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Inferring the Thermal History of the Intergalactic Medium from the Properties of the Hydrogen and Helium Lyman-alpha Forest

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arxiv 2111.00019 v3 pith:EEMMW5AA submitted 2021-10-29 astro-ph.CO

classification astro-ph.CO
keywords hydrogenheliumlyman-alphaforestintergalacticrangereionizationspectra
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The filamentary network of intergalactic medium (IGM) gas that gives origin to the Lyman-alpha forest in the spectra of distant quasars encodes information on the physics of structure formation and the early thermodynamics of diffuse baryonic material. Here, we use a massive suite of more than 400 high-resolution cosmological hydrodynamical simulations run with the Graphics Processing Unit-accelerated code Cholla to study the IGM at high spatial resolution maintained over the entire computational volume. The simulations capture a wide range of possible thermal histories of intergalactic gas by varying the amplitude and timing of the photoheating and photoionizing background produced by star-forming galaxies and active galactic nuclei. A statistical comparison of synthetic spectra with the observed 1D flux power spectra of hydrogen in 14 redshift bins over the full range 2.2 <= z <= 5.0 and with the Lyman-alpha opacity of helium in 5 redshift bins over the range 2.4 < z < 2.9 tightly constrains the photoionization and photoheating history of the IGM. By leveraging the constraining power of the available Lyman-alpha forest data to break model degeneracies, we find that the IGM experienced two main reheating events from the non-equilibrium ionization of hydrogen and helium over 1.2 Gyr of cosmic time. For our best-fit model, hydrogen reionization completes by z~6.0 with a first IGM temperature peak T_0 ~ 1.3x10^4 K, and is followed by the reionization of HeII that completes by z~3.0 and yields a second temperature peak of T_0 ~ 1.4x10^4 K. We discuss how our results can be used to obtain information on the timing and the sources of hydrogen and helium reionization.

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Cited by 6 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. Modeling the Cosmological Lyman-$\alpha$ Forest at the Field Level

    astro-ph.CO 2025-06 conditional novelty 7.0 of 10

    An effective-field-theory forward model reproduces the Lyman-alpha forest field from a hydrodynamic simulation at percent level, down to a few megaparsecs, using the same initial conditions.

  2. Ringing of the Reionization: A first direct measurement of the intergalactic pressure smoothing scale at redshift z>4.2 as imprinted onto small-scale peculiar velocities in the Lyman-alpha forest

    astro-ph.CO 2026-07 reject novelty 6.0 of 10

    A claimed first direct measurement of the IGM pressure smoothing scale at z≈4.2–5.0 from a fitted peak in the Lyman-alpha flux power spectrum, tied to an acoustic feature in the peculiar velocity gradient.

  3. Bridging Simulations and EFT: A Hybrid Model of the Lyman-Alpha Forest Field

    astro-ph.CO 2025-12 conditional novelty 6.0 of 10

    A hybrid EFT forward model using N-body displacements reproduces the simulated Lyman-alpha forest to 5% at k <= 1 h/Mpc with a white-noise residual.

  4. The Compressed 3D Lyman-Alpha Forest Bispectrum

    astro-ph.CO 2025-10 conditional novelty 6.0 of 10

    The Lyman-alpha forest bispectrum can be compressed into 26 skew spectra, including a new shifted variant, with tree-level EFT predictions matching simulations at 1-2 sigma up to k≈0.17 h/Mpc.

  5. Small-scale Lyman alpha forest cosmology with PRIYA: Constraints from XQ100 and KODIAQ-SQUAD one-dimensional flux power spectra

    astro-ph.CO 2025-09 conditional novelty 6.0 of 10

    The XQ100 Lyman-alpha forest power spectrum, modeled with the PRIYA simulations, gives cosmological constraints consistent with eBOSS and Planck and constrains the IGM thermal history without external temperature data...

  6. Patchy Helium and Hydrogen Reionization from the Kinetic Sunyaev-Zel'dovich Effect and Galaxies

    astro-ph.CO 2025-06 conditional novelty 6.0 of 10

    Forecasts show that cross-correlating kSZ temperature-squared maps with galaxy-reconstructed velocity-squared maps can jointly constrain hydrogen and helium reionization, making helium measurable with CMB-HD and MegaMapper.

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