THE END OF HELIUM REIONIZATION AT
                    <i>z</i>
                    ≃ 2.7 INFERRED FROM COSMIC VARIANCE IN
                    <i>HST</i>
                    /COS He II Lyα ABSORPTION SPECTRA

Worseck, G.; Prochaska, J. Xavier; McQuinn, Matthew; Dall'Aglio, Aldo; Fechner, C.; Reimers, D.; Richter, Philipp; Wisotzki, L.

doi:10.1088/2041-8205/733/2/l24

Cited by 102 publications

(103 citation statements)

References 49 publications

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“…Among the models shown for comparison is a simulation with a uniform UV background from Haardt & Madau (2012) (Simulation H6). Note that most of the simulations reach a 99% ionization fraction in the range of 2.7 z 3, which is consistent with observational findings (Dixon & Furlanetto 2009;Worseck et al 2011). In all simulations, the duration of helium ii reionization is typically 0.8 ∆ 50 1, with the notable exceptions of Simulations H4 and H6.…”

Section: Details Of the Simulation Suitesupporting

confidence: 87%

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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Section: Details Of the Simulation Suitesupporting

confidence: 87%

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

Plante

Trac

Croft

et al. 2017

ApJ

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“…where f e accounts for redshift evolution of helium contribution, we use f e = (0.76 + 0.24/0.76/4) for z > 2.8 and f e = (0.76 + 0.24/0.76/2) for z ≤ 2.8, approximating He II reionization as a step function at z = 2.8, which is consistent with the observed He II absorption optical depth data of (Worseck et al 2011), interpreted in the context of He II reionization simulations of (McQuinn et al 2009). And f s and f n account for stellar density and neutral hydrogen density, respectively, which do not contribute to electron density.…”

Section: Reionization Histories Constrained By the State Of Igm At Z supporting

confidence: 64%

Constraint on Matter Power Spectrum on 10⁶–10⁹ M_⊙ Scales from τ_e

Cen

2017

ApJ

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An analysis of the physics-rich endgame of reionization at z = 5.7 is performed, utilizing jointly the observations of the Lyα forest, the mean free path of ionizing photons, the luminosity function of galaxies and new physical insight. We find that an upper limit on τ e provides a constraint on the minimum mean free path (of ionizing photons) that is primarily due to dwarf galaxies, which in turn yields a new and yet the strongest constraint on the matter power spectrum on 10 6 − 10 9 M scales. With the latest Planck measurements of τ e = 0.055 ± 0.009, we can place an upper limit of (8.9 × 10 6 , 3.8 × 10 7 , 4.2 × 10 8 ) M on the lower cutoff mass of the halo mass function, or equivalent a lower limit on warm dark matter particle mass m x ≥ (15.1, 9.8, 4.6)keV or on sterile neutrino mass m s ≥ (161, 90, 33)keV, at (1, 1.4, 2.2)σ confidence level, respectively.

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“…These high-energy photons are produced predominantly in active galactic nuclei (AGNs), but are also strongly attenuated by intergalactic He ii at z > 4, since He ii reionization likely does not occur until z 3.5, and perhaps even lower redshift (Shull et al 2010;Worseck et al 2011). C iv systems-particularly the strong ones which dominate Ω C iv -may be preferentially present in He ii-ionized bubbles surrounding sites of galaxy formation and/or AGN activity, where the radiation field and abundances are both enhanced.…”

Section: Discussionmentioning

confidence: 99%

CONSTRAINTS ON THE UNIVERSAL C IV MASS DENSITY ATz∼ 6 FROM EARLY INFRARED SPECTRA OBTAINED WITH THE MAGELLAN FIRE SPECTROGRAPH

Simcoe

Cooksey

Matejek

et al. 2011

ApJ

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We present a new determination of the intergalactic C iv mass density at 4.3 < z < 6.3. Our constraints are derived from high signal-to-noise spectra of seven quasars at z > 5.8 obtained with the newly commissioned Folded-Port Infrared Echellette (FIRE) spectrograph on the Magellan Baade telescope, coupled with six observations of northern objects taken from the literature. We confirm the presence of a downturn in the C iv abundance at z = 5.66 by a factor of 4.1 relative to its value at z = 4.96, as measured in the same sight lines. In the FIRE sample, a strong system previously reported in the literature as C iv at z = 5.82 is re-identified as Mg ii at z = 2.78, leading to a substantial downward revision in Ω C iv for these prior studies. Additionally, we confirm the presence of at least two systems with low-ionization C ii, Si ii, and O i absorption but relatively weak signal from C iv. The latter systems may be of interest if the downward trend in Ω C iv at high redshift is driven in part by ionization effects.

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THE END OF HELIUM REIONIZATION AT z ≃ 2.7 INFERRED FROM COSMIC VARIANCE IN HST /COS He II Lyα ABSORPTION SPECTRA

Cited by 102 publications

References 49 publications

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

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

Constraint on Matter Power Spectrum on 10⁶–10⁹ M_⊙ Scales from τ_e

CONSTRAINTS ON THE UNIVERSAL C IV MASS DENSITY ATz∼ 6 FROM EARLY INFRARED SPECTRA OBTAINED WITH THE MAGELLAN FIRE SPECTROGRAPH

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THE END OF HELIUM REIONIZATION AT z ≃ 2.7 INFERRED FROM COSMIC VARIANCE IN HST /COS He II Lyα ABSORPTION SPECTRA

Cited by 102 publications

References 49 publications

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

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

Constraint on Matter Power Spectrum on 106–109 M⊙ Scales from τe

CONSTRAINTS ON THE UNIVERSAL C IV MASS DENSITY ATz∼ 6 FROM EARLY INFRARED SPECTRA OBTAINED WITH THE MAGELLAN FIRE SPECTROGRAPH

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Constraint on Matter Power Spectrum on 10⁶–10⁹ M_⊙ Scales from τ_e