DESI Early Data Release Milky Way Survey Value-Added Catalogue

TL;DR

This paper introduces the first DESI Milky Way Survey value-added stellar catalogue with radial velocities and stellar parameters for about 400,000 stars, validated for accuracy and useful for galactic studies.

Contribution

It provides the initial DESI MWS catalogue with validated stellar measurements and guidelines for sample selection, setting the stage for future larger data releases.

Findings

Radial velocities accurate to 1 km/s

Surface gravities accurate to 0.3 dex

Iron abundances accurate to 0.15 dex

Abstract

We present the stellar value-added catalogue based on the Dark Energy Spectroscopic Instrument (DESI) Early Data Release. The catalogue contains radial velocity and stellar parameter measurements for $\simeq$ 400,000 unique stars observed during commissioning and survey validation by DESI. These observations were made under conditions similar to the Milky Way Survey (MWS) currently carried out by DESI but also include multiple specially targeted fields, such as those containing well-studied dwarf galaxies and stellar streams. The majority of observed stars have $16<r<20$ with a median signal-to-noise ratio in the spectra of $\sim$ 20. In the paper, we describe the structure of the catalogue, give an overview of different target classes observed, as well as provide recipes for selecting clean stellar samples. We validate the catalogue using external high-resolution measurements and show that radial velocities, surface gravities, and iron abundances determined by DESI are accurate to 1 km/s, $0.3$ dex and $\sim$ 0.15 dex respectively. We also demonstrate possible uses of the catalogue for chemo-dynamical studies of the Milky Way stellar halo and Draco dwarf spheroidal. The value-added catalogue described in this paper is the very first DESI MWS catalogue. The next DESI data release, expected in less than a year, will add the data from the first year of DESI survey operations and will contain approximately 4 million stars, along with significant processing improvements.