The effect of quasar redshift errors on Lyman-α forest correlation functions

Samantha Youles, Julian E. Bautista, Andreu Font-Ribera, David Bacon, James Rich, David Brooks, Tamara M. Davis, Kyle Dawson, Govinda Dhungana, Peter Doel, Kevin Fanning, Enrique Gaztañaga, Satya Gontcho A Gontcho, Alma X. Gonzalez-Morales, Julien Guy, Klaus Honscheid, Vid Iršič, Robert Kehoe, David Kirkby, Theodore KisnerMartin Landriau, Laurent Le Guillou, Michael E. Levi, Axel de la Macorra, Paul Martini, Andrea Muñoz-Gutiérrez, Nathalie Palanque-Delabrouille, Ignasi Pérez-Ràfols, Claire Poppett, César Ramírez-Pérez, Michael Schubnell, Gregory Tarlé, Michael Walther

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Using synthetic Lyman-α forests from the Dark Energy Spectroscopic Instrument (DESI) survey, we present a study of the impact of errors in the estimation of quasar redshift on the Lyman-α correlation functions. Estimates of quasar redshift have large uncertainties of a few hundred km s−1 due to the broadness of the emission lines and the intrinsic shifts from other emission lines. We inject Gaussian random redshift errors into the mock quasar catalogues, and measure the auto-correlation and the Lyman-α-quasar cross-correlation functions. We find a smearing of the BAO feature in the radial direction, but changes in the peak position are negligible. However, we see a significant unphysical correlation for small separations transverse to the line of sight which increases with the amplitude of the redshift errors. We interpret this contamination as a result of the broadening of emission lines in the measured mean continuum, caused by quasar redshift errors, combined with the unrealistically strong clustering of the simulated quasars on small scales.
Original languageEnglish
Pages (from-to)421–433
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
Early online date29 Jul 2022
Publication statusPublished - 1 Oct 2022


  • astro-ph.CO
  • large-scale structure of Universe
  • cosmology: theory
  • UKRI
  • STFC


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