Cosmology from clustering of Lyman-alpha galaxies: breaking non-gravitational Lyman-alpha radiative transfer degeneracies using the bispectrum

TL;DR

This paper demonstrates that using the bispectrum in Lyman-alpha galaxy surveys can break degeneracies caused by radiative transfer effects, enabling more accurate cosmological parameter estimation.

Contribution

It introduces the use of the bispectrum to distinguish gravitational effects from radiative transfer effects in LAE galaxy clustering analyses.

Findings

Bispectrum effectively breaks degeneracies in clustering measurements.

Combining power spectrum and bispectrum improves cosmological constraints.

Method enhances the precision of measuring the universe's expansion at high redshift.

Abstract

Large surveys for Lyman-alpha emitting (LAE) galaxies have been proposed as a new method for measuring clustering of the galaxy population at high redshift with the goal of determining cosmological parameters. However, Lyman-alpha radiative transfer effects may modify the observed clustering of LAE galaxies in a way that mimics gravitational effects, potentially reducing the precision of cosmological constraints. For example, the effect of the linear redshift-space distortion on the power spectrum of LAE galaxies is potentially degenerate with Lyman-alpha radiative transfer effects owing to the dependence of observed flux on intergalactic medium velocity gradients. In this paper, we show that the three-point function (bispectrum) can distinguish between gravitational and non-gravitational effects, and thus breaks these degeneracies, making it possible to recover cosmological parameters from LAE galaxy surveys. Constraints on the angular diameter distance and the Hubble expansion rate can also be improved by combining power spectrum and bispectrum measurements.