DESI DR2 BAO data exhibits 2.3 sigma tension with CMB in Lambda-CDM but prefers evolving dark energy (w0 > -1, wa < 0) at 3.1 sigma with CMB and 2.8-4.2 sigma when including supernovae.
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Dark energy and curvature from a future baryonic acoustic oscillation survey using the Lyman-alpha forest
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abstract
We explore the requirements for a Lyman-alpha forest (LyaF) survey designed to measure the angular diameter distance and Hubble parameter at 2~<z~<4 using the standard ruler provided by baryonic acoustic oscillations (BAO). The goal would be to obtain a high enough density of sources to probe the three-dimensional density field on the scale of the BAO feature. A percent-level measurement in this redshift range can almost double the Dark Energy Task Force Figure of Merit, relative to the case with only a similar precision measurement at z~1, if the Universe is not assumed to be flat. This improvement is greater than the one obtained by doubling the size of the z~1 survey, with Planck and a weak SDSS-like z=0.3 BAO measurement assumed in each case. Galaxy BAO surveys at z~1 may be able to make an effective LyaF measurement simultaneously at minimal added cost, because the required number density of quasars is relatively small. We discuss the constraining power as a function of area, magnitude limit (density of quasars), resolution, and signal-to-noise of the spectra. For example, a survey covering 2000 sq. deg. and achieving S/N=1.8 per Ang. at g=23 (~40 quasars per sq. deg.) with an R~>250 spectrograph is sufficient to measure both the radial and transverse oscillation scales to 1.4% from the LyaF (or better, if fainter magnitudes and possibly Lyman-break galaxies can be used). At fixed integration time and in the sky-noise-dominated limit, a wider, noisier survey is generally more efficient; the only fundamental upper limit on noise being the need to identify a quasar and find a redshift. Because the LyaF is much closer to linear and generally better understood than galaxies, systematic errors are even less likely to be a problem.
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First-year DESI BAO data are consistent with flat LambdaCDM and, when combined with CMB, show a 2.5-3.9 sigma preference for evolving dark energy (w0 > -1, wa < 0) that strengthens with certain supernova datasets.
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.
DESI DR2 delivers 0.65% precision BAO measurements from the LyA forest at z_eff=2.33, with D_H/r_d = 8.632 ± 0.098 ± 0.026 and D_M/r_d = 38.99 ± 0.52 ± 0.12.
Fisher forecasts indicate that Lyα-21cm cross-spectra with PUMA and CMB data can improve constraints on neutrino self-interaction strength G_eff by 1-2 orders of magnitude over CMB alone.
Forecasts show DESI-like and SKA1-Mid observations could constrain primordial magnetic field amplitude and spectral index to roughly 10% precision via 21cm auto-spectrum and Lyα-21cm cross-spectrum.
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.
Fisher forecasts indicate joint post-reionization LSS cross-spectra and CMB-S4-like data can reach O(10^{-4}) uncertainty on ultra-light axion fraction for m_a ≲ 10^{-28} eV, with peak sensitivity near 10^{-25} eV.
citing papers explorer
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DESI DR2 Results II: Measurements of Baryon Acoustic Oscillations and Cosmological Constraints
DESI DR2 BAO data exhibits 2.3 sigma tension with CMB in Lambda-CDM but prefers evolving dark energy (w0 > -1, wa < 0) at 3.1 sigma with CMB and 2.8-4.2 sigma when including supernovae.
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DESI 2024 VI: Cosmological Constraints from the Measurements of Baryon Acoustic Oscillations
First-year DESI BAO data are consistent with flat LambdaCDM and, when combined with CMB, show a 2.5-3.9 sigma preference for evolving dark energy (w0 > -1, wa < 0) that strengthens with certain supernova datasets.
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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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DESI DR2 Results I: Baryon Acoustic Oscillations from the Lyman Alpha Forest
DESI DR2 delivers 0.65% precision BAO measurements from the LyA forest at z_eff=2.33, with D_H/r_d = 8.632 ± 0.098 ± 0.026 and D_M/r_d = 38.99 ± 0.52 ± 0.12.
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Neutrino self-interactions in post-reionization era: Lyman-$\alpha$, 21-cm and cross-spectra
Fisher forecasts indicate that Lyα-21cm cross-spectra with PUMA and CMB data can improve constraints on neutrino self-interaction strength G_eff by 1-2 orders of magnitude over CMB alone.
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Primordial magnetic fields in the light of upcoming post-EoR Lyman-$\alpha$ and 21-cm observations
Forecasts show DESI-like and SKA1-Mid observations could constrain primordial magnetic field amplitude and spectral index to roughly 10% precision via 21cm auto-spectrum and Lyα-21cm cross-spectrum.
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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.
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Tracing Ultra Light Axions in Post-reionization, Lyman-$\alpha$ and CMB Missions
Fisher forecasts indicate joint post-reionization LSS cross-spectra and CMB-S4-like data can reach O(10^{-4}) uncertainty on ultra-light axion fraction for m_a ≲ 10^{-28} eV, with peak sensitivity near 10^{-25} eV.