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      Impact of Systematic Redshift Errors on the Cross-correlation of the Lyman-\(\alpha\) Forest with Quasars at Small Scales Using DESI Early Data

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          Abstract

          The Dark Energy Spectroscopic Instrument (DESI) will measure millions of quasar spectra by the end of its 5 year survey. Quasar redshift errors impact the shape of the Lyman-\(\alpha\) forest correlation functions, which can affect cosmological analyses and therefore cosmological interpretations. Using data from the DESI Early Data Release and the first two months of the main survey, we measure the systematic redshift error from an offset in the cross-correlation of the Lyman-\(\alpha\) forest with quasars. We find evidence for a redshift dependent bias causing redshifts to be underestimated with increasing redshift, stemming from improper modeling of the Lyman-\(\alpha\) optical depth in the templates used for redshift estimation. New templates were derived for the DESI Year 1 quasar sample at \(z > 1.6\) and we found the redshift dependent bias, \(\Delta r_\parallel\), increased from \(-1.94 \pm 0.15\) \(h^{-1}\) Mpc to \(-0.08 \pm 0.04\) \(h^{-1}\) Mpc (\(-205 \pm 15~\text{km s}^{-1}\) to \(-9.0 \pm 4.0~\text{km s}^{-1}\)). These new templates will be used to provide redshifts for the DESI Year 1 quasar sample.

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          Author and article information

          Journal
          27 February 2024
          Article
          2402.18009
          949b3ddc-480c-49f6-b083-618e978ec175

          http://creativecommons.org/licenses/by/4.0/

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          Custom metadata
          28 pages, 9 figures, 5 tables
          astro-ph.CO

          Cosmology & Extragalactic astrophysics
          Cosmology & Extragalactic astrophysics

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