Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 375, Issue 1, Pages 68-76Publisher
WILEY-BLACKWELL
DOI: 10.1111/j.1365-2966.2006.11305.x
Keywords
catalogues; surveys; galaxies : distances and redshifts; cosmology : observations
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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 sigma(z) 0.049 averaged over all galaxies, and sigma(z) = 0.040 for a brighter subsample (i < 19.0). The catalogue is expected to contain similar to 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.
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