The DM distribution of unlocalized FRBs yields H0 = 73.8 +14.0/-12.3 km/s/Mpc with 18% uncertainty.
Detection of Extended He II Reionization in the Temperature Evolution of the Intergalactic Medium
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abstract
We present new measurements of the temperature of the intergalactic medium (IGM) derived from the Lyman-alpha forest over 2.0 < z < 4.8. The small-scale structure in the forest of 61 high-resolution QSO 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 Lyman-alpha forest, T(Delta), where the temperature is nearly a one-to-one function of the curvature regardless of the slope of the temperature-density relation. The median 2-sigma 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(Delta) results to infer the temperature at the mean density, T0. Even for a maximally steep temperature-density relation, T0 must increase from ~8000 K at z ~ 4.4 to >~12000 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 T0 is consistent with an end to He II reionization at z ~ 3, as suggested by opacity measurements of the He II Lyman-alpha forest, although the redshift at which T0 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 Delta_z >~ 1.
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A new analytical formalism self-consistently predicts both the ionized fraction x_i(z) and photoionization rate Gamma_HI(z), achieving percent-level accuracy in x_i and 20-30% accuracy in Gamma_HI versus radiative transfer simulations at z less than or equal to 6.
Using idealized synthetic data, knowing the true continuum in Lyα forest auto- and cross-correlations reduces uncertainties on the AP parameter and Ω_m by ~10%, with extension to 240 h^{-1}Mpc scales adding up to ~15% further improvement equivalent to a 40% larger survey area.