All-purpose, all-sky photometric redshifts for the Legacy Imaging Surveys Data Release 8

Understand

In this paper we present photometric redshift (photo-$z$) estimates for the Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Surveys, currently the most sensitive optical survey covering the majority of the extra-galactic sky.

• Our photo-$z$ methodology is based on a machine-learning approach, using sparse Gaussian processes augmented with Gaussian mixture models (GMMs) that allow regions of parameter space to be identified and trained separately in a purely data-driven way.
• The same GMMs are also used to calculate cost-sensitive learning weights that mitigate biases in the spectroscopic training sample.
• By design, this approach aims to produce reliable and unbiased predictions for all parts of the parameter space present in wide area surveys.