Optimal data compression for Lyman-α forest cosmology

Francesca Gerardi, Andrei Cuceu, Benjamin Joachimi, Seshadri Nadathur, Andreu Font-Ribera

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The Lyman-α (Lyα) three-dimensional correlation functions have been widely used to perform cosmological inference using the baryon acoustic oscillation (BAO) scale. While the traditional inference approach employs a data vector with several thousand data points, we apply near-maximal score compression down to tens of compressed data elements. We show that carefully constructed additional data beyond those linked to each inferred model parameter are required to preserve meaningful goodness-of-fit tests that guard against unknown systematics, and to avoid information loss due to non-linear parameter dependencies. We demonstrate, on suites of realistic mocks and DR16 data from the Extended Baryon Oscillation Spectroscopic Survey, that our compression framework is lossless and unbiased, yielding a posterior that is indistinguishable from that of the traditional analysis. As a showcase, we investigate the impact of a covariance matrix estimated from a limited number of mocks, which is only well-conditioned in compressed space.
Original languageEnglish
JournalMonthly Notices of the Royal Astronomical Society
Early online date10 Jan 2024
Publication statusEarly online - 10 Jan 2024


  • astro-ph.CO
  • cosmological parameters
  • large-scale structure of universe
  • methods: data analysis
  • UKRI
  • STFC
  • ST/V000780/1
  • ST/T005009/2

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