(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

Autor: Xiangyu Jin, Jinyi Yang, Xiaohui Fan, Feige Wang, Eduardo Bañados, Fuyan Bian, Frederick B. Davies, Anna-Christina Eilers, Emanuele Paolo Farina, Joseph F. Hennawi, Fabio Pacucci, Bram Venemans, Fabian Walter
Jazyk: angličtina
Rok vydání: 2023
Předmět:
Zdroj: The Astrophysical Journal, Vol 942, Iss 2, p 59 (2023)
Druh dokumentu: article
ISSN: 1538-4357
38081520
DOI: 10.3847/1538-4357/aca678
Popis: 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 ( ${\overline{x}}_{{\rm{H}}\,{\rm\small{I}}}\lesssim {10}^{-3}$ ) or close to unity ( ${\overline{x}}_{{\rm{H}}\,{\rm\small{I}}}\sim 1$ ). 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 ${\overline{x}}_{{\rm{H}}\,{\rm\small{I}}}$ 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 Ly α and Ly β 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 ${\overline{x}}_{{\rm{H}}\,{\rm\small{I}}}(z=6.3)\lt 0.79\pm 0.04$ (1 σ ), ${\overline{x}}_{{\rm{H}}\,{\rm\small{I}}}(z=6.5)\lt 0.87\pm 0.03$ (1 σ ), and ${\overline{x}}_{{\rm{H}}\,{\rm\small{I}}}(z=6.7)\lt {0.94}_{-0.09}^{+0.06}$ (1 σ ). 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.
Databáze: Directory of Open Access Journals
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