Studying dark gaps in Ly-$\alpha$ forest transmission with large reionization simulations

Abstract

The physical conditions of the intergalactic medium (IGM) during the final stages of cosmic reionization ($z\sim 5.0-6.0$) are not yet fully understood. Recent reports of unexpectedly large-scale ($\ge 150h^{-1}\mathrm{cMpc}$) correlation in Ly-$\alpha$ transmission flux using extended XQR-30 quasar spectra pose interesting challenges on the reionization end stages. In this work, we investigate the Ly-$\alpha$ forest dark-gap distribution (defined as regions with transmitted flux below 0.05) as another sensitive tracer of the IGM, using an efficient, large-volume ($\sim 1\mathrm{Gpc}$) simulation framework. By constructing a suite of physically motivated model variants (i.e, varying the reionization redshift, IGM temperature, and ionizing-photon mean free path), we generate synthetic sightlines and compare their predicted cumulative distribution of dark gaps with that of observed spectra (at redshift intervals of $\Delta z=0.2$). We find that most of the models achieve qualitatively consistent agreement with the data. The scenario involving a slightly later reionization completion ($z\sim 5.4$) provides the closest match, while a short constant mean free path model is disfavored by the data at lower redshifts. These findings give qualitative support for the emerging scenario of reionization end extending to $z\le 5.7$, although they can not rule out a slightly early reionization with enhanced post-ionization ultraviolet (UV) background fluctuations. A similar conclusion arises from the redshift distribution of long dark gap ($L\ge 30h^{-1}\mathrm{cMpc}$) fraction. However, the model variants are still not able to reproduce the observed strong flux correlations at unusually large scales, which remains open for further investigations.

arXiv commentAccepted in A&A, 9 pages, 6 figures (+ Appendices)

References in corpus (35)

• Constraining the Evolution of the Ionizing Background and the Epoch of Reionization with z ~ 6 Quasars II: A Sample of 19 Quasars
• In the Beginning: The First Sources of Light and the Reionization of the Universe
• 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
• Evidence of patchy hydrogen reionization from an extreme Ly$\alpha$ trough below redshift six
• The Universe is Reionizing at z~7: Bayesian Inference of the IGM Neutral Fraction Using Ly$\alpha$ Emission from Galaxies
• The Evolution of the Intergalactic Medium
• 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
• Nyx: A Massively Parallel AMR Code for Computational Cosmology
• 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
• 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
• Constraints on reionisation from the z=7.5 QSO ULASJ1342+0928
• The mean free path of ionizing photons at 5 < z < 6: evidence for rapid evolution near reionization
• Large fluctuations in the hydrogen-ionizing background and mean free path following the epoch of reionization
• Probing the thermal state of the intergalactic medium at $z>5$ with the transmission spikes in high-resolution Ly$\alpha$ forest spectra
• Observing the tail of reionization: neutral islands in the $z=5.5$ Lyman-$\alpha$ Forest
• Large Opacity Variations in the High-Redshift Lyman-alpha Forest: the Signature of Relic Temperature Fluctuations from Patchy Reionization
• Glimpsing through the high redshift neutral hydrogen fog
• (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
• 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
• XQR-30: the ultimate XSHOOTER quasar sample at the reionization epoch
• Chasing the Tail of Cosmic Reionization with Dark Gap Statistics in the Ly$\alpha$ Forest over $5<z<6$
• Damping Wing-Like Features in the Stacked Ly$\alpha$ Forest: Potential Neutral Hydrogen Islands at $z<6$
• Constraining the second half of reionization with the Lyman-$\beta$ forest
• Damping wings in the Lyman-α forest: a model-independent measurement of the neutral fraction at 5.4<z<6.1
• Cosmic Reionization On Computers. Properties of the Post-reionization IGM
• AMBER: A Semi-numerical Abundance Matching Box for the Epoch of Reionization
• A Short Introduction to Reionization Physics
• Probing the thermal history during reionization using a semi-numerical photon-conserving code SCRIPT
• Updated dark pixel fraction constraints on reionization's end from the Lyman-series forests of XQR-30
• Efficient Modelling of Lyman-α opacity fluctuations during late reionization epoch
• Measuring the IGM correlation length at 5<z<6.1: a fast change at the end of Reionization