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Abstract We present new cosmological parameter constraints from the eBOSS Lyman-α forest survey. We use a new theoretical model and likelihood based on the PRIYA simulation suite. PRIYA is the first suite to resolve the Lyman-αforest in a (120 Mpc/h)3volume, using a multi-fidelity emulation technique. We use PRIYA to predict Lyman-αforest observables with ≲ 1% interpolation error over an 11 dimensional (9 simulated, 2 in post-processing) parameter space. We identify an internal tension within the flux power spectrum data. Once the discrepant data is removed, we find the primeval scalar spectral index measured at a pivot scale ofk0= 0.78 Mpc-1to benP= 1.009+0.027-0.018at 68% confidence. This measurement from the Lyman-αforest flux power spectrum alone is in reasonable agreement with Planck, and in tension with earlier eBOSS analyses. The amplitude of matter fluctuations isσ8= 0.733+0.026-0.029at 68% confidence, in agreement with Dark Energy Survey weak lensing measurements and other small-scale structure probes and in tension with CMB measurements from Planck and ACT. The effective optical depth to Lyman-α photons from our pipeline is in good agreement with earlier high resolution measurements. We find a linear power atz= 3 andk= 0.009 s/km of Δ2L= 0.302+0.024-0.027with a slopeneff= -2.264+0.026-0.018. Our flux power spectrum only chains prefer a low level of heating during helium reionization. When we add IGM temperature data we findnP= 0.983 ± 0.020 andσ8= 0.703+0.023-0.027. Our chains prefer an early and long helium reionization event, as suggested by measurements from the helium Lyman-αforest. In the near future we will use our pipeline to infer cosmological parameters from the DESI Lyman-α data.
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A multifidelity emulator for the Lyman-α forest flux power spectrum
ABSTRACT In this work, we extend our recently developed multifidelity emulation technique to the simulated Lyman-α forest flux power spectrum. Multifidelity emulation allows interpolation of simulation outputs between cosmological parameters using many cheap low-fidelity simulations and a few expensive high-fidelity simulations. Using a test suite of small-box (30 Mpc h−1) simulations, we show that multifidelity emulation is able to reproduce the Lyman-α forest flux power spectrum well, achieving an average accuracy when compared to a test suite of $$0.8\, {\rm {per\ cent}}$$. We further show that it has a substantially increased accuracy over single-fidelity emulators, constructed using either the high- or low-fidelity simulations only. In particular, it allows the extension of an existing simulation suite to smaller scales and higher redshifts.
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- Award ID(s):
- 1817256
- PAR ID:
- 10376582
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 517
- Issue:
- 3
- ISSN:
- 0035-8711
- Page Range / eLocation ID:
- p. 3200-3211
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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