Analytic compression of EFT parameters for Lyα forest P1D via Fisher matrix and linearization allows efficient marginalization, saturating constraints with linear bias plus five effective terms and forecasting 10% and 2% precision on Δ²_p and n_p at k_p=0.7 Mpc^{-1}.
Toward a Measurement of the Cosmological Geometry at z~2: Predicting Lyman-alpha Forest Correlation in Three Dimensions, and the Potential of Future Data Sets
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abstract
The correlation between Lyman-alpha absorption in the spectra of quasar pairs can be used to measure the transverse distance scale at z~2, which is sensitive to the cosmological constant (Omega_Lambda) or other forms of vacuum energy. Using Hydro-PM simulations, I compute the three-dimensional power spectrum of the Lyman-alpha forest flux, P_F(k,mu), from which the redshift-space anisotropy of the correlation can be obtained. I find that box size ~40 Mpc/h and resolution ~40 Kpc/h are necessary for convergence of the calculations to <5% on all relevant scales, although somewhat poorer resolution can be used for large scales. I compute directly the linear theory bias parameters of the Lyman-alpha forest, potentially allowing simulation results to be extended to arbitrarily large scales. I investigate the dependence of P_F(k,mu) on the primordial power spectrum, the temperature-density relation of the gas, and the mean flux decrement, finding that the redshift-space anisotropy is relatively insensitive to these parameters. A table of results is provided for different parameter variations. I investigate the constraint that can be obtained on Omega_Lambda using quasars from a large survey. Assuming 13 (theta/1')^2 pairs at separation <theta, and including separations <10', a measurement to <5% can be made if simulations can predict the redshift-space anisotropy with <5% accuracy, or to <10% if the anisotropy must be measured from the data. The Sloan Digital Sky Survey (SDSS) will obtain spectra for a factor ~5 fewer pairs than this, so followup observations of fainter pair candidates will be necessary. I discuss the requirements on spectral resolution and signal-to-noise ratio (SDSS-quality spectra are sufficient).
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representative citing papers
An EFT-based field-level forward model for the Lyman-alpha forest matches simulations at the percent level on quasi-linear scales and generates mocks for DESI and DESI-II analyses.
Using idealized synthetic data, knowing the true continuum in Lyα forest auto- and cross-correlations reduces uncertainties on the AP parameter and Ω_m by ~10%, with extension to 240 h^{-1}Mpc scales adding up to ~15% further improvement equivalent to a 40% larger survey area.
DESI measures BAO from the Lyα forest at z_eff=2.33, reporting H(z) = (239.2 ± 4.8) (147.09 Mpc/rd) km/s/Mpc and DM(z) = (5.84 ± 0.14) (rd/147.09 Mpc) Gpc.
DESI will target luminous red galaxies to z=1, emission-line galaxies to z=1.7, quasars for tracers and Ly-alpha forest at 2.1<z<3.5, plus a bright galaxy survey, to obtain more than 30 million redshifts for BAO and matter power spectrum measurements.
citing papers explorer
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Analytic compression of the effective field theory of the Lyman-alpha forest
Analytic compression of EFT parameters for Lyα forest P1D via Fisher matrix and linearization allows efficient marginalization, saturating constraints with linear bias plus five effective terms and forecasting 10% and 2% precision on Δ²_p and n_p at k_p=0.7 Mpc^{-1}.
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Lyman-Alpha Forest and its Cross-Correlation with High-Redshift Galaxies in Effective Field Theory at the Field Level
An EFT-based field-level forward model for the Lyman-alpha forest matches simulations at the percent level on quasi-linear scales and generates mocks for DESI and DESI-II analyses.
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Probing the limits of cosmological information from the Lyman-$\alpha$ forest 2-point correlation functions
Using idealized synthetic data, knowing the true continuum in Lyα forest auto- and cross-correlations reduces uncertainties on the AP parameter and Ω_m by ~10%, with extension to 240 h^{-1}Mpc scales adding up to ~15% further improvement equivalent to a 40% larger survey area.
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DESI 2024 IV: Baryon Acoustic Oscillations from the Lyman Alpha Forest
DESI measures BAO from the Lyα forest at z_eff=2.33, reporting H(z) = (239.2 ± 4.8) (147.09 Mpc/rd) km/s/Mpc and DM(z) = (5.84 ± 0.14) (rd/147.09 Mpc) Gpc.
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The DESI Experiment Part I: Science,Targeting, and Survey Design
DESI will target luminous red galaxies to z=1, emission-line galaxies to z=1.7, quasars for tracers and Ly-alpha forest at 2.1<z<3.5, plus a bright galaxy survey, to obtain more than 30 million redshifts for BAO and matter power spectrum measurements.