A consistent and robust measurement of the thermal state of the IGM at $2 \leq z \leq 4$ from a large sample of Ly$α$ forest spectra: Evidence for late and rapid HeII reionization

Gaikwad, Prakash; Srianand, Raghunathan; Haehnelt, Martin G.; Choudhury, Tirthankar Roy

doi:10.48550/arxiv.2009.00016

Cited by 15 publications

(45 citation statements)

References 76 publications

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“…The ionization of helium leads to a second increase of the temperature until He II is fully ionized (z 3), resulting in a second peak of T 0 1.4 × 10 4 K. The second peak is followed by a second period of cooling from cosmic expansion. Our result is consistent with previous estimates from Gaikwad et al (2020b) and Gaikwad et al (2020a),…”

Section: Discussionsupporting

confidence: 94%

“…Our model predicts that T 0 increases monotonically until He II reionization completes at z ∼ 3, resulting in a second peak in the temperature (T 0 1.4 × 10 4 K) followed by a second epoch of cooling due to cosmic expansion. Our results for the evolution of T 0 during z 4.5 are consistent with the determinations from Gaikwad et al (2020a) and Walther et al (2019) that show a similar T 0 history within the uncertainties during and after He II reionization, as both show a peak in T 0 at z ∼ 2.8 − 3.0. Our T 0 (z) results are higher yet consistent within the uncertainties from the measurement by Bolton et al (2014) at z = 2.4.…”

Section: Evolution Of the Igm Temperaturesupporting

confidence: 90%

“…After helium reionization cooling from cosmic expansion causes an increase on γ for a second time. The evolution of the power-law index in our model is consistent with measurements from Hiss et al (2018), Boera et al (2019), Gaikwad et al (2020b), andGaikwad et al (2020a), and shows deviations only for a few redshift bins after He II reionization completes. The transition in γ after He II reionization in our model is not as pronounced as the determinations from Gaikwad et al (2020a) and Hiss et al (2018).…”

Section: Evolution Of the Igm Temperaturesupporting

confidence: 83%

“…We emphasize that our approach differs from previous studies of the thermal history of the IGM (e.g., Bolton et al 2014;Nasir et al 2016;Hiss et al 2018;Boera et al 2019;Walther et al 2019;Gaikwad et al 2020a) in an important aspect. Typically, the method adopted to infer the thermal state of the IGM from observations of the Lyman-α forest involves marginalizing over the thermal parameters T 0 and γ in the approximate powerlaw density-temperature relation (Hui & Gnedin 1997) T (∆) = T 0 ∆ γ−1 , where ∆ = ρ gas /ρ is the gas overdensity.…”

Section: Inference Of the Uvb Modelmentioning

confidence: 93%

“…Since the properties of the gas at one redshift cannot be disentangled from its properties at previous epochs and the thermal and ionization structure of the IGM evolve with cosmic time along continuous trajectories, the marginalization over the parameter posterior distributions should not be performed independently at each redshift (cf. Bolton et al 2014;Nasir et al 2016;Hiss et al 2018;Boera et al 2019;Walther et al 2019;Gaikwad et al 2020a).…”

Section: Introductionmentioning

confidence: 99%

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

Villasenor,

Robertson,

Madau

et al. 2021

Preprint

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The filamentary network of intergalactic medium (IGM) gas that gives origin to the Lyman-α 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 highresolution 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-α 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-α 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 R ≈ 6.1 with a first IGM temperature peak T 0 1.3 × 10 4 K, and is followed by the reionization of He II that completes by z R ≈ 3.0 and yields a second temperature peak of T 0 1.4 × 10 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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Section: Discussionsupporting

confidence: 94%

Section: Evolution Of the Igm Temperaturesupporting

confidence: 90%

Section: Evolution Of the Igm Temperaturesupporting

confidence: 83%

Section: Inference Of the Uvb Modelmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

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

Villasenor,

Robertson,

Madau

et al. 2021

Preprint

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Neutrino mass bounds from confronting an effective model with BOSS Lyman-α data

Garny

Konstandin

Sagunski

et al. 2021

J. Cosmol. Astropart. Phys.

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We present an effective model for the one-dimensional Lyman-α flux power spectrum far above the baryonic Jeans scale. The main new ingredient is constituted by a set of two parameters that encode the impact of small, highly non-linear scales on the one-dimensional power spectrum on large scales, where it is measured by BOSS. We show that, by marginalizing over the model parameters that capture the impact of the intergalactic medium, the flux power spectrum from both simulations and observations can be described with high precision. The model displays a degeneracy between the neutrino masses and the (unknown, in our formalism) normalization of the flux power spectrum. This degeneracy can be lifted by calibrating one of the model parameters with simulation data, and using input from Planck CMB data. We demonstrate that this approach can be used to extract bounds on the sum of neutrino masses with comparably low numerical effort, while allowing for a conservative treatment of uncertainties from the dynamics of the intergalactic medium. An explorative analysis yields an upper bound of 0.16eV at 95% C.L. when applied to BOSS data at 3 ≤ z ≤ 4.2. We also forecast that if the systematic and statistical errors will be reduced by a factor two the upper bound will become 0.1eV at 95% C.L, and 0.056eV when assuming a 1% error.

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Simulating intergalactic gas for DESI-like small scale Lymanα forest observations

Walther

Armengaud

Ravoux

et al. 2021

J. Cosmol. Astropart. Phys.

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Measurements of the Lyα forest based on large numbers of quasar spectra from sky surveys such as SDSS/eBOSS accurately probe the distribution of matter on small scales and thus provide important constraints on several ingredients of the cosmological model. A main summary statistic derived from those measurements is the one-dimensional power spectrum, P1D, of the Lyα absorption. However, model predictions for P1D rely on expensive hydrodynamical simulations of the intergalactic medium, which was the limiting factor in previous analyses. Datasets from upcoming surveys such as DESI will push observational accuracy near the 1%-level and probe even smaller scales. This observational push mandates even more accurate simulations as well as more careful exploration of parameter space. In this work we evaluate the robustness and accuracy of simulations and the statistical framework used to constrain cosmological parameters. We present a comparison between the grid-based simulation code Nyx and SPH-based code Gadget in the context of P1D. In addition, we perform resolution and box-size convergence tests using Nyx code. We use a Gaussian process emulation scheme to reduce the number of simulations required for exploration of parameter space without sacrificing the model accuracy. We demonstrate the ability to produce unbiased parameter constraints in an end-to-end inference test using mock eBOSS- and DESI-like data, and we advocate for the usage of adaptive sampling schemes as opposed to using a fixed Latin hypercube design.

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A consistent and robust measurement of the thermal state of the IGM at $2 \leq z \leq 4$ from a large sample of Ly$α$ forest spectra: Evidence for late and rapid HeII reionization

Cited by 15 publications

References 76 publications

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

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

Neutrino mass bounds from confronting an effective model with BOSS Lyman-α data

Simulating intergalactic gas for DESI-like small scale Lymanα forest observations

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