Photometric Redshifts with Surface Brightness Priors

TL;DR

This paper demonstrates that incorporating galaxy surface brightness as a prior significantly enhances photometric redshift accuracy by reducing outliers and bias, especially in large-scale surveys.

Contribution

The authors introduce a surface brightness prior into template-based photo-z estimation, improving accuracy and reducing outliers across ground and space data.

Findings

Bias and scatter are improved by about a factor of 2.

The surface brightness prior reduces degeneracies between spectral features.

Effective application depends on image quality and size measurement accuracy.

Abstract

We use galaxy surface brightness as prior information to improve photometric redshift (photo-z) estimation. We apply our template-based photo-z method to imaging data from the ground-based VVDS survey and the space-based GOODS field from HST, and use spectroscopic redshifts to test our photometric redshifts for different galaxy types and redshifts. We find that the surface brightness prior eliminates a large fraction of outliers by lifting the degeneracy between the Lyman and 4000 Angstrom breaks. Bias and scatter are improved by about a factor of 2 with the prior for both the ground and space data. Ongoing and planned surveys from the ground and space will benefit, provided that care is taken in measurements of galaxy sizes and in the application of the prior. We discuss the image quality and signal-to-noise requirements that enable the surface brightness prior to be successfully applied.