Validation of the Scientific Program for the Dark Energy Spectroscopic Instrument

Abstract

The Dark Energy Spectroscopic Instrument (DESI) was designed to conduct a survey covering 14,000 deg2 over 5 yr to constrain the cosmic expansion history through precise measurements of baryon acoustic oscillations (BAO). The scientific program for DESI was evaluated during a 5 month survey validation (SV) campaign before beginning full operations. This program produced deep spectra of tens of thousands of objects from each of the stellar Milky Way Survey (MWS), Bright Galaxy Survey (BGS), luminous red galaxy (LRG), emission line galaxy (ELG), and quasar target classes. These SV spectra were used to optimize redshift distributions, characterize exposure times, determine calibration procedures, and assess observational overheads for the 5 yr program. In this paper, we present the final target selection algorithms, redshift distributions, and projected cosmology constraints resulting from those studies. We also present a One-Percent Survey conducted at the conclusion of SV covering 140 deg2 using the final target selection algorithms with exposures of a depth typical of the main survey. The SV indicates that DESI will be able to complete the full 14,000 deg2 program with spectroscopically confirmed targets from the MWS, BGS, LRG, ELG, and quasar programs with total sample sizes of 7.2, 13.8, 7.46, 15.7, and 2.87 million, respectively. These samples will allow exploration of the Milky Way halo, clustering on all scales, and BAO measurements with a statistical precision of 0.28% over the redshift interval z < 1.1, 0.39% over the redshift interval 1.1 < z < 1.9, and 0.46% over the redshift interval 1.9 < z < 3.5.

Photometric Objects Around Cosmic Webs (PAC). VI. High Satellite Fraction of Quasars

“…With the forthcoming data from DESI (DESI Collaboration et al 2023;Adame et al 2024), we anticipate gaining a better understanding of quasar clustering, given the larger number of surveyed quasars compared to SDSS-IV. Additionally, with the quasar-halo connection determined by our SHAM method, we can generate quasar mocks for DESI.…”

Constraining primordial non-Gaussianity from DESI quasar targets and Planck CMB lensing

“…We use data drawn from both the DESI Early Data Release (EDR) [68] and from the first two months of first year release (DR1). We validate the redshifting and quasar classification pipeline with a small (∼1500) sample of visually inspected quasars from DESI Survey Validation [69], and check these results using the first two months of DR1 over a much wider area with a larger number of targets. DR1 redshift catalogs beyond the first two months of observing are blinded; we therefore only use the first two months of observations.…”

Measurement of the small-scale 3D Lyman-α forest power spectrum

“…Line-of-sight pairs with significantly smaller angular separations are observed solely due to fluctuations in the quasar sky distribution. However, the forthcoming spectroscopic surveys are expected to substantially increase the quasar density, for example the number density of z > 2.1 quasars for the main DESI sample will be n = 58 deg −2 [53]. Given that the number of pairs scales like n 2 , it is foreseeable that large-scale sky surveys will provide a sufficiently large statistical sample for the assessment of Lyα correlations at small r ⊥ .…”