Cosmic Reionization on Computers: Physical Origin of Long Dark Gaps in Quasar Absorption Spectra

Abstract

I explore the properties of "dark gaps" - regions in quasar absorption spectra without significant transmission - with several simulations from the Cosmic Reionization On Computers (CROC) project. CROC simulations in largest available boxes (120 cMpc) come close to matching both the distribution of mean opacities and the frequency of dark gaps, but alas not in the same model: the run that matches the mean opacities fails to contain enough dark gaps and vice versa.:( Never-the-less, the run that matches the dark gap distributions serves as a counter-example to claims in the literature that the dark gap statistics requires a late end to reionization - in that run reionization ends at z=6.7 (likely too early). While multiple factors contribute to the frequency of large dark gaps in the simulations, the primary factor that controls the overall shape of the dark gap distribution is the ionization level in voids - the lowest density regions produce the highest transmission spikes that terminate long gaps. As the result, the dark gap distribution correlates strongly with the fraction of the spectrum above the gap detection threshold, the observed distribution is matched by the simulation in which this fraction is 2%. Hence, the gap distribution by itself does not constrain the timing of reionization.

arXiv commentSubmitted to ApJ

References in corpus (30)

• Constraining the Evolution of the Ionizing Background and the Epoch of Reionization with z ~ 6 Quasars II: A Sample of 19 Quasars
• A hierarchy of voids: Much ado about nothing
• Evidence of patchy hydrogen reionization from an extreme Ly$\alpha$ trough below redshift six
• Cosmological Reionization by Stellar Sources
• New constraints on Lyman-α opacity with a sample of 62 quasars at z > 5.7
• Initial conditions to cosmological N-body simulations, or how to run an ensemble of simulations
• Cosmic Reionization On Computers I. Design and Calibration of Simulations
• The Opacity of the Intergalactic Medium Measured Along Quasar Sightlines at $z\sim 6$
• The abundance of voids and the excursion set formalism
• Measurements of the z ~ 6 Intergalactic Medium Optical Depth and Transmission Spikes Using a New z > 6.3 Quasar Sample
• The THESAN project: properties of the intergalactic medium and its connection to Reionization-era galaxies
• Observing the tail of reionization: neutral islands in the $z=5.5$ Lyman-$\alpha$ Forest
• Cosmology with Void-Galaxy Correlations
• Large-Scale Clustering of Cosmic Voids
• Implementing the DC Mode in Cosmological Simulations with Supercomoving Variables
• Chasing the Tail of Cosmic Reionization with Dark Gap Statistics in the Ly$\alpha$ Forest over $5<z<6$
• The THESAN project: predictions for multi-tracer line intensity mapping in the epoch of reionization
• The evolution of neutral gas in damped Lyman $\alpha$ systems from the XQ-100 survey
• Reionization, SLOAN, and WMAP: is the Picture Consistent?
• Generating Cosmological Gaussian Random Fields
• Cosmic Reionization On Computers. Properties of the Post-reionization IGM
• Excursion Sets and Non-Gaussian Void Statistics
• Hunting high and low: Disentangling primordial and late-time non-Gaussianity with cosmic densities in spheres
• Testing spherical evolution for modelling void abundances
• Large Scale Anisotropic Bias from Primordial non-Gaussianity
• Sub-damped Lyman alpha systems in the XQ-100 survey I -- Identification and contribution to the cosmological HI budget
• The scale-dependent signature of primordial non-Gaussianity in the large-scale structure of cosmic reionization
• Cosmic Reionization On Computers: The Galaxy-Halo Connection between $5\le z\le 10$
• Cosmic Reionization On Computers. Ultraviolet Continuum Slopes and Dust Opacities in High Redshift Galaxies
• Analysis of methods for detecting the proximity effect in quasar spectra

Cited by in corpus (4)

• Damping Wing-Like Features in the Stacked Ly$\alpha$ Forest: Potential Neutral Hydrogen Islands at $z<6$
• Reionization relics in the cross-correlation between the Ly$\alpha$ forest and 21 cm intensity mapping in the post-reionization era
• On the Physical Nature of Ly$\alpha$ Transmission Spikes in High Redshift Quasar Spectra
• Uncertainty-Aware Neural Networks for Fuzzy Dark Matter Model Selection from \texorpdfstring{$x_{\mathrm{HI}}$}{x_HI} Measurements