Dark Energy Survey Year 3 Results: Deep Field Optical + Near-Infrared Images and Catalogue

TL;DR

This paper presents the DES Deep Fields catalog, combining optical and near-infrared data over 30 square degrees, with advanced source deblending, precise photometry, and high-quality photometric redshifts for cosmological analysis.

Contribution

It introduces a new multi-wavelength catalog with improved deblending, PSF modeling, and photometric redshift accuracy, supporting DES's 3-year cosmology research.

Findings

Catalog contains 2.8 million objects with high-quality photometry.

Achieved excellent photometric redshift performance with NMAD = 0.023.

Demonstrated precise star-galaxy separation and consistent multi-band photometry.

Abstract

We describe the Dark Energy Survey (DES) Deep Fields, a set of images and associated multi-wavelength catalogue ($ugrizJHKs$) built from Dark Energy Camera (DECam) and Visible and Infrared Survey Telescope for Astronomy (VISTA) data. The DES Deep Fields comprise 11 fields (10 DES supernova fields plus COSMOS), with a total area of $\sim30~$ square degrees in $ugriz$ bands and reaching a maximum $i$-band depth of 26.75 (AB, $10\sigma$, 2 arcsec). We present a catalogue for the DES 3-year cosmology analysis of those four fields with full 8-band coverage, totalling $5.88~$ sq. deg. after masking. Numbering $2.8~$million objects ($1.6~$million post masking), our catalogue is drawn from images coadded to consistent depths of $r=25.7, i=25, z=24.3$ mag. We use a new model-fitting code, built upon established methods, to deblend sources and ensure consistent colours across the $u$-band to $Ks$-band wavelength range. We further detail the tight control we maintain over the point-spread function modelling required for the model fitting, astrometry and consistency of photometry between the four fields. The catalogue allows us to perform a careful star-galaxy separation and produces excellent photometric redshift performance (${\rm NMAD} = 0.023$ at $i<23$). The Deep-Fields catalogue will be made available as part of the cosmology data products release, following the completion of the DES 3-year weak lensing and galaxy clustering cosmology work.