Preliminary Target Selection for the DESI Bright Galaxy Survey (BGS)

TL;DR

This paper discusses the target selection process for the DESI Bright Galaxy Survey, focusing on star-galaxy separation, masking, and resulting galaxy densities to optimize low-redshift galaxy observations for cosmological measurements.

Contribution

It introduces the specific target selection criteria and procedures for the DESI BGS, including star-galaxy separation and masking strategies, to improve survey accuracy.

Findings

Target densities of ~800 objects/deg^2 for BRIGHT and ~600 objects/deg^2 for FAINT.

Implementation of star-galaxy separation and masking reduces spurious targets.

Selection process enhances the precision of low-redshift galaxy clustering measurements.

Abstract

The Dark Energy Spectroscopic Instrument (DESI) will execute a nearly magnitude-limited survey of low redshift galaxies ($0.05 \leq z \leq 0.4$, median $z \approx 0.2$). Clustering analyses of this Bright Galaxy Survey (BGS) will yield the most precise measurements to date of baryon acoustic oscillations and redshift-space distortions at low redshift. DESI BGS will comprise two target classes: (i) BRIGHT ($r<19.5$~mag), and (ii) FAINT ($19.5<r<20$~mag). Here we present a summary of the star-galaxy separation, and different photometric and geometrical masks, used in BGS to reduce the number of spurious targets. The selection results in a total density of $\sim 800$ objects/deg$^2$ for the BRIGHT and $\sim 600$ objects/deg$^2$ for the FAINT selections.A full characterization of the BGS selection can be found in Ruiz-Macias et al. (2020).