The Construction of Large-scale Structure Catalogs for the Dark Energy Spectroscopic Instrument

TL;DR

This paper details the methodology for constructing large-scale structure catalogs from DESI spectroscopic data, enabling precise clustering analysis and robust statistical modeling of the universe's structure.

Contribution

It introduces a comprehensive pipeline for creating weighted LSS catalogs from DESI data, incorporating detailed observational history and allowing for future enhancements.

Findings

High-precision DESI footprint mapping achieved

Robustness tests integrated into catalog construction

Enhanced modeling of sample completeness and redshift assignment

Abstract

We present the technical details on how large-scale structure (LSS) catalogs are constructed from redshifts measured from spectra observed by the Dark Energy Spectroscopic Instrument (DESI). The LSS catalogs provide the information needed to determine the relative number density of DESI tracers as a function of redshift and celestial coordinates and, e.g., determine clustering statistics. We produce catalogs that are weighted subsamples of the observed data, each matched to a weighted `random' catalog that forms an unclustered sampling of the probability density that DESI could have observed those data at each location. Precise knowledge of the DESI observing history and associated hardware performance allows for a determination of the DESI footprint and the number of times DESI has covered it at sub-arcsecond level precision. This enables the completeness of any DESI sample to be modeled at this same resolution. The pipeline developed to create LSS catalogs has been designed to easily allow robustness tests and enable future improvements. We describe how it allows ongoing work improving the match between galaxy and random catalogs, such as including further information when assigning redshifts to randoms, accounting for fluctuations in target density, accounting for variation in the redshift success rate, and accommodating blinding schemes.