Perret [CDS] 11-Jun-2014