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 the Sloan Digital Sky Survey Data Release 7 (SDSS‐DR7), available on the World Wide Web. The photometric redshifts were estimated with an artificial neural network using five ugriz bands, concentration indices and Petrosian radii in the g and r bands. We have explored our redshift estimates with different training sets, thus concluding that the best choice for improving redshift accuracy comprises the main galaxy sample (MGS), the luminous red galaxies and the galaxies of active galactic nuclei covering the redshift range 0 < z≤ 0.3. For the MGS, the photometric redshift estimates agree with the spectroscopic values within rms = 0.0227. The distribution of photometric redshifts derived in the range 0 < zphot≤ 0.6 agrees well with the model predictions. k‐corrections were derived by calibration of the k‐correct_v4.2 code results for the MGS with the reference‐frame (z= 0.1) (g−r) colours. We adopt a linear dependence of k‐corrections on redshift and (g−r) colours that provide suitable distributions of luminosity and colours for galaxies up to redshift zphot= 0.6 comparable to the results in the literature. Thus, our k‐correction estimate procedure is a powerful, low computational time algorithm capable of reproducing suitable results that can be used for testing galaxy properties at intermediate redshifts using the large SDSS data base.

Galaxy triplets in Sloan Digital Sky Survey Data Release 7 - I. Catalogue

“…k ‐corrections for this sample were calculated using the software k‐correct v4.2 of Blanton & Roweis (2007). The photometric data were derived from the photometric catalogue constructed by O’Mill et al (2011) 2 . These authors compute photometric redshift and k ‐correction for the photometric data of the SDSS DR7.…”

“…In this work, we present a catalogue of triplets of bright galaxies ( M r < −20.5) selected from a volume‐limited sample extracted from SDSS DR7 in the redshift range 0.01 ≤ z ≤ 0.4. We used data with both spectroscopic redshift measurements and photometric redshifts from O’Mill et al (2011).…”

The first analytical expression to estimate photometric redshifts suggested by a machine

“…Connolly et al 1995;Collister & Lahav 2004;Wadadekar 2005;Miles et al 2007;O'Mill et al 2011;Reis et al 2012;Carrasco Kind & Brunner 2013) and template-fitting-based methods (e.g., Benítez 2000;Bolzonella et al 2000;Ilbert et al 2006). The former uses magnitudes and/or colours of a spectroscopically measured sample for training the method, which is then applied to the photometric sample.…”

Optical Luminosity Function of the QSOs Observed with the Sloan Digital Sky Survey Data Release Seven (SDSS DR7)

“…The SDSS DR7 represents the completion of SDS-II phase (2005)(2006)(2007)(2008). It provides imaging data for 357 million distinct objects in the five bands (ugriz), as well as spectroscopy over π ≅ steradians in the North Galactic cap and 250 square degrees in the South Galactic cap [8]. This catalog covers an area of ≈9380 deg 2 .…”

“…The filters are placed on the camera in the order r , i , u , z , g [7]. The SDSS survey covers more than one-quarter of the entire sky which performing photometry and spectroscopy for galaxies, stars and quasars [8].…”