DESI 2024 II: Sample Definitions, Characteristics, and Two-point Clustering Statistics

TL;DR

This paper details the construction, correction, and analysis of galaxy and quasar samples from DESI DR1 for cosmological studies, including 2-point clustering measurements and their validation against simulations.

Contribution

It introduces comprehensive LSS catalogs with systematic corrections and measurement pipelines for DESI DR1, enabling accurate clustering analysis and public data release.

Findings

2 ext{--}3 ext{ }% agreement between data and simulations in clustering measurements

Effective correction methods for observational systematics

Public release of catalogs and covariance matrices

Abstract

We present the samples of galaxies and quasars used for DESI 2024 cosmological analyses, drawn from the DESI Data Release 1 (DR1). We describe the construction of large-scale structure (LSS) catalogs from these samples, which include matched sets of synthetic reference `randoms' and weights that account for variations in the observed density of the samples due to experimental design and varying instrument performance. We detail how we correct for variations in observational completeness, the input `target' densities due to imaging systematics, and the ability to confidently measure redshifts from DESI spectra. We then summarize how remaining uncertainties in the corrections can be translated to systematic uncertainties for particular analyses. We describe the weights added to maximize the signal-to-noise of DESI DR1 2-point clustering measurements. We detail measurement pipelines applied to the LSS catalogs that obtain 2-point clustering measurements in configuration and Fourier space. The resulting 2-point measurements depend on window functions and normalization constraints particular to each sample, and we present the corrections required to match models to the data. We compare the configuration- and Fourier-space 2-point clustering of the data samples to that recovered from simulations of DESI DR1 and find they are, generally, in statistical agreement to within 2\% in the inferred real-space over-density field. The LSS catalogs, 2-point measurements, and their covariance matrices will be released publicly with DESI DR1.