One-dimensional power spectrum from first DESI Lyman-{\alpha} forest

TL;DR

This paper presents the first measurement of the one-dimensional Lyman-alpha forest power spectrum from DESI data, improving resolution and validating methodology, which will help constrain cosmological parameters.

Contribution

First measurement of the Lyman-alpha forest power spectrum from DESI data using FFT estimator, with validation and correction for contaminants.

Findings

Improved spectroscopic resolution over previous measurements

Validated measurement with synthetic data and correction for contaminants

Agreement with quadratic maximum likelihood estimator results

Abstract

The Lyman-alpha forest is a unique probe of large-scale matter density fluctuations at high redshift z > 2. We measure the one-dimensional Lyman-alpha forest power spectrum using the first data provided by the Dark Energy Spectroscopic Instrument (DESI), with a fast Fourier transform estimator. The data sample contains quasar spectra included in the DESI Early Data Release and the first two months of the main survey. This first set of data already provides an improvement in terms of spectroscopic resolution with respect to the previous measurements. We investigated methodological and instrumental contaminants associated with DESI and used synthetic data to validate and correct our measurement. Coupling our measurement with theoretical predictions from hydrodynamical simulations will yield strong constraints on the primordial matter power spectrum, neutrino masses, and dark matter properties. A quadratic maximum likelihood estimator was applied to the same data set on a companion paper and agrees with our measurement.