Carles Sánchez - True Bayesian redshifts in the Dark Energy Survey

Wednesday 25 Jul 2018, 13:00 → 14:00 Europe/Madrid

Seminar (IFAE)

Marc Manera (IFAE), Stefano Terzo (IFAE)

Some of the most important current and future cosmological constraints, coming from high precision measurements of the large-scale structure of galaxies and its weak gravitational lensing effects, rely on photometry of galaxies by experiments such as the Dark Energy Survey (DES). The redshift of galaxies in such missions, arguably one of the most important observables, needs to be derived from photometry only, with the so-called photometric redshift technique. The associated systematic uncertainties coming from the methods currently used are likely to overcome statistical uncertainties in the near future, and hence new developments are needed in the field. In this talk, I will describe a hierarchical Bayesian model (HBM) which provides full posterior distributions on both the redshift probability distributions of galaxy populations and the redshifts of their individual members, and, for the first time, we show how to combine survey photometry of single galaxies and the information contained in the galaxy clustering against a well-characterized tracer population in a robust way. The incorporation of clustering information with photometric redshifts not only tightens redshift posteriors, but can also critically overcome biases or gaps in the coverage of a spectroscopic prior. I will finish by outlining the application of this method to upcoming data analyses in DES.