The Thermal Memory of Reionization History

By L. Hui, Zoltán Haiman. 2003

191 citations recorded by the source corpus.

The recent measurement by WMAP of a large electron-scattering optical depth τe = 0.17 ± 0.04 is consistent with a simple model of reionization in which the intergalactic medium (IGM) is ionized at redshift z ~ 15 and remains highly ionized thereafter. Here we show that existing measurements of the IGM temperature from the Lyα forest at z ~ 2-4 rule out this "vanilla" model. Under reasonable assumptions about the ionizing spectrum, as long as the universe is reionized before z = 10 and remains highly ionized thereafter, the IGM reaches an asymptotic thermal state that is too cold compared to observations. To simultaneously satisfy the cosmic microwave background and Lyα forest constraints, the reionization history must be complex: reionization begins early at z ≳ 15, but there must have been significant (order-of-unity) changes in fractions of neutral hydrogen and/or helium at 6 < z < 10 and/or singly ionized helium at 4 < z < 10. We describe a physically motivated reionization model that satisfies all current observations. We also explore the impact of a stochastic reionization history and show that a late epoch of (He → He ) reionization induces a significant scatter in the IGM temperature, but the scatter diminishes with time quickly. Finally, we provide an analytic formula for the thermal asymptote and discuss possible additional heating mechanisms that might evade our constraints.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/0066b105966e2d0c127538d4fea1d2d511026660

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Citations in the corpus

21 Centimeter Fluctuations from Cosmic Gas at High Redshifts (2003, background): “10 (Theuns et al. 2002; Hui & Haiman 2003), although this argument depends on the timing and history of He II reionization (e.g., Sokasian et al. 2002).”
Ultralight scalars as cosmological dark matter (2016, background): “Because different patches of the medium reionize at different times due to fluctuations in the distribution of ionizing sources and absorbing materials, the temperature could vary by a factor of a few at redshift ∼ 5 if the reionization of different patches spans the redshift range ∼ 7–10 [178, 179]”
The Evolution of Optical Depth in the Lyα Forest: Evidence Against Reionization at z~6 (2006, unknown): “Additional arguments may be made about the thermal history of the IGM (Theuns et al. 2002; Hui & Haiman 2003) or the apparent size of the transmission regions around z ∼ 6 QSOs (Mesinger & Haiman 2004; Mesinger et al. 2004; Wyithe & Loeb 2004; Fan et al. 2006).”
Galaxy UV-luminosity function and reionization constraints on axion dark matter (2014, background): “The assumed IGM temperature is appropriate for ionised gas at the mean density during the epoch of reionisation (Hui & Haiman 2003).”
NEW CONSTRAINTS ON COSMIC REIONIZATION FROM THE 2012 HUBBLE ULTRA DEEP FIELD CAMPAIGN (2013, unknown): “Transforming those into constraints on the ionized fraction requires a model that: (1) predicts the temperature evolution of the IGM (Hui & Haiman 2003; Trac et al. 2008; Furlanetto & Oh 2009); (2) describes the distribution of gas densities in the IGM (Miralda-Escudé et al. 2000; Bolton & Becker…”
21-cm fluctuations from inhomogeneous X-ray heating before reionization (2006, background): “At low redshift, observations of the Lyα forest place constraints on the temperature of the IGM after reionization (Schaye et al. 2000; McDonald et al. 2001; Zaldarriaga, Hui & Tegmark 2001; Theuns et al. 2002; Hui & Haiman 2003).”
New Limits on 21cm EoR From PAPER-32 Consistent with an X-Ray Heated IGM at z=7.7 (2013, background): “Note that our measurements pertain to the thermal evolution of the neutral gas during reionization, and not the subsequent thermal evolution of the ionized gas after reionization (Hui & Haiman 2003).”
Statistical Probes of Reionization with 21 Centimeter Tomography (2004, background): “10 (Theuns et al. 2002; Hui & Haiman 2003), although this argument depends on the characteristics of HeII reionization (e.g., Sokasian et al. 2002).”
FORMATION RATES OF POPULATION III STARS AND CHEMICAL ENRICHMENT OF HALOS DURING THE REIONIZATION ERA (2009, methodology): “Several models had been proposed (Venkatesan et al. 2003; Cen 2003; Wyithe & Loeb 2003; Hui & Haiman 2003; Stiavelli et al. 2004) and many of these included a significant contribution from first stars to τe.”
The First Cosmic Structures and Their Effects (2004, background): “A simple scenario in which the IGM reionized early (zion > 10, as suggested by the last condition) and remains so thereafter, is ruled out as the IGM would reach an asymptotic thermal state too cold compared to observations (Theuns, Schaye & Haehnelt 2000; Hui & Haiman 2003; Wyithe & Loeb 2003b).”
Constraining the Evolution of the Ionizing Background and the Epoch of Reionization with z ∼ 6 Quasars. II. A Sample of 19 Quasars (2005, background): “• The observed temperature evolution of the IGM at z ∼ 3− 5 suggests that the reionization epoch is not much higher than 8 (Hui & Haiman 2003).”
Reionization and the Cosmic Dawn with the Square Kilometre Array (2012, background): “The size and distribution of ionized regions will give us information about how patchy and extended the reionization process was, relevant for understanding the temperature structure of the IGM for a substantial period after reionization (Theuns et al. 2002; Hui & Haiman 2003).”
Early Reionization by Miniquasars (2003, background): “He II reionization by miniquasars at z ∼> 10 would provide a significant boost to the gas temperature, with interesting implications for the thermal history of the IGM (e.g. Hui & Haiman 2003).”
LOWER-LUMINOSITY GALAXIES COULD REIONIZE THE UNIVERSE: VERY STEEP FAINT-END SLOPES TO THE UV LUMINOSITY FUNCTIONS AT z ⩾ 5–8 FROM THE HUDF09 WFC3/IR OBSERVATIONS (2011, methodology): “This is to account for the substantial heating of the IGM due to the reionization process itself (Hui & Haiman 2003).”
The observed ionization rate of the intergalactic medium and the ionizing emissivity at z≥ 5: evidence for a photon-starved and extended epoch of reionization (2007, background): “Therefore, T0 may reach 1.5–2 × 104 K if hydrogen and single helium reionization occurred just above z = 6 (Hui & Haiman 2003), although if hydrogen reionization occurred earlier T0 may be as low as 0.5 × 104 K.”
The First Stars (2003, background): “The first one considers the thermal history of the postreionization IGM (e.g., Theuns et al. 2002, Hui & Haiman 2003).”