Models of the thermal evolution of the intergalactic medium after reionization

Sanderbeck, Phoebe R. Upton; D’Aloisio, Anson; McQuinn, Matthew

doi:10.1093/mnras/stw1117

Cited by 97 publications

(122 citation statements)

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“…However, there is generally a lack of consistency between these measurements and those from other studies (Ricotti et al 2000;McDonald et al 2001;Zaldarriaga et al 2001;Lidz et al 2010). In particular Lidz et al (2010) found evidence for a much hotter IGM at z 3.5 than expected from current models (Puchwein et al 2015;Upton Sanderbeck et al 2016;Oñorbe et al 2016), in disagreement with Becker et al (2011).…”

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confidence: 75%

“…Irrespective of the nature of these sources, if they reionized intergalactic helium at z 4, these sources also likely contributed substantially to H I reionization (Madau & Haardt 2015). Unfortunately, it is not currently possible to probe the ionization state of He II via far-UV He II Lyα absorption at z 4, and constraints on He II reionization from the thermal state of the IGM do not all agree (Lidz et al 2010;Becker et al 2011;Upton Sanderbeck et al 2016). This paper introduces a new method to constrain the timing of He II reionization.…”

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confidence: 99%

“…Hydrodynamical simulations show that within several hundred Myr of reionization, IGM gas relaxes onto a tight power law temperature-density relation T = T 0 (ρ/ρ) γ−1 , where T 0 is the temperature at the cosmic mean density, ρ (Hui & Gnedin 1997;. However, quasar driven He II reionization, which is thought to increase the temperature of the IGM by ∆T ≃ 5 − 10 × 10 3 K at z ≃ 3 − 4 (McQuinn et al 2009;Compostella et al 2013), can lead to a significant changes in this relation (McQuinn et al 2009;Upton Sanderbeck et al 2016;La Plante et al 2016). A comparable temperature increase at z ≃ 3 was reported by Schaye et al (2000) (see also Theuns et al 2002c), which was later qualitatively supported by Becker et al (2011).…”

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confidence: 99%

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The Thermal Proximity Effect: A New Probe of the He ii Reionization History and Quasar Lifetime

Khrykin

Hennawi

McQuinn

2017

ApJ

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Despite decades of effort, the timing and duration of He II reionization and the properties of the quasars believed to drive it, are still not well constrained. We present a new method to study both via the thermal proximity effect -the heating of the intergalactic medium (IGM) around quasars when their radiation doubly ionizes helium. We post-process hydrodynamical simulations with 1D radiative transfer and study how the thermal proximity effect depends on He II fraction, x HeII,0 , which prevailed in the IGM before the quasar turned on, and the quasar lifetime t Q . We find that the amplitude of the temperature boost in the quasar environment depends on x HeII,0 , with a characteristic value of ∆T ≃ 10 4 K for x HeII,0 = 1.0, whereas the size of the thermal proximity zone is sensitive to t Q ,with typical sizes of ≃ 100 cMpc for t Q = 10 8 yr. This temperature boost increases the thermal broadening of H I absorption lines near the quasar. We introduce a new Bayesian statistical method based on measuring the Lyα forest power spectrum as a function of distance from the quasar, and demonstrate that the thermal proximity effect should be easily detectable. For a mock dataset of 50 quasars at z ≃ 4, we predict that one can measure x HeII,0 to an (absolute) precision ≈ 0.04, and t Q to a precision of ≈ 0.1 dex. By applying our formalism to existing high-resolution Lyα forest spectra, one should be able to reconstruct the He II reionization history,providing a global census of hard photons in the high-z universe.

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confidence: 75%

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confidence: 99%

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confidence: 99%

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The Thermal Proximity Effect: A New Probe of the He ii Reionization History and Quasar Lifetime

Khrykin

Hennawi

McQuinn

2017

ApJ

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“…Equally poorly understood is the thermal history of the IGM, which reflects the timing and duration of reionization as well as the nature of ionizing sources. Measurements of the IGM temperature evolution from redshift 2 to 5 are not consistent with the monotonic increase with redshift expected after the completion of hydrogen reionization, and require a substantial injection of additional energy, likely from the photoionization of He II (Becker et al 2011;Upton Sanderbeck et al 2015). …”

Section: Introductionmentioning

confidence: 87%

Radiation Backgrounds at Cosmic Dawn: X-Rays from Compact Binaries

Madau

Fragos

2017

ApJ

341

391

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We compute the expected X-ray diffuse background and radiative feedback on the intergalactic medium (IGM) from X-ray binaries prior and during the epoch of reionization. The cosmic evolution of compact binaries is followed using a population synthesis technique that treats separately neutron stars and black hole binaries in different spectral states and is calibrated to reproduce the observed X-ray properties of galaxies at z ∼ < 4. Together with an updated empirical determination of the cosmic history of star formation, recent modeling of the stellar mass-metallicity relation, and a scheme for absorption by the IGM that accounts for the presence of ionized H II bubbles during the epoch of reionization, our detailed calculations provide refined predictions of the X-ray volume emissivity and filtered radiation background from "normal" galaxies at z ∼ > 6. Radiative transfer effects modulate the background spectrum, which shows a characteristic peak between 1 and 2 keV. Because of the energy dependence of photoabsorption, soft X-ray photons are produced by local sources, while more energetic radiation arrives unattenuated from larger cosmological volumes. While the filtering of Xray radiation through the IGM slightly increases the mean excess energy per photoionization, it also weakens the radiation intensity below 1 keV, lowering the mean photoionization and heating rates. Numerical integration of the rate and energy equations shows that the contribution of X-ray binaries to the ionization of the bulk IGM is negligible, with the electron fraction never exceeding 1%. Direct He I photoionizations are the main source of IGM heating, and the temperature of the largely neutral medium in between H II cavities increases above the temperature of the cosmic microwave background (CMB) only at z ∼ < 10, when the volume filling factor of H II bubbles is already ∼ > 0.1. Therefore, in this scenario, it is only at relatively late epochs that neutral intergalactic hydrogen may be observable in 21-cm emission against the CMB.

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“…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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Models of the thermal evolution of the intergalactic medium after reionization

Cited by 97 publications

References 75 publications

The Thermal Proximity Effect: A New Probe of the He ii Reionization History and Quasar Lifetime

The Thermal Proximity Effect: A New Probe of the He ii Reionization History and Quasar Lifetime

Radiation Backgrounds at Cosmic Dawn: X-Rays from Compact Binaries

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

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