Photometric redshifts and K-corrections for Sloan Digital Sky Survey Seven Data Release

TL;DR

This paper provides a catalog of galaxy photometric redshifts and k-corrections for SDSS DR7, using neural networks and calibration techniques to enable efficient analysis of galaxy properties up to redshift 0.6.

Contribution

It introduces a new method combining neural networks and calibration for accurate photometric redshifts and k-corrections in SDSS data, optimized for large datasets.

Findings

Photometric redshifts agree with spectroscopic values within rms=0.0227 for MGS.

Redshift distribution matches model predictions up to z=0.6.

Proposed k-correction method is fast and effective for large surveys.

Abstract

We present a catalogue of galaxy photometric redshifts and k-corrections for the Sloan Digital Sky Survey Seven Data Release (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 set concluding that the best choice to improve redshift accuracy comprises the Main Galaxies Sample (MGS), the Luminous Red Galaxies, and 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 derived distribution of photometric redshifts 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 database.