The Dark Energy Spectroscopic Instrument: Simulations of the first year Lyman-α quasars observations

Abstract

The Baryon Acoustic Oscillations (BAO) provide a standard ruler to probe cosmology. In recent years there have been many projects dedicated to study BAO. The first of the next generation of these projects will be the Dark Energy Spectroscopic instrument (DESI), dedicated to the study of the ejects of Dark Energy on the cosmic expansion history by studying BAO and Redshift Space Distortions. DESI will measure the spectra of nearly 30 million galaxies distributed in a 14,000 deg2 area in a five-year period, including 0.7 million quasars at a redshift z > 2.1, that include a collection of absorption lines with in their spectra, known as the Lyman-α forest. This work develops a straight forward pipeline to simulate the observations of the Lyman-α quasars during the first year of DESI’s operations. Including the simulation of the scheduling of the survey, the selection of mock targets that fulfill DESI’s requirements, the assignment of the instrument fibers to observe these targets, the simulation of the Lyman-α quasar spectra and finally the measurement of the correlation function. With this pipeline a realization of DESI’s first year footprint was obtained, however the actual DESI footprint will depend on the weather presented during the year. Concerning the simulation of the Lyman-α quasars spectra this work makes its strongest contribution to the DESI collaboration by providing a modification of the script dedicated to this task, quick quasars, this modification includes the feature to of simulating a given footprint with different quasar densities and with multiple exposure times. With the modified version of quick quasars, two simulations of Lyman-α quasars were produced, one where all the quasars in the footprint have a single exposure, and another where there are multiple exposure times. The error bars of the correlation function of these realizations were compared obtaining a improvement of ~ 20% and ~ 10% in the auto-correlation and cross-correlation, respectively.