Detection of extended He II reionization in the temperature evolution of the intergalactic medium

By George D. Becker, J. Bolton, M. Haehnelt, Wallace L. W. Sargent KICCIoA Cambridge, Melbourne., Caltech. 2010

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We present new measurements of the temperature of the intergalactic medium (IGM) derived from the Lyα forest over 2.0 ≤ z ≤ 4.8. The small-scale structure in the forest of 61 high-resolution quasi-stellar object spectra is quantified using a new statistic, the curvature, and the conversion to temperature calibrated using a suite of hydrodynamic simulations. At each redshift, we focus on obtaining the temperature at an optimal overdensity probed by the Lyα forest, T(Δ[overbar]), where the temperature is nearly a one-to-one function of the curvature regardless of the slope of the temperature–density relation. The median 2σ statistical uncertainty in these measurements is 8 per cent, though there may be comparable systematic errors due to the unknown amount of Jeans smoothing in the IGM. We use our T(Δ[overbar]) results to infer the temperature at the mean density, T_0. Even for a maximally steep temperature–density relation, T_0 must increase from ~8000 K at z ≃ 4.4 to ≳ 12 000 K at z ≃ 2.8. This increase is not consistent with the monotonic decline in T0 expected in the absence of He ii reionization. We therefore interpret the observed rise in temperature as evidence of He ii reionization beginning at z ≳ 4.4. The evolution of T_0 is consistent with an end to He ii reionization at z ~ 3, as suggested by opacity measurements of the He ii Lyα forest, although the redshift at which T_0 peaks will depend somewhat on the evolution of the temperature–density relation. These new temperature measurements suggest that the heat input due to the reionization of He ii dominates the thermal balance of the IGM over an extended period with Δz ≳ 1.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/a810022fed7fc4b4acabcdb3e98038cb1a096787

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Citations in the corpus

New Constraints on the free-streaming of warm dark matter from intermediate and small scale Lyman-$\alpha$ forest data (2017, methodology): “The mean flux evolution derived from the SDSS-III/BOSS analysis has values that are 5%–8% lower compared to those measured by [34], but note that the range of values considered in our analysis brackets the observed values by [34] as well.”
Evolution of the AGN UV luminosity function from redshift 7.5 (2018, background): “…evolution in detail, and which are consistent with the measured redshift evolution and scatter of the He ii effective optical depth, as well as the measured redshift evolution of the IGM temperaturedensity relation (e.g. Becker et al. 2011; Boera et al. 2014; Rorai et al. 2018; Hiss et al. 2017).”
Constraining the mass of light bosonic dark matter using SDSS Lyman-α forest (2017, result): “…in the redshift-dependent IGM temperaturedensity relation TIGM = T0(z)(1 + δρ/ρ)γ(z)−1 (11) As for the case of cosmological parameters, we adopt here fixed benchmark parameters such that T0(z = 3) = 14000 K and γ(z = 3) = 1.3, which are in agreement with the measurements from Becker et al. (2011).”
The Evolution of the Intergalactic Medium (2015, background): “The points with error bars in Figure 6 show recent estimates of the IGM temperature, from Becker et al. (2011) and Boera et al. (2014).”
Upper Limits on the 21 cm Epoch of Reionization Power Spectrum from One Night with LOFAR (2017, background): “The current range can easily accommodate photo-ionisation rate measurements (Bolton & Haehnelt 2007; Calverley et al. 2011; Becker et al. 2011), InterGalactic Medium (IGM) temperature measurements (Theuns et al. 2002; Bolton et al. 2010; Becker & Bolton 2013), observations of high-redshift Lyman…”
COSMIC REIONIZATION AFTER PLANCK: COULD QUASARS DO IT ALL? (2015, background): “Measurements of the IGM temperature evolution from redshift 5 to 2 derived from the Lyα forest have been known to be inconsistent with the mononotic decrease with redshift expected after the completion of hydrogen reionization (Becker et al. 2011).”
The Giant Gemini GMOS survey of zem > 4.4 quasars – I. Measuring the mean free path across cosmic time (2014, background): “Studies of the IGM across cosmic time have revealed redshift evolution in many properties of the Lyα forest: temperature (e.g. Lidz et al. 2010; Becker et al. 2011), line density (e.g. Kim et al. 2013), and the flux PDF (e.g. Becker et al. 2007; Kim et al. 2007).”
A refined measurement of the mean transmitted flux in the Lyα forest over 2 < z < 5 using composite quasar spectra (2012, background): “…function and power spectrum, among others, which are used to constrain quantities ranging from the temperature of the IGM (e.g., Schaye et al. 2000; Zaldarriaga et al. 2001; Lidz et al. 2010; Becker et al. 2011) to the free-streaming length of dark matter particles (e.g., Viel et al. 2008).”
Neutrino masses and cosmology with Lyman-alpha forest power spectrum (2015, background): “The latter distribution follows notably well the measurements of [21].”
Evidence of patchy hydrogen reionization from an extreme Lyα trough below redshift six (2014, methodology): “Further evidence for a decline in the UVB from z ∼ 5 to 6 is also potentially seen in the changing ionization state of metal-enriched absorbers over this interval (Ryan-Weber et al. 2009; Becker et al. 2009, 2011b; Simcoe et al. 2011; D’Odorico et al. 2013; Keating et al. 2014).”
Lyman-alpha forests cool warm dark matter (2015, unknown): “3, consistent with the measurements of [37].”
Concordance models of reionization: implications for faint galaxies and escape fraction evolution (2012, methodology): “Estimates of the IGM temperature at z > 4 in fact suggest T0 < 10, 000 K at z ∼ 5− 6 (Becker et al. 2011a; Bolton et al. 2012).”