J/MNRAS/375/68 MegaZ-LRG catalogue (Collister+, 2007)
MegaZ-LRG: a photometric redshift catalogue of one million
SDSS luminous red galaxies.
Collister A., Lahav O., Blake C., Cannon R., Croom S., Drinkwater M.,
Edge A., Eisenstein D., Loveday J., Nichol R., Pimbblet K., De Propris R.,
Roseboom I., Ross N., Schneider D.P., Shanks T., Wake D.
<Mon. Not. R. Astron. Soc., 375, 68-76 (2007)>
=2007MNRAS.375...68C 2007MNRAS.375...68C
ADC_Keywords: Surveys ; Galaxy catalogs ; Redshifts ; Galaxies, photometry
Keywords: catalogues - surveys - galaxies: distances and redshifts -
cosmology: observations
Abstract:
We describe the construction of MegaZ-LRG, a photometric redshift
catalogue of over one million luminous red galaxies (LRGs) in the
redshift range 0.4<z<0.7 with limiting magnitude i<20. The catalogue
is selected from the imaging data of the Sloan Digital Sky Survey
(SDSS) Data Release 4. The 2dF-SDSS LRG and Quasar (2SLAQ)
spectroscopic redshift catalogue of 13000 intermediate-redshift LRGs
provides a photometric redshift training set, allowing use of ANNZ, a
neural network-based photometric-redshift estimator. The rms
photometric redshift accuracy obtained for an evaluation set selected
from the 2SLAQ sample is z=0.049 averaged over all galaxies, and
z=0.040 for a brighter subsample (i<19.0). The catalogue is expected
to contain ∼5 per cent stellar contamination. The ANNZ code is used to
compute a refined star/galaxy probability based on a range of
photometric parameters; this allows the contamination fraction to be
reduced to 2 per cent with negligible loss of genuine galaxies. The
MegaZ-LRG catalogue is publicly available on the World Wide Web from
http://www.2slaq.info .
Description:
MegaZ-LRG is based on SDSS five-band (ugriz) imaging data obtained
with a large format CCD camera mounted on a special-purpose 2.5-m
telescope located at Apache Point Observatory in New Mexico.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
catalog.dat 92 1214117 MegaZ-LRG photometric redshift catalogue
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See also:
II/267 : The SDSS Photometric Catalog, Release 4 (Adelman-McCarthy+, 2006)
VII/241 : The 2dF QSO Redshift Survey (Croom+ 2004)
J/MNRAS/372/425 : 2dF-SDSS Luminous Red Galaxy Survey, 2SLAQ (Cannon+, 2006)
http://www.sdss.org/ : SDSS Home Page
http://www.2slaq.info : 2SLAQ Website
Byte-by-byte Description of file: catalog.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- SDSS SDSS object identification number
20- 28 F9.5 deg RAdeg Right ascension in decimal degrees (J2000)
29- 37 F9.5 deg DEdeg Declination in decimal degrees (J2000)
40- 45 F6.3 mag umag ?=99.999 Dereddened u band magnitude
47- 52 F6.3 mag gmag Dereddened g band magnitude
54- 59 F6.3 mag rmag Dereddened r band magnitude
61- 66 F6.3 mag imag Dereddened i band magnitude
68- 73 F6.3 mag zmag Dereddened z band magnitude
75- 80 F6.3 mag i(dev) Dereddened de Vaucouleurs i band magnitude
82- 86 F5.3 --- zph ANNZ Photometric redshift (2)
88- 92 F5.3 --- S/G [0,1] ANNZ Star/galaxy class (3)
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Note (2): ANNZ software package may be obtained from
http://www.star.ucl.ac.uk/~lahav/annz.html
Note (3): Value 1 indicates the target is most likely a galaxy.
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History:
Copied at http://www.2slaq.info
(End) Francois Ochsenbein, Patricia Vannier [CDS] 03-Sep-2007