Long Dark Gaps in the Lyβ Forest at z &lt; 6: Evidence of Ultra-late Reionization from XQR-30 Spectra

Zhu, Yongda; Becker, George D.; Keating, Laura C.; D’Odorico, V.; Davies, R. L.; Christenson, Holly M.; Bañados, Eduardo; Bian, Fuyan; Bischetti, M.; Chen, Huanqing; Davies, Frederick B.; Eilers, Anna-Christina; Fan, Xiaohui; Gaikwad, Prakash; Greig, Bradley; Haehnelt, Martin G.; Kulkarni, Girish; Lai, Samuel; Pallottini, Andrea; Qin, Yuxiang; Ryan-Weber, E. V.; Walter, Fabian; Wang, Feige; Yang, Jinyi

doi:10.3847/1538-4357/ac6e60

Cited by 47 publications

(31 citation statements)

References 63 publications

(93 reference statements)

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“…In Figure 6, we show the upper limits on x H I from long dark gap size distributions in Lyα and Lyβ forests (Zhu et al 2022), assuming a late reionization that ends at z  5.3 (Nasir & D'Aloisio 2020). Our constraints at z < 6 (Lower panels) Upper limits on the volume-averaged IGM neutral fraction x H I derived from the dark pixel fractions in the Lyα (red) and Lyβ (blue) forests as a function of redshift.…”

Section: Resultsmentioning

confidence: 99%

“…are highly consistent with these upper limits derived from dark gap statistics. We also present constraints on x H I measured from the Lyα effective optical depth (Fan et al 2006;Yang et al 2020a;Bosman et al 2021) (Zhu et al 2022). At z > 7, individual measurements on the neutral hydrogen fraction from quasar damping wings are denoted by hexagons (Greig et al 2017(Greig et al , 2019Bañados et al 2018;Davies et al 2018;Wang et al 2020;Yang et al 2020b et al 2020a).…”

Section: Resultsmentioning

confidence: 99%

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(Nearly) Model-independent Constraints on the Neutral Hydrogen Fraction in the Intergalactic Medium at z ∼ 5–7 Using Dark Pixel Fractions in Lyα and Lyβ Forests

Jin

Yang

Fan

et al. 2023

ApJ

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Cosmic reionization was the last major phase transition of hydrogen from neutral to highly ionized in the intergalactic medium (IGM). Current observations show that the IGM is significantly neutral at z > 7 and largely ionized by z ∼ 5.5. However, most methods to measure the IGM neutral fraction are highly model dependent and are limited to when the volume-averaged neutral fraction of the IGM is either relatively low ( x ¯ H I ≲ 10 − 3 ) or close to unity ( x ¯ H I ∼ 1 ). In particular, the neutral fraction evolution of the IGM at the critical redshift range of z = 6–7 is poorly constrained. We present new constraints on x ¯ H I at z ∼ 5.1–6.8 by analyzing deep optical spectra of 53 quasars at 5.73 < z < 7.09. We derive model-independent upper limits on the neutral hydrogen fraction based on the fraction of “dark” pixels identified in the Lyα and Lyβ forests, without any assumptions on the IGM model or the intrinsic shape of the quasar continuum. They are the first model-independent constraints on the IGM neutral hydrogen fraction at z ∼ 6.2–6.8 using quasar absorption measurements. Our results give upper limits of x ¯ H I ( z = 6.3 ) < 0.79 ± 0.04 (1σ), x ¯ H I ( z = 6.5 ) < 0.87 ± 0.03 (1σ), and x ¯ H I ( z = 6.7 ) < 0.94 − 0.09 + 0.06 (1σ). The dark pixel fractions at z > 6.1 are consistent with the redshift evolution of the neutral fraction of the IGM derived from Planck 2018.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

(Nearly) Model-independent Constraints on the Neutral Hydrogen Fraction in the Intergalactic Medium at z ∼ 5–7 Using Dark Pixel Fractions in Lyα and Lyβ Forests

Jin

Yang

Fan

et al. 2023

ApJ

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“…The volume averaged H I fractions in the simulations at 𝑧 = 6, 7 and 8 are listed in Table 1. All three models are consistent with existing constraints on ⟨𝑥 HI ⟩ at 𝑧 > 6 and the CMB electron scattering optical depth, but the RT-late model in particular is chosen to match the 𝑧 R required by the large scale fluctuations observed in the Ly𝛼 forest effective optical depth at 𝑧 ≳ 5 (Becker et al 2015b;Kulkarni et al 2019;Keating et al 2020;Zhu et al 2022). We use RT-late for our fiducial reionization model in this work.…”

Section: Hydrodynamical Simulationsmentioning

confidence: 91%

Probing quasar lifetimes with proximate 21-centimetre absorption in the diffuse intergalactic medium at redshifts z ≥ 6

Šoltinský

Bolton

Molaro

et al. 2022

Monthly Notices of the Royal Astronomical Society

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Enhanced ionizing radiation in close proximity to redshift z ≳ 6 quasars creates short windows of intergalactic Lyα transmission blueward of the quasar Lyα emission lines. The majority of these Lyα near-zones are consistent with quasars that have optically/UV bright lifetimes of $t_{\rm Q}\sim 10^{5}-10^{7}\rm \, yr$. However, lifetimes as short as $t_{\rm Q}\lesssim 10^{4}\rm \, yr$ appear to be required by the smallest Lyα near-zones. These short lifetimes present an apparent challenge for the growth of $\sim 10^{9}\rm \, M_{\odot }$ black holes at z ≳ 6. Accretion over longer timescales is only possible if black holes grow primarily in an obscured phase, or if the quasars are variable on timescales comparable to the equilibriation time for ionized hydrogen. Distinguishing between very young quasars and older quasars that have experienced episodic accretion with Lyα absorption alone is challenging, however. We therefore predict the signature of proximate 21-cm absorption around z ≳ 6 radio-loud quasars. For modest pre-heating of intergalactic hydrogen by the X-ray background, where the spin temperature $T_{\rm S} \lesssim 10^{2}\rm \, K$ prior to any quasar heating, we find proximate 21-cm absorption should be observable in the spectra of radio-loud quasars. The extent of the proximate 21-cm absorption is sensitive to the integrated lifetime of the quasar. Evidence for proximate 21-cm absorption from the diffuse intergalactic medium within $2-3\rm \, pMpc$ of a (radio-loud) quasar would be consistent with a short quasar lifetime, $t_{\rm Q}\lesssim 10^{5}\rm \, yr$, and would provide a complementary constraint on models for high redshift black hole growth.

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“…All results shown here adopt our fiducial source scenario. We include measurements from the literature in the left panel (McGreer et al 2015;Greig et al 2016;Greig et al 2019;Davies et al 2018;Mason et al 2018;Mason et al 2019;Wang et al 2020;Yang et al 2020;Greig et al 2022;Zhu et al 2022). All the reionization histories are similar except the Maximum C HII (Δ) case.…”

Section: Sinks Modelsmentioning

confidence: 99%

The Morphology of Reionization in a Dynamically Clumpy Universe

Cain¹,

D’Aloisio²,

Gangolli³

et al. 2022

Preprint

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A recent measurement of the Lyman-limit mean free path at 𝑧 = 6 suggests it may have been very short, motivating a better understanding of the role that ionizing photon sinks played in the reionization process. Accurately modeling the sinks in reionization simulations is challenging because of the large dynamic range required if gas structures on scales ∼ 10 4 − 10 8 𝑀 contributed significant opacity. As a result, there is no consensus on how important the sinks were in shaping reionization's morphology and its observables. We address this question with a recently developed radiative transfer code that includes a dynamical sub-grid model for the sinks based on radiative hydrodynamics simulations. Compared to assuming a fully pressuresmoothed IGM, our dynamical treatment reduces the predicted sizes of ionized bubbles by 10 − 20% under typical assumptions about reionization's sources. Near the midpoint of reionization, the 21 cm power at 𝑘 ∼ 0.1 ℎMpc −1 is reduced by a similar factor. These effects are more modest than the 25 − 45% power suppression resulting from the much higher recombination rate in models that neglect pressure smoothing entirely. Whether the sinks played a significant role in reionization's morphology depends on the nature of its sources. For example, if reionization was driven by bright (𝑀 UV < −17) galaxies, the sinks reduce the large-scale 21 cm power by at most 15%, even if pressure smoothing is neglected. Conveniently, when bright sources contribute significantly, the morphology in our dynamical treatment can be reproduced to high accuracy with a uniform sub-grid clumping factor that yields the same ionizing photon budget. By contrast, if 𝑀 UV ∼ −13 galaxies drove reionization, an accurate model of the sinks' dynamics is more important, with the uniform clumping model erring at the 20% level.

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Long Dark Gaps in the Lyβ Forest at z < 6: Evidence of Ultra-late Reionization from XQR-30 Spectra

Cited by 47 publications

References 63 publications

(Nearly) Model-independent Constraints on the Neutral Hydrogen Fraction in the Intergalactic Medium at z ∼ 5–7 Using Dark Pixel Fractions in Lyα and Lyβ Forests

(Nearly) Model-independent Constraints on the Neutral Hydrogen Fraction in the Intergalactic Medium at z ∼ 5–7 Using Dark Pixel Fractions in Lyα and Lyβ Forests

Probing quasar lifetimes with proximate 21-centimetre absorption in the diffuse intergalactic medium at redshifts z ≥ 6

The Morphology of Reionization in a Dynamically Clumpy Universe

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