Long Dark Gaps in the Ly$\beta$ Forest at $z<6$: Evidence of Ultra Late Reionization from XQR-30 Spectra

Abstract

We present a new investigation of the intergalactic medium (IGM) near reionization using dark gaps in the Lyman-$\beta$ (Ly$\beta$) forest. With its lower optical depth, Ly$\beta$ offers a potentially more sensitive probe to any remaining neutral gas compared to commonly used Ly$\alpha$ line. We identify dark gaps in the Ly$\beta$ forest using spectra of 42 QSOs at $z_{\mathrm{em}}>5.5$, including new data from the XQR-30 VLT Large Programme. Approximately $40\%$ of these QSO spectra exhibit dark gaps longer than $10h^{-1}\mathrm{Mpc}$ at $z\simeq 5.8$. By comparing the results to predictions from simulations, we find that the data are broadly consistent both with models where fluctuations in the Ly$\alpha$ forest are caused solely by ionizing ultraviolet background (UVB) fluctuations and with models that include large neutral hydrogen patches at $z<6$ due to a late end to reionization. Of particular interest is a very long ($L=28h^{-1}\mathrm{Mpc}$) and dark (${\tau }_{\mathrm{eff}}\gtrsim 6$) gap persisting down to $z\simeq 5.5$ in the Ly$\beta$ forest of the $z_{}=5.85$ QSO PSO J025$-$11. This gap may support late reionization models with a volume-weighted average neutral hydrogen fraction of $⟨x_{\mathrm{HI}}⟩\gtrsim 5\%$ by $z=5.6$. Finally, we infer constraints on $⟨x_{\mathrm{HI}}⟩$ over $5.5\lesssim z\lesssim 6.0$ based on the observed Ly$\beta$ dark gap length distribution and a conservative relationship between gap length and neutral fraction derived from simulations. We find $⟨x_{\mathrm{HI}}⟩\le 0.05$, 0.17, and 0.29 at $z\simeq 5.55$, 5.75, and 5.95, respectively. These constraints are consistent with models where reionization ends significantly later than $z=6$.

arXiv comment17 pages, 13 figures, accepted for publication in ApJ. The Figure set and machine readable table are available at https://ydzhuastro.github.io/lyb.html

References in corpus (58)

• Astropy: A Community Python Package for Astronomy
• The NumPy array: a structure for efficient numerical computation
• Planck 2013 results. XVI. Cosmological parameters
• Constraining the Evolution of the Ionizing Background and the Epoch of Reionization with z ~ 6 Quasars II: A Sample of 19 Quasars
• Radiative transfer in a clumpy universe: IV. New synthesis models of the cosmic UV/X-ray background
• X-shooter, the new wide band intermediate resolution spectrograph at the ESO Very Large Telescope
• An 800-million-solar-mass black hole in a significantly neutral Universe at redshift 7.5
• Model-independent evidence in favor of an end to reionization by z~6
• Evidence of patchy hydrogen reionization from an extreme Ly$\alpha$ trough below redshift six
• ESI, a new Keck Observatory echellette spectrograph and imager
• 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
• Quantitative Constraints on the Reionization History from the IGM Damping Wing Signature in Two Quasars at z > 7
• Hydrogen reionisation ends by $z=5.3$: Lyman-$\alpha$ optical depth measured by the XQR-30 sample
• Large Lyman-alpha opacity fluctuations and low CMB tau in models of late reionization with large islands of neutral hydrogen extending to z<5.5
• Inferences on the Timeline of Reionization at z~8 From the KMOS Lens-Amplified Spectroscopic Survey
• New constraints on Lyman-α opacity with a sample of 62 quasars at z > 5.7
• 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
• Consistent modelling of the meta-galactic UV background and the thermal/ionization history of the intergalactic medium
• Long troughs in the Lyman-$\alpha$ forest below redshift 6 due to islands of neutral hydrogen
• The Sherwood simulation suite: overview and data comparisons with the Lyman-alpha forest at redshifts 2 < z < 5
• 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 $z\sim 6$
• Revealing reionization with the thermal history of the intergalactic medium: new constraints from the Lyman-$\alpha$ flux power spectrum
• Texas Spectroscopic Search for Ly$\alpha$ Emission at the End of Reionization III. the Ly$\alpha$ Equivalent-width Distribution and Ionized Structures at $z>7$
• Probing the thermal state of the intergalactic medium at $z>5$ with the transmission spikes in high-resolution Ly$\alpha$ forest spectra
• Measurements of the z ~ 6 Intergalactic Medium Optical Depth and Transmission Spikes Using a New z > 6.3 Quasar Sample
• Reionization and galaxy inference from the high-redshift Lyα forest
• The Impact of the First Galaxies on Cosmic Dawn and Reionization
• Observing the tail of reionization: neutral islands in the $z=5.5$ Lyman-$\alpha$ Forest
• Approaching Reionization: The Evolution of the Lyman Alpha Forest from Redshifts Four to Six
• The first (nearly) model-independent constraint on the neutral hydrogen fraction at z~5--6
• A consistent and robust measurement of the thermal state of the IGM at $2\le z\le 4$ from a large sample of Ly$\alpha$ forest spectra: Evidence for late and rapid HeII reionization
• Detecting and Characterizing Young Quasars I: Systemic Redshifts and Proximity Zones Measurements
• Glimpsing through the high redshift neutral hydrogen fog
• IGM damping wing constraints on reionisation from covariance reconstruction of two $z\gtrsim 7$ QSOs
• Evidence for Large-Scale Fluctuations in the Metagalactic Ionizing Background Near Redshift Six
• SpectRes: A Fast Spectral Resampling Tool in Python
• Constraining the Topology of Reionization Through Lyman-alpha Absorption
• The Evolution of O I over 3.2 < z < 6.5: Reionization of the Circumgalactic Medium
• Predicting Quasar Continua Near Lyman-$\alpha$ with Principal Component Analysis
• Chasing the Tail of Cosmic Reionization with Dark Gap Statistics in the Ly$\alpha$ Forest over $5<z<6$
• LAGER Ly$\alpha$ Luminosity Function at $z\sim 7$, Implications for Reionization
• A short mean free path at $z=6$ favors late and rapid reionization by faint galaxies
• The Ly$\alpha$ Luminosity Function and Cosmic Reionization at $z\sim$ 7.0: a Tale of Two LAGER Fields
• Studying the Lyman-$\alpha$ optical depth fluctuations at $z\sim 5.5$ using fast semi-numerical methods
• Modelling the observed luminosity function and clustering evolution of Lyman-$\alpha$ emitters: growing evidence for late reionization
• Inference of the optical depth to reionization from low multipole temperature and polarisation Planck data
• A comparison of quasar emission reconstruction techniques for $z\ge 5.0$ Lyman-$\alpha$ and Lyman-$\beta$ transmission
• Constraining the second half of reionization with the Lyman-$\beta$ forest
• Cosmic Reionization On Computers. Properties of the Post-reionization IGM
• The Predicament of Absorption-Dominated Reionization: Increased Demands on Ionizing Sources
• Determining the Nature of Late Gunn-Peterson Troughs with Galaxy Surveys
• Evidence for a highly opaque large-scale galaxy void at the end of reionization
• Constraints on the End of Reionization from the Density Fields Surrounding Two Highly Opaque Quasar Sightlines
• A Statistical Analysis of Intergalactic Medium Transmission Approaching Reionization
• Anomaly in the Opacity of the Post-Reionization Intergalactic Medium in the Ly$\alpha$ and Ly$\beta$ Forest

Cited by in corpus (37)

• EIGER I. a large sample of [OIII]-emitting galaxies at $5.3<z<6.9$ and direct evidence for local reionization by galaxies
• (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
• XQR-30: the ultimate XSHOOTER quasar sample at the reionization epoch
• Inferring the IGM Neutral Fraction at z ~ 6-8 with Low-Luminosity Lyman Break Galaxies
• Chronicling the reionization history at $6\lesssim z\lesssim 7$ with emergent quasar damping wings
• Damping Wing-Like Features in the Stacked Ly$\alpha$ Forest: Potential Neutral Hydrogen Islands at $z<6$
• Damping wings in the Lyman-α forest: a model-independent measurement of the neutral fraction at 5.4<z<6.1
• The XQR-30 Metal Absorber Catalog: 778 Absorption Systems Spanning 2 < z < 6.5
• The fraction and kinematics of broad absorption line quasars across cosmic time
• SPICE: the connection between cosmic reionisation and stellar feedback in the first galaxies
• PRIYA: A New Suite of Lyman-alpha Forest Simulations for Cosmology
• Examining the Decline in the C IV Content of the Universe over 4.3 < z < 6.3 using the E-XQR-30 Sample
• The Morphology of Reionization in a Dynamically Clumpy Universe
• LIMFAST. I. A Semi-Numerical Tool for Line Intensity Mapping
• Late-end reionization with ATON-HE: towards constraints from Lyman-$\alpha$ emitters observed with JWST
• Optical depth to reionization from perturbative 21cm clustering
• Lyman-alpha Emitters in Ionized Bubbles: Constraining the Environment and Ionized Fraction
• The impact of faint AGN discovered by JWST on reionization
• Probing quasar lifetimes with proximate $21$-centimetre absorption in the diffuse intergalactic medium at redshifts $z\ge 6$
• Emission-line Stacking of 21cm Intensity Maps with MeerKLASS: Inference Pipeline and Application to the L-band Deep-field Data
• Probing patchy reionisation with JWST: IGM opacity constraints from the Lyman-$\alpha$ forest of galaxies in legacy extragalactic fields
• Galaxy Formation and Symbiotic Evolution with the Inter-Galactic Medium in the Age of ELT-ANDES
• The Lyman-limit photon mean free path at the end of late reionisation in the Sherwood-Relics simulations
• Studying the Multi-frequency Angular Power Spectrum of the Cosmic Dawn 21-cm Signal
• Photometric IGM tomography with Subaru/HSC: the large-scale structure of Ly$\alpha$ emitters and IGM transmission in the COSMOS field at $z\sim 5$
• Prospects of a statistical detection of the 21-cm forest and its potential to constrain the thermal state of the neutral IGM during reionization
• Impact of the primordial fluctuation power spectrum on the reionization history
• Galaxy formation with wave/fuzzy dark matter: The core-halo structure and the solitonic imprint
• Ly$\alpha$ Emission from [OIII] Emitters Near Reionization: The role of environment in galaxy Ly$\alpha$ detection
• Global 21 cm signal: a promising probe of primordial features
• Reionizing islands with inhomogeneous recombinations
• Efficient Modelling of Lyman-α opacity fluctuations during late reionization epoch
• Mapping neutral islands during end stages of reionization with photometric intergalactic medium tomography
• Imaging reionization's last phases with I-front Lyman-$\alpha$ emissions
• Quantifying Lyman-$\alpha$ emissions from reionization fronts
• Efficient neutral-IGM inference from noisy 21-cm forest spectra with latent-space U-Net encoding and XGBoost
• Quantifying and mitigating the effect of snapshot interval in light-cone Epoch of Reionization 21-cm simulations