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MegaZ-LRG: a photometric redshift catalogue of one million SDSS luminous red galaxies

Collister, Adrian; Lahav, Ofer; Blake, Chris; Cannon, Russell; Croom, Scott; Drinkwater, Michael; Edge, Alastair; Eisenstein, Daniel; Loveday, Jon; Nichol, Robert; Pimbblet, Kevin; De Propris, Roberto; Roseboom, Isaac; Ross, Nic; Schneider, Donald P.; Shanks, Tom and Wake, David (2007). MegaZ-LRG: a photometric redshift catalogue of one million SDSS luminous red galaxies. Monthly Notices of the Royal Astronomical Society, 375(1) pp. 68–76.

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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 13 000 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 σz = 0.049 averaged over all galaxies, and σz = 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

Item Type: Journal Item
Copyright Holders: 2007 The Authors
ISSN: 1365-2966
Keywords: galaxies; redshifts; cosmology
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Physical Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
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Item ID: 38519
Depositing User: Miranda Callaway
Date Deposited: 27 Sep 2013 08:25
Last Modified: 09 Dec 2018 20:13
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