The photoheating of the intergalactic medium in synthesis models of the UV background

Puchwein, Ewald; Bolton, James S.; Haehnelt, Martin G.; Madau, Piero; Becker, George D.; Haardt, Francesco

doi:10.1093/mnras/stv773

Cited by 117 publications

(202 citation statements)

References 87 publications

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“…The solution to this equation yields the correct slope of γ − 1 = 1/(1 + β). The Puchwein et al (2014) approach does hold insight into what sets the asymptotic slope, and indeed is our solution specializing to the case in which the density of a gas parcel is constant in time (our solutions for n = 3). However, this explanation ignores the adiabatic cooling associated with the dilation of space, the primary reason why memory of the initial conditions is lost within a doubling time of the scale factor.…”

Section: Previous Explanations For γmentioning

confidence: 98%

“…Subsequently, ⋆ mcquinn@uw.edu 1 Most studies that use numerical simulations implicitly adopt such a parametrization, as standard cosmological simulations employ uniform radiation backgrounds -an approximation which guarantees a near power-law relation. Theuns et al (1998) and Puchwein et al (2014) attempted to provide more intuitive derivations that we show are problematic. In addition, previous studies did not address how non-adiabatic cooling processes affect this relation, namely Compton cooling off of the cosmic microwave background (CMB) and recombination cooling.…”

Section: Introductionmentioning

confidence: 99%

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On the intergalactic temperature–density relation

McQuinn

Sanderbeck

2015

Mon. Not. R. Astron. Soc.

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Cosmological simulations of the low-density intergalactic medium exhibit a strikingly tight power-law relation between temperature and density that holds over two decades in density. It is found that this relation should roughly apply ∆z ∼ 1 − 2 after a reionization event, and this limiting behavior has motivated the power-law parameterizations used in most analyses of the Lyα forest. This relation has been explained by using equations linearized in the baryonic overdensity (which does not address why a tight power-law relation holds over two decades in density) or by equating the photoheating rate with the cooling rate from cosmological expansion (which we show is incorrect). Previous explanations also did not address why recombination cooling and Compton cooling off of the cosmic microwave background, which are never negligible, do not alter the character of this relation. We provide an understanding for why a tight power-law relation arises for unshocked gas at all densities for which collisional cooling is unimportant. We also use our results to comment on (1) how quickly fluctuations in temperature redshift away after reionization processes, (2) how much shock heating occurs in the low-density intergalactic medium, and (3) how the temperatures of collapsing gas parcels evolve.

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Section: Previous Explanations For γmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

On the intergalactic temperature–density relation

McQuinn

Sanderbeck

2015

Mon. Not. R. Astron. Soc.

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“…A small modification to the He II photoheating rate, HeII = 1.7 HM12 HeII for 2.2 < z < 3.4, is applied to match observational measurements of the IGM temperature at mean density, T 0 , inferred from the curvature of Ly α forest absorption lines (Becker et al 2011). A boost to the IGM temperature from non-equilibrium and radiative transfer effects during He II reionization is expected at these redshifts (Abel & Haehnelt 1999;McQuinn et al 2009;Puchwein et al 2015).…”

Section: Hydrodynamical Simulationsmentioning

confidence: 99%

The Sherwood simulation suite: overview and data comparisons with the Lyman α forest at redshifts 2 ≤z≤ 5

Bolton

Puchwein²,

Sijacki³

et al. 2016

Mon. Not. R. Astron. Soc.

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182

218

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We introduce a new set of large scale, high resolution hydrodynamical simulations of the intergalactic medium: the Sherwood simulation suite. These are performed in volumes 10 3 -160 3 h −3 comoving Mpc 3 , span almost four orders of magnitude in mass resolution with up to 17.2 billion particles, and employ a variety of physics variations including warm dark matter and galactic outflows. We undertake a detailed comparison of the simulations to high resolution, high signal-to-noise observations of the Lyα forest over the redshift range 2 ≤ z ≤ 5. The simulations are in very good agreement with the observational data, lending further support to the paradigm that the Lyα forest is a natural consequence of the web-like distribution of matter arising in ΛCDM cosmological models. Only a small number of minor discrepancies remain with respect to the observational data. Saturated Lyα absorption lines with column densities N HI > 10 14.5 cm −2 at 2 < z < 2.5 are underpredicted in the models. An uncertain correction for continuum placement bias is required to match the distribution and power spectrum of the transmitted flux, particularly at z > 4. Finally, the temperature of intergalactic gas in the simulations may be slightly too low at z = 2.7 and a flatter temperature-density relation is required at z = 2.4, consistent with the expected effects of non-equilibrium ionisation during He II reionisation.

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“…The photoionization and photoheating rates are given by those in HM12. This allows for a comparison with other studies that employ a uniform UV background (Becker et al 2011a;Puchwein et al 2015). However, for a fair comparison with the other simulations presented here, we have renormalized these rates to match τ eff as outlined in Section 2.3.…”

Section: Details Of the Simulation Suitementioning

confidence: 99%

“…The interplay of these two factors determines the temperature of these regions of average density. The average temperature of these regions show two characteristic bumps as a function of redshift: one initial increase from T ∼ 200 K to T ∼ 10 4 K as a result of hydrogen reionization at 8 z 10, and a subsequent increase in temperature from T ∼ 10 4 K to T ∼ 2 × 10 4 K at 2 z 3.5 as a result of helium reionization (Furlanetto & Oh 2008;Puchwein et al 2015;Upton Sanderbeck et al 2016). In between the two epochs of reionization, and following helium ii reionization, adiabatic cooling dominates, and so the average temperature decreases.…”

Section: Temperature At Mean Densitymentioning

confidence: 99%

Helium Reionization Simulations. II. Signatures of Quasar Activity on the IGM

Plante

Trac

Croft

et al. 2017

ApJ

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We have run a new suite of simulations that solve hydrodynamics and radiative transfer simultaneously to study helium ii reionization. Our suite of simulations employs various models for populating quasars inside of dark matter halos, which affect the He ii reionization history. In particular, we are able to explore the impact that differences in the timing and duration of reionization have on observables. We examine the thermal signature that reionization leaves on the IGM, and measure the temperaturedensity relation. As previous studies have shown, we confirm that the photoheating feedback from helium ii reionization raises the temperature of the intergalactic medium (IGM) by several thousand kelvin. To compare against observations, we generate synthetic Lyα forest sightlines on-the-fly and match the observed effective optical depth τ eff (z) of hydrogen to recent observations. We show that when the simulations have been normalized to have the same values of τ eff , the effect that helium ii reionization has on observations of the hydrogen Lyα forest is minimal. Specifically, the flux PDF and the one-dimensional power spectrum are sensitive to the thermal state of the IGM, but do not show direct evidence for the ionization state of helium. We show that the peak temperature of the IGM typically corresponds to the time of 90-95% helium ionization by volume, and is a relatively robust indicator of the timing of reionization. Future observations of helium reionization from the hydrogen Lyα forest should thus focus on measuring the temperature of the IGM, especially at mean density. Detecting the peak in the IGM temperature would provide valuable information about the timing of the end of helium ii reionization.

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The photoheating of the intergalactic medium in synthesis models of the UV background

Cited by 117 publications

References 87 publications

On the intergalactic temperature–density relation

On the intergalactic temperature–density relation

The Sherwood simulation suite: overview and data comparisons with the Lyman α forest at redshifts 2 ≤z≤ 5

Helium Reionization Simulations. II. Signatures of Quasar Activity on the IGM

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