Photometric redshifts and model spectral energy distributions of galaxies from the SDSS-III BOSS DR10 data

Abstract

We construct a set of model spectra specifically designed to match the colours of the Baryon Oscillation Spectroscopic Survey CMASS galaxies and to be used with photometric redshift template fitting techniques. As a basis, we use a set of spectral energy distributions(SEDs) of single and composite stellar population models. These models cannot describe well the whole colour range populated by the CMASS galaxies at all redshifts, wherefore we modify them by multiplying the SEDs with λ-β for λ > λi for different values of λi and β. When fitting these SEDs to the colours of the CMASS sample, with a burst and dust components in superposition, we can recreate the location in colour spaces inhabited by the CMASS galaxies. From the best-fitting models, we select a small subset in a two-dimensional plane, whereto the galaxies were mapped by a self-organizing map. These models are used for the estimation of photometric redshifts with a Bayesian template fitting code. The photometric redshifts with the novel templates have a very small outlier rate of 0.22 per cent, a low bias Δz/(1 + z)> = 2.0× 10-3, and scatter of σ68 = 0.026 in the rest frame. Using our models, the galaxy colours are reproduced to a better extent with the photometric redshifts of this work than with photometric redshifts of Sloan Digital Sky Survey.