Overview of the DESI Legacy Imaging Surveys

TL;DR

The DESI Legacy Imaging Surveys combine three major projects to image a large portion of the extragalactic sky in optical and infrared bands, providing calibrated images and catalogs with uniform depth and extensive data releases.

Contribution

This paper presents an overview of the DESI Legacy Imaging Surveys, detailing their scope, methodology, data products, and plans for public data releases.

Findings

Survey covers ~14,000 deg^2 of extragalactic sky.

Provides calibrated images and probabilistic source catalogs.

Includes optical and mid-infrared photometry from multiple surveys.

Abstract

The DESI Legacy Imaging Surveys are a combination of three public projects (the Dark Energy Camera Legacy Survey, the Beijing-Arizona Sky Survey, and the Mayall z-band Legacy Survey) that will jointly image approximately 14,000 deg^2 of the extragalactic sky visible from the northern hemisphere in three optical bands (g, r, and z) using telescopes at the Kitt Peak National Observatory and the Cerro Tololo Inter-American Observatory. The combined survey footprint is split into two contiguous areas by the Galactic plane. The optical imaging is conducted using a unique strategy of dynamically adjusting the exposure times and pointing selection during observing that results in a survey of nearly uniform depth. In addition to calibrated images, the project is delivering a catalog, constructed by using a probabilistic inference-based approach to estimate source shapes and brightnesses. The catalog includes photometry from the grz optical bands and from four mid-infrared bands (at 3.4, 4.6, 12 and 22 micorons) observed by the Wide-field Infrared Survey Explorer (WISE) satellite during its full operational lifetime. The project plans two public data releases each year. All the software used to generate the catalogs is also released with the data. This paper provides an overview of the Legacy Surveys project.