Photometric redshifts and k-corrections for the Sloan Digital Sky Survey Data Release 7

Abstract

We present a catalogue of galaxy photometric redshifts and k-corrections for\nthe Sloan Digital Sky Survey Seven Data Release (SDSS-DR7), available on the\nWorld Wide Web. The photometric redshifts were estimated with an artificial\nneural network using five ugriz bands, concentration indices and Petrosian\nradii in the g and r bands. We have explored our redshift estimates with\ndifferent training set concluding that the best choice to improve redshift\naccuracy comprises the Main Galaxies Sample (MGS), the Luminous Red Galaxies,\nand galaxies of active galactic nuclei covering the redshift range 0<z<0.3. For\nthe MGS, the photometric redshift estimates agree with the spectroscopic values\nwithin rms=0.0227. The derived distribution of photometric redshifts in the\nrange 0<zphot<0.6 agrees well with the model predictions. k-corrections were\nderived by calibration of the k-correct-v4.2 code results for the MGS with the\nreference frame (z=0.1) (g-r) colours. We adopt a linear dependence of k\ncorrections on redshift and (g-r) colours that provide suitable distributions\nof luminosity and colours for galaxies up to redshift zphot=0.6 comparable to\nthe results in the literature. Thus, our k-correction estimate procedure is a\npowerful, low computational time algorithm capable of reproducing suitable\nresults that can be used for testing galaxy properties at intermediate\nredshifts using the large SDSS database.\n