(Nearly) Model-Independent Constraints on the Neutral Hydrogen Fraction in the Intergalactic Medium at $z\sim 5-7$ Using Dark Pixel Fractions in Ly$\alpha$ and Ly$\beta$ Forests

Abstract

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 $z\sim 5.5$. 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 (${\bar{x}}_{\mathrm{HI}}\lesssim 10^{-3}$) or close to unity (${\bar{x}}_{\mathrm{HI}}\sim 1$). 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 ${\bar{x}}_{\mathrm{HI}}$ at $z\sim 5.1-6.8$, 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 Lyman $\alpha$ (Ly$\alpha$) and Lyman $\beta$ (Ly$\beta$) 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 $z\sim 6.2-6.8$ using quasar absorption measurements. Our results give upper limits of ${\bar{x}}_{\mathrm{HI}}(z=6.3)<0.79\pm 0.04$ (1$\sigma$), ${\bar{x}}_{\mathrm{HI}}(z=6.5)<0.87\pm 0.03$ (1$\sigma$), and ${\bar{x}}_{\mathrm{HI}}(z=6.7)<0.94_{-0.09}^{+0.06}$ (1$\sigma$). The dark pixel fractions at $z>6.1$ are consistent with the redshift evolution of the neutral fraction of the IGM derived from the Planck 2018.

arXiv comment13 pages, 6 figures, 2 tables, accepted for publication in ApJ

References in corpus (50)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• Astropy: A Community Python Package for Astronomy
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• A luminous quasar at a redshift of z = 7.085
• Constraining the Evolution of the Ionizing Background and the Epoch of Reionization with z ~ 6 Quasars II: A Sample of 19 Quasars
• An 800-million-solar-mass black hole in a significantly neutral Universe at redshift 7.5
• Cosmic Reionization and Early Star-Forming Galaxies: A Joint Analysis of New Constraints from Planck and Hubble Space Telescope
• Model-independent evidence in favor of an end to reionization by z~6
• Keck Spectroscopy of Faint 3<z<7 Lyman Break Galaxies: - I. New constraints on cosmic reionisation from the luminosity and redshift-dependent fraction of Lyman-alpha emission
• Evidence of patchy hydrogen reionization from an extreme Ly$\alpha$ trough below redshift six
• Reionization of the Intergalactic Medium and the Damping Wing of the Gunn-Peterson Trough
• The Universe is Reionizing at z~7: Bayesian Inference of the IGM Neutral Fraction Using Ly$\alpha$ Emission from Galaxies
• Pōniuā'ena: A Luminous $z=7.5$ Quasar Hosting a 1.5 Billion Solar Mass Black Hole
• Conditions for Reionizing the Universe with A Low Galaxy Ionizing Photon Escape Fraction
• Quantitative Constraints on the Reionization History from the IGM Damping Wing Signature in Two Quasars at z > 7
• Rapid Reionization by the Oligarchs: The Case for Massive, UV-Bright, Star-Forming Galaxies with High Escape Fractions
• Spectroscopic confirmation of z~7 LBGs: probing the earliest galaxies and the epoch of reionization
• Line Emitting Galaxies Beyond a Redshift of 7: An Improved Method for Estimating the Evolving Neutrality of the Intergalactic Medium
• Inferences on the Timeline of Reionization at z~8 From the KMOS Lens-Amplified Spectroscopic Survey
• Systematic Identification of LAEs for Visible Exploration and Reionization Research Using Subaru HSC (SILVERRUSH). I. Program Strategy and Clustering Properties of ~2,000 Lya Emitters at z=6-7 over the 0.3-0.5 Gpc${}^2$ Survey Area
• New constraints on Lyman-α opacity with a sample of 62 quasars at z > 5.7
• The Giant Gemini GMOS survey of z>4.4 quasars - I. Measuring the mean free path across cosmic time
• A Significantly Neutral Intergalactic Medium Around the Luminous z=7 Quasar J0252-0503
• Constraining the neutral fraction of hydrogen in the IGM at redshift 7.5
• Measurements of the UV background at 4.6 < z < 6.4 using the quasar proximity effect
• Accelerated Evolution of Ly$\alpha$ Luminosity Function at $\text{z}\gtrsim 7$ Revealed by the Subaru Ultra-Deep Survey for Ly$\alpha$ Emitters at $\text{z}=7.3$
• Constraints on reionisation from the z=7.5 QSO ULASJ1342+0928
• The identification of z-dropouts in Pan-STARRS1: three quasars at 6.5<z<6.7
• The mean free path of ionizing photons at 5 < z < 6: evidence for rapid evolution near reionization
• The Opacity of the Intergalactic Medium Measured Along Quasar Sightlines at $z\sim 6$
• HST-COS Observations of AGN. I. Ultraviolet Composite Spectra of the Ionizing Continuum and Emission Lines
• Texas Spectroscopic Search for Ly$\alpha$ Emission at the End of Reionization III. the Ly$\alpha$ Equivalent-width Distribution and Ionized Structures at $z>7$
• Evidence of Gunn-Peterson damping wings in high-z quasar spectra: strengthening the case for incomplete reionization
• Measurements of the z ~ 6 Intergalactic Medium Optical Depth and Transmission Spikes Using a New z > 6.3 Quasar Sample
• Was reionization complete by z ~ 5-6?
• Observing the tail of reionization: neutral islands in the $z=5.5$ Lyman-$\alpha$ Forest
• Lyα emission line reconstruction for high-$z$ QSOs
• Ionization near-zones associated with quasars at z ~ 6
• The first (nearly) model-independent constraint on the neutral hydrogen fraction at z~5--6
• Long Dark Gaps in the Ly$\beta$ Forest at $z<6$: Evidence of Ultra Late Reionization from XQR-30 Spectra
• IGM damping wing constraints on reionisation from covariance reconstruction of two $z\gtrsim 7$ QSOs
• The Evolution of the Lyman-Alpha Luminosity Function During Reionization
• Chasing the Tail of Cosmic Reionization with Dark Gap Statistics in the Ly$\alpha$ Forest over $5<z<6$
• CHORUS II. Subaru/HSC Determination of the Ly$\alpha$ Luminosity Function at $z=7.0$: Constraints on Cosmic Reionization Model Parameter
• A comparison of quasar emission reconstruction techniques for $z\ge 5.0$ Lyman-$\alpha$ and Lyman-$\beta$ transmission
• Observations of the Lyman series forest towards the redshift 7.1 quasar ULAS J1120+0641
• Cosmic Microwave Background Constraints in Light of Priors Over Reionization Histories
• Anomaly in the Opacity of the Post-Reionization Intergalactic Medium in the Ly$\alpha$ and Ly$\beta$ Forest

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• Nearest Neighbour-Based Statistics for 21cm-Galaxy Cross-Correlations in the Epoch of Reionization
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