The intergalactic medium thermal history at redshift<i>z</i>= 1.7-3.2 from the Lyα forest: a comparison of measurements using wavelets and the flux distribution

Garzilli, Antonella; Bolton, James S.; Kim, T.-S.; Leach, S.; Viel, Matteo

doi:10.1111/j.1365-2966.2012.21223.x

Cited by 81 publications

(101 citation statements)

References 63 publications

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“…The good agreement of our measurements of T0 and the evolution of T0 inferred from the extrapolation of the temperature measurements with the curvature method to mean density based on the γ values predicted by the Puchwein et al (2015) simulation is a non-trivial result that suggests that our understanding of the thermal state IGM is converging from multiple different approaches. Convergence of results is also suggested by the measurements of T0 obtained with a wavelet-analysis technique by Lidz et al (2010) (cyan triangles) and Garzilli et al (2012) (grey pentagons). The discrepancy with their measurements in the redshift bins close to that of our measurement is less than 1σ.…”

Section: Discussionmentioning

confidence: 60%

A new measurement of the intergalactic temperature at z ∼ 2.55–2.95

Rorai

Carswell

Haehnelt

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present two measurements of the temperature-density relationship (TDR) of the intergalactic medium (IGM) in the redshift range 2.55 < z < 2.95 using a sample of 13 high-quality quasar spectra and high resolution numerical simulations of the IGM. Our approach is based on fitting the neutral hydrogen column density N HI and the Doppler parameter b of the absorption lines in the Lyα forest. The first measurement is obtained using a novel Bayesian scheme which takes into account the statistical correlations between the parameters characterising the lower cut-off of the b − N HI distribution and the power-law parameters T 0 and γ describing the TDR. This approach yields T 0 /10 3 K = 15.6 ± 4.4 and γ = 1.45 ± 0.17 independent of the assumed pressure smoothing of the small scale density field. In order to explore the information contained in the overall b − N HI distribution rather than only the lower cut-off, we obtain a second measurement based on a similar Bayesian analysis of the median Doppler parameter for separate column-density ranges of the absorbers. In this case we obtain T 0 /10 3 K = 14.6 ± 3.7 and γ = 1.37 ± 0.17 in good agreement with the first measurement. Our Bayesian analysis reveals strong anti-correlations between the inferred T 0 and γ for both methods as well as an anti-correlation of the inferred T 0 and the pressure smoothing length for the second method, suggesting that the measurement accuracy can in the latter case be substantially increased if independent constraints on the smoothing are obtained. Our results are in good agreement with other recent measurements of the thermal state of the IGM probing similar (over-)density ranges.

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Section: Discussionmentioning

confidence: 60%

A new measurement of the intergalactic temperature at z ∼ 2.55–2.95

Rorai

Carswell

Haehnelt

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…Information on the thermal state of the IGM has been extracted from the H I Lyα forest by decomposing it into individual absorption lines (Schaye et al 2000;Ricotti et al 2000;Bryan & Machacek 2000;McDonald et al 2001;Rudie et al 2012;Bolton et al 2014;Rorai et al 2018;Hiss et al 2018) or by treating it as a continuous field using various transmission statistics, i.e. the probability distribution function (Bolton et al 2008;Viel et al 2009;Calura et al 2012;Lee et al 2015;Rorai et al 2017a), the power spectrum (Zaldarriaga et al 2001;Walther et al 2018Walther et al , 2019, the transmission curvature (Becker et al 2011;Boera et al 2014), wavelet decomposition Lidz et al 2010;Garzilli et al 2012), and the quasar pair phase angle distribution (Rorai et al 2017b). Despite large statistical errors and some remaining tension between the measurements, these studies indicate an extended heating of the IGM from z 6 (Bolton et al 2010;Bolton et al 2012) to z 2.8 (Schaye et al 2000;Becker et al 2011;Boera et al 2014;Hiss et al 2018) expected from an extended He II reionization process.…”

Section: Introductionmentioning

confidence: 99%

The Evolution of the He ii-ionizing Background at Redshifts 2.3 < z < 3.8 Inferred from a Statistical Sample of 24 HST/COS He ii Lyα Absorption Spectra*

Worseck

Davies

Prochaska

2019

ApJ

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We present measurements of the large-scale (≈ 40 comoving Mpc) effective optical depth of He II Lyα absorption, τ eff , at 2.54 < z < 3.86 toward 16 He II-transparent quasars observed with the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST), to characterize the ionization state of helium in the intergalactic medium (IGM). We provide the first statistical sample of τ eff measurements in six signal-to-noise ratio 3 He II sightlines at z > 3.5, and study the redshift evolution and sightline-to-sightline variance of τ eff in 24 He II sightlines. We confirm an increase of the median τ eff from 2 at z = 2.7 to τ eff 5 at z > 3, and a scatter in τ eff that increases with redshift. The z > 3.5 He II absorption is predominantly saturated, but isolated narrow (∆v < 650 km s −1 ) transmission spikes indicate patches of reionized helium. We compare our measurements to predictions for a range of UV background models applied to outputs of a large-volume (146 comoving Mpc) 3 hydrodynamical simulation by forward-modeling our sample's quality and size. At z > 2.74 the variance in τ eff significantly exceeds expectations for a spatially uniform UV background, but is consistent with a fluctuating radiation field sourced by variations in the quasar number density and the mean free path in the post-reionization IGM. We develop a method to infer the approximate median He II photoionization rate Γ HeII of a fluctuating UV background from the median τ eff , finding a factor 5 decrease in Γ HeII between z 2.6 and z 3.1. At z 3.1 a Γ HeII = 9.1 +1.1 −1.2 (stat.) +2.4 −3.4 (sys.) × 10 −16 s −1 corresponds to a median He II fraction of 2.5%, indicating that our data probe the tail end of He II reionization.

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“…There is a wide range of evidence from Lyman-α forest data to support heating from He II reionization at z < 6 Ricotti et al 2000;Bryan & Machacek 2000;Zaldarriaga et al 2001;McDonald et al 2001;Lidz et al 2010;Becker et al 2011;Garzilli et al 2012;Bolton et al 2012), but see Puchwein et al (2012) for possible additional contributions to the observed heating.…”

Section: Introductionmentioning

confidence: 99%

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

Puchwein

Bolton

Haehnelt

et al. 2015

Monthly Notices of the Royal Astronomical Society

117

174

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We compare cosmological hydrodynamical simulations combined with the homogeneous metagalactic UV background (UVB) of Haardt & Madau (2012) (HM2012) to observations of the Lyman-α forest that are sensitive to the thermal and ionization state of the intergalactic medium (IGM). The transition from optically thick to thin photoheating predicted by the simple one-zone, radiative transfer model implemented by HM2012 predicts a thermal history that is in remarkably good agreement with the observed rise of the IGM temperature at z ∼ 3 if we account for the expected evolution of the volume filling factor of He III. Our simulations indicate that there may be, however, some tension between the observed peak in the temperature evolution and the rather slow evolution of the He II opacities suggested by recent Hubble Space Telescope/COS measurements. The HM2012 UVB also underpredicts the metagalactic hydrogen photoionization rate required by our simulations to match the observed opacity of the forest at z > 4 and z < 2.

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The intergalactic medium thermal history at redshiftz= 1.7-3.2 from the Lyα forest: a comparison of measurements using wavelets and the flux distribution

Cited by 81 publications

References 63 publications

A new measurement of the intergalactic temperature at z ∼ 2.55–2.95

A new measurement of the intergalactic temperature at z ∼ 2.55–2.95

The Evolution of the He ii-ionizing Background at Redshifts 2.3 < z < 3.8 Inferred from a Statistical Sample of 24 HST/COS He ii Lyα Absorption Spectra*

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

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