Optimal 1D Ly α forest power spectrum estimation - II. KODIAQ, SQUAD, and XQ-100

Naim Göksel Karaçayll, Nikhil Padmanabhan, Andreu Font-Ribera, Vid Iršič, Michael Walther, David Brooks, Enrique Gaztañaga, Robert Kehoe, Michael Levi, Pierros Ntelis, Nathalie Palanque-Delabrouille, Gregory Tarlé

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We measure the 1D Ly α power spectrum P1D from Keck Observatory Database of Ionized Absorption toward Quasars (KODIAQ), The Spectral Quasar Absorption Database (SQUAD), and XQ-100 quasars using the optimal quadratic estimator. We combine KODIAQ and SQUAD at the spectrum level, but perfo a separate XQ-100 estimation to control its large resolution corrections in check. Our final analysis measures P1D at scales k < 0.1 s km-1 between redshifts $z$ = 2.0-4.6 using 538 quasars. This sample provides the largest number of high-resolution, high-S/N observations; and combined with the power of optimal estimator it provides exceptional precision at small scales. These small-scale modes (k 0.02 s km-1), unavailable in Sloan Digital Sky Survey and Dark Energy Spectroscopic Instrument analyses, are sensitive to the theal state and reionization history of the intergalactic medium, as well as the nature of dark matter. As an example, a simple Fisher forecast analysis estimates that our results can improve small-scale cut-off sensitivity by more than a factor of 2.

Original languageEnglish
Pages (from-to)2842-2855
Number of pages14
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Early online date11 Nov 2021
Publication statusPublished - 1 Jan 2022


  • absorption lines
  • data analysis
  • intergalactic medium
  • methods
  • quasars
  • UKRI
  • STFC

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