Self-Consistent Modeling of Reionization in Cosmological Hydrodynamical Simulations

Jose O\~norbe; Joseph F Hennawi; Zarija Luki\'c

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Self-Consistent Modeling of Reionization in Cosmological Hydrodynamical Simulations

Jose Oñorbe, Joseph F Hennawi, Zarija Lukić

Cosmology and Nongalactic Astrophysics · Submitted 14 Jul 2016

abstract compiled · 2026-09-23 · no language-model review

The authors' main claim The premature IGM heating we have uncovered implies that previous work has likely dramatically overestimated the impact of photoionization feedback on galaxy formation, which sets the minimum halo mass able to form stars at high redshifts.

how it is stated · hedged possibility 0.98 read the record →

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arXiv ID1607.04218 (version 2)

Pith IDXQUCVO7H, Pith's permanent record of this paper and its review

CitationJose O\~norbe, Joseph F Hennawi, Zarija Luki\'c. "Self-Consistent Modeling of Reionization in Cosmological Hydrodynamical Simulations." arXiv:1607.04218 (2016). https://pith.science/paper/XQUCVO7H

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What the abstract itself states, as probabilities: claims first 0.08 · states limitation 0.20 · human participants 0.01 · controlled comparison 0.58 · randomized assignment 0.01 · states quantitative result 0.66 · compares with prior results 0.93 · mentions code or data availability 0.94.

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The ultraviolet background (UVB) emitted by quasars and galaxies governs the ionization and thermal state of the intergalactic medium (IGM), regulates the formation of high-redshift galaxies, and is thus a key quantity for modeling cosmic reionization. The vast majority of cosmological hydrodynamical simulations implement the UVB via a set of spatially uniform photoionization and photoheating rates derived from UVB synthesis models. We show that simulations using canonical UVB rates reionize and, perhaps more importantly, spuriously heat the IGM, much earlier z ~ 15 than they should. This problem arises because at z > 6, where observational constraints are nonexistent, the UVB amplitude is far too high. We introduce a new methodology to remedy this issue, and we generate self-consistent photoionization and photoheating rates to model any chosen reionization history. Following this approach, we run a suite of hydrodynamical simulations of different reionization scenarios and explore the impact of the timing of reionization and its concomitant heat injection on the the thermal state of the IGM. We present a comprehensive study of the pressure smoothing scale of IGM gas, illustrating its dependence on the details of both hydrogen and helium reionization, and argue that it plays a fundamental role in interpreting Lyman-alpha forest statistics and the thermal evolution of the IGM. The premature IGM heating we have uncovered implies that previous work has likely dramatically overestimated the impact of photoionization feedback on galaxy formation, which sets the minimum halo mass able to form stars at high redshifts. We make our new UVB photoionization and photoheating rates publicly available for use in future simulations.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#	sentence	role	the authors' own work	states the main conclusion	strength
s0	The ultraviolet background (UVB) emitted by quasars and galaxies governs the ionization and thermal state of the intergalactic medium (IGM), regulates the formation of high-redshift galaxies, and is thus a key quantity for modeling cosmic reionization.	background 1.00	0.05	0.04	asserted 1.00
s1	The vast majority of cosmological hydrodynamical simulations implement the UVB via a set of spatially uniform photoionization and photoheating rates derived from UVB synthesis models.	background 1.00	0.06	0.03	asserted 1.00
s2	We show that simulations using canonical UVB rates reionize and, perhaps more importantly, spuriously heat the IGM, much earlier z ~ 15 than they should.	result 0.99	0.91	0.46	asserted 0.97
s3	This problem arises because at z > 6, where observational constraints are nonexistent, the UVB amplitude is far too high.	interpretation 0.66	0.48	0.11	asserted 1.00
s4	We introduce a new methodology to remedy this issue, and we generate self-consistent photoionization and photoheating rates to model any chosen reionization history.	method 0.55	0.95	0.09	asserted 1.00
s5	Following this approach, we run a suite of hydrodynamical simulations of different reionization scenarios and explore the impact of the timing of reionization and its concomitant heat injection on the the thermal state of the IGM.	method 0.69	0.96	0.06	asserted 0.84
s6	We present a comprehensive study of the pressure smoothing scale of IGM gas, illustrating its dependence on the details of both hydrogen and helium reionization, and argue that it plays a fundamental role in interpreting Lyman-alpha forest statistics and the thermal evolution of the IGM.	contribution 0.52	0.93	0.17	asserted 0.99
s7	The premature IGM heating we have uncovered implies that previous work has likely dramatically overestimated the impact of photoionization feedback on galaxy formation, which sets the minimum halo mass able to form stars at high redshifts.	interpretation 1.00	0.65	0.36	hedged possibility 0.98
s8	We make our new UVB photoionization and photoheating rates publicly available for use in future simulations.	contribution 0.74	0.89	0.03	asserted 0.97

What kind of paper the classifier reports this is: method or tool 0.69 · evidence from simulation or computation 1.00.

What was examined, and what was not

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arXiv listing abstract v2

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full text
figures and tables
references and citing sentences
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The paper

Original abstract

The ultraviolet background (UVB) emitted by quasars and galaxies governs the ionization and thermal state of the intergalactic medium (IGM), regulates the formation of high-redshift galaxies, and is thus a key quantity for modeling cosmic reionization. The vast majority of cosmological hydrodynamical simulations implement the UVB via a set of spatially uniform photoionization and photoheating rates derived from UVB synthesis models. We show that simulations using canonical UVB rates reionize and, perhaps more importantly, spuriously heat the IGM, much earlier z ~ 15 than they should. This problem arises because at z > 6, where observational constraints are nonexistent, the UVB amplitude is far too high. We introduce a new methodology to remedy this issue, and we generate self-consistent photoionization and photoheating rates to model any chosen reionization history. Following this approach, we run a suite of hydrodynamical simulations of different reionization scenarios and explore the impact of the timing of reionization and its concomitant heat injection on the the thermal state of the IGM. We present a comprehensive study of the pressure smoothing scale of IGM gas, illustrating its dependence on the details of both hydrogen and helium reionization, and argue that it plays a fundamental role in interpreting Lyman-alpha forest statistics and the thermal evolution of the IGM. The premature IGM heating we have uncovered implies that previous work has likely dramatically overestimated the impact of photoionization feedback on galaxy formation, which sets the minimum halo mass able to form stars at high redshifts. We make our new UVB photoionization and photoheating rates publicly available for use in future simulations.

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References

Forward citations

Cited by 8 Pith papers

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

Strongest constraints on dark acoustic oscillations from the Lyman-alpha forest
astro-ph.CO 2026-06 unverdicted novelty 7.0 of 10

First constraints from Ly-alpha forest limit DAO participation to at most 30% of dark matter for peaks below 50 h/Mpc at 95% CL using a deep kernel emulator of simulations.
specwizard: A Public Python Framework for Creating Synthetic Absorption Spectra from Hydrodynamical Simulations
astro-ph.CO 2026-10 accept novelty 6.0 of 10

specwizard is a publicly available Python framework that produces synthetic quasar absorption spectra from simulations, validated against Lyman-alpha forest observations.
Resolving the physics of Quasar Ly$\alpha$ Nebulae (RePhyNe): II. The dense and clumpy CGM of Quasars at $z \sim$ 3.5
astro-ph.GA 2026-10 conditional novelty 6.0 of 10

Simulations underpredict the dense, clumpy cold circumgalactic gas that powers quasar nebulae, requiring densities above 10 cm^-3 and clumping factors several times larger than simulated.
3D matter power spectrum correspondence to 1D Lyman-alpha flux power spectrum
astro-ph.CO 2025-05 conditional novelty 6.0 of 10

A phenomenological recipe maps 3D matter power to 1D Lyman-alpha flux power, adds warm dark matter and pressure cutoffs in quadrature, and matches simulations to within 5-20%.
New limits on light dark matter - proton cross section from the cosmic large-scale structure
astro-ph.CO 2021-11 conditional novelty 6.0 of 10

Lyman-alpha forest data combined with a simulation emulator exclude dark matter-proton cross sections above roughly 6e-30 cm^2 at 95% credibility for a 100 keV dark matter particle, improving prior cosmological bounds...

Show 3 more citing papers

Lyman-$\alpha$ forest constraints on pure and mixed fuzzy dark matter
astro-ph.CO 2026-06 unverdicted novelty 5.0 of 10

Lyman-alpha forest data yield m_FDM > 1.9e-21 eV (95% CL) for pure FDM and f_FDM upper limits of 0.07-0.65 for mixed FDM at log10(m_FDM/eV) = -23 to -21.
Strong bound on canonical ultra-light axion dark matter from the Lyman-alpha forest
astro-ph.CO 2020-07 conditional novelty 5.0 of 10

Lyman-alpha forest data exclude ultra-light axion dark matter below 2e-20 eV at 95% credibility, ruling out the canonical 1e-22 to 1e-21 eV window.
How to constrain warm dark matter with the Lyman $\alpha$ forest
astro-ph.CO 2019-12 conditional novelty 5.0 of 10

With a deliberately cold reionization history that minimizes pressure smoothing, the Lyman-alpha forest still excludes thermal-relic warm dark matter below 1.9 keV at 95% confidence.

How later papers used it

77 later papers cite it

Evidence: substantial. 53 of the citing papers share no author with it, and 24 of those carry a confident label from Pith's citation classifier.

Pith read 23 of the 128 citing sentences, choosing only those whose citation markers point at this paper alone, and wrote the paraphrases from them. The summary, the counts, the evidence level, the links and the quotes come from code; the summary counts the papers listed below. A later paper is listed under a label when Pith's citation classifier gives one of its sentences that label at probability 0.8 or more (0.95 for support), Pith's reading finds that the citing paper itself did it, and a second check confirms the paraphrase against the sentence. This section lists uses only. It does not list criticism or disagreement, so their absence here says nothing about how the paper has been received. Papers that share an author with this one are listed apart, under "By the same authors". A quote is the citing authors' own sentence, shown when their paper's licence is CC BY, CC BY-SA or CC0. JSON

6 later papers by other authors are listed below: 4 used its method or tool, 1 used its data or values and 1 compared its own results with it. 2 more papers by the same authors are listed: 1 used its method or tool and 1 used its data or values.

Uses its method or tool 5 of 16 papers with this label · 1 by the same authors

Employed the reionization model of this paper to vary the redshift dependence.

General framework for cosmological dark matter bounds using $N$-body simulations (2020) · 0.98 · paraphrased: the licence does not allow quoting
Used an improved treatment of the IGM opacity from this paper that consistently captures the transition from a neutral to ionised IGM.

The effect of inhomogeneous reionisation on the Lyman-$\alpha$ forest power spectrum at redshift $z>4$: implications for thermal parameter recovery (2021) · 0.93 · paraphrased: the licence does not allow quoting
Varied the mid-point redshift of hydrogen reionization and the total heat injection during reionization according to the model of this paper.

Strong bound on canonical ultra-light axion dark matter from the Lyman-alpha forest (2020) · 0.96 · paraphrased: the licence does not allow quoting
Varied the input ionization and heating rates by the model of this paper to vary the thermal IGM parameters.

New limits on light dark matter - proton cross section from the cosmic large-scale structure (2021) · 0.92 · paraphrased: the licence does not allow quoting

By the same authors

Used the methodology of this paper to simulate reionization models, varying the timing and duration of reionization and its associated heat injection.

Constraining Reionization with the $z \sim 5-6$ Lyman-$\alpha$ Forest Power Spectrum: the Outlook after Planck (2017) (same authors) · 1.00 · paraphrased: the licence does not allow quoting

Uses its data or values 2 of 4 papers with this label · 1 by the same authors

To reach this goal, we used the set of simulated skewers at redshift $z = 1.8$ from the THERMAL (Thermal History and Evolution in Reionization Models of Absorption Lines) [thermal.joseonorbe.com] suite [ref] .

Thermal state of the intergalactic medium near to the optical limit for the Ly-$\alpha$ forest (2021) · Simulations · 0.88

By the same authors

The mean photoionization rate is rescaled to match the observed effective Ly$α$ optical depth $τ_eff=0.00126×e^3.294√(z)$ [ref] , but the thermal structure is kept unchanged from the original simulation output.

Photometric IGM Tomography: Efficiently Mapping Quasar Light Echoes with Deep Narrow Band Imaging (2022) (same authors) · Cosmological hydrodynamic simulation · 0.90

Compares with it 1 of 6 papers with this label

Reported that its own simulation predicts a temperature T0 of about 7700 K at redshifts 5.0 and 5.4, also in agreement with findings of this paper.

The Lyman-$\alpha$ forest as a diagnostic of the nature of the dark matter (2018) · 0.87 · paraphrased: the licence does not allow quoting

How the literature uses it

20 arXiv papers cite this in 44 sentences

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers citing it · 24 sentences without a confident label

Uses its method or tool 9 papers

In order to simulate each reionization model discussed here we have used the methodology presented in [ref] , which allows us to vary the timing and duration of reionization, and its associated heat injection, enabling us to simulate a diverse range of reionization histories.

Constraining Reionization with the $z \sim 5-6$ Lyman-$\alpha$ Forest Power Spectrum: the Outlook after Planck · Simulating Reionization Histories in Light of New Planck Constraints · 1.00
Therefore, in this work we suggest the following procedure for obtaining robust Lyman-$α$ forest bounds: [(1)] * In order to minimise the pressure effects, we run hydrodynamical simulations with model of ultraviolet background (UVB) LateCold from [ref] .[The details about the numerical simulations can be found in [ref] .] In this model the reionization starts at redshift $z=6.7$, later than other thermal histories, considered in [ref] or by other groups.

How to constrain warm dark matter with the Lyman $\alpha$ forest · Introduction · 0.81
In order to vary the redshift dependence, we employ the reionization model of Ref. [ref] .

General framework for cosmological dark matter bounds using $N$-body simulations · Simulation input and output · 0.98

Uses its data or values 1 paper

By construction it gives the minimal filaments size.[We thank J. Onorbe for sharing with us the data of the LateCold thermal history that were not published together with the other thermal histories in [ref] . hi photo-heating and photo-ionization rates are shown in Fig. [ref].] We have assumed that the intergalactic medium is optically thin, and that reionization happens uniformly in all the space. * We explicitly marginalise over the IGM temperature (Doppler broadening) adding their effects to the FPS in post-processing.

How to constrain warm dark matter with the Lyman $\alpha$ forest · Introduction · 0.87

Cites it as support 2 papers

This is because both the cooling and dynamical times in the rarefied IGM are long, comparable to the Hubble time and therefore memory of $$ reionization is retained [ref] .

Constraining Reionization with the $z \sim 5-6$ Lyman-$\alpha$ Forest Power Spectrum: the Outlook after Planck · Conclusions · 0.98
Fortunately, the absence of coupling between the radiative transfer and the hydrodynamic response to reionization heating is unlikely to affect the calibration of the simulation to the forest data [ref] as the pressure smoothing scale at redshifts $z>5$ for our chosen UV background is less than $100h^-1 ckpc$ [ref] , approximately equal to the cell size of our grid (described below).

Revised estimates of CMB $B$-mode polarization induced by patchy reionization · Reionization model calibrated to Lyman-Lg forest data · 0.97

Cites it as background 3 papers

In an expanding universe with an evolving thermal state at a given epoch, this scale depends on the entire thermal history of IGM because fluctuations at earlier times expand or fail to collapse depending on the IGM temperature at that epoch [ref] .

Constraining Reionization with the $z \sim 5-6$ Lyman-$\alpha$ Forest Power Spectrum: the Outlook after Planck · Introduction · 0.87
The UV background models are an important input to hydrodynamical simulations of structure formation to efficiently model the ionization and thermal state of the IGM [ref] .

Simulating the epoch of Helium Reionization in photon-conserving semi-numerical code SCRIPT · Introduction · 0.92
Astrophysical applications include measuring the thermal history of the Universe [ref] , ionizing background models [ref] , the timing of reionization [ref] , and creating 3D maps of neutral hydrogen density [ref] .

PRIYA: A New Suite of Lyman-alpha Forest Simulations for Cosmology · Introduction · 0.88

What it cites · 12 sentences without a confident label

Contests 1 paper

Finally, we want to point out that both the [ref] and [ref] final conclusions on possible $$ reionization scenarios are based only on [ref] measurements at high redshift ($z>4$), ignoring the constraints on $T_0$ given by [ref] , which point to a much hotter IGM.

Models of the Thermal Evolution of the Intergalactic Medium After Reionization · Comparison to Previous Work · contest 0.78

Uses data or values from 2 papers

The observational constraints on $$ coming from the CMB [ref] are indicated by a gray band[During the making of this paper, new constraints on reionization from Planck were published [ref] , moving these constraints to a lower value and reducing the errors: $=0.058±0.012$.

Planck intermediate results. XLVI. Reduction of large-scale systematic effects in HFI polarization maps and estimation of the reionization optical depth · Ionization and Thermal Histories of Common UVB Models · 0.90
The observational constraints on $$ coming from the CMB [ref] are indicated by a gray band[During the making of this paper, new constraints on reionization from Planck were published [ref] , moving these constraints to a lower value and reducing the errors: $=0.058±0.012$.

Planck 2015 results. XIII. Cosmological parameters · Ionization and Thermal Histories of Common UVB Models · 0.90

Cites as background 5 papers

Despite significant progress on this front [ref] these simulations are still too costly for sensible exploration of the parameter space.

Cosmic Dawn (CoDa): the First Radiation-Hydrodynamics Simulation of Reionization and Galaxy Formation in the Local Universe · Introduction · 0.90
These include simulations focusing on the properties of the IGM [ref] , but also simulations modeling galaxy formation and evolution [ref] .

MUFASA: Galaxy Formation Simulations With Meshless Hydrodynamics · Ionization and Thermal Histories of Common UVB Models · 0.88
These models could include Population III stars [ref] , X-ray pre-heating coming from from starburst galaxies, supernova remnants, or miniquasars [ref] , dark matter annihilation or decay [ref] or cosmic rays [ref] , from the intergalactic absorption of blazar TeV photons [ref] , or from broadband intergalactic dust absorption [ref] .

Intergalactic dust and its photoelectric heating · Conclusions · 0.89

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