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

Authors

  • Ana Laura O'Mill,

    Corresponding author
    1. Instituto de Astronomía Teórica y Experimental, IATE, Observatorio Astronómico, Universidad Nacional de Córdoba, Laprida 854, X5000BGR Córdoba, Argentina
    2. Consejo de Investigaciones Científicas y Técnicas (CONICET), Avenida Rivadavia 1917, C1033AAJ Buenos Aires, Argentina
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  • Fernanda Duplancic,

    1. Instituto de Astronomía Teórica y Experimental, IATE, Observatorio Astronómico, Universidad Nacional de Córdoba, Laprida 854, X5000BGR Córdoba, Argentina
    2. Consejo de Investigaciones Científicas y Técnicas (CONICET), Avenida Rivadavia 1917, C1033AAJ Buenos Aires, Argentina
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  • Diego García Lambas,

    1. Instituto de Astronomía Teórica y Experimental, IATE, Observatorio Astronómico, Universidad Nacional de Córdoba, Laprida 854, X5000BGR Córdoba, Argentina
    2. Consejo de Investigaciones Científicas y Técnicas (CONICET), Avenida Rivadavia 1917, C1033AAJ Buenos Aires, Argentina
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  • Laerte Sodré, Jr

    1. Departamento de Astronomia, Instituto de Astronomia, Geofísica e Ciências Atmosféricas da USP, Rua do Matão 1226, Cidade Universitária, 05508-090 São Paulo, Brazil
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E-mail: aomill@oac.uncor.edu

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) (gr) colours. We adopt a linear dependence of k-corrections on redshift and (gr) 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.

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