HeII Ly$\alpha$ Transmission Spikes and Absorption Troughs in Eight High-resolution Spectra Probing the End of HeII Reionization

Abstract

We present statistics of HeII Lya transmission spikes and large-scale absorption troughs using archival high-resolution ($R=\lambda /\Delta \lambda \simeq 12,500$-$18,000$) far-UV spectra of eight HeII-transparent quasars obtained with the Cosmic Origins Spectrograph on the Hubble Space Telescope. The sample covers the redshift range 2.5<z<3.8, thereby probing the rapidly evolving HeII absorption at the end of the HeII reionization epoch. The measured lengths of the troughs decrease dramatically from L>100cMpc at z>3 to L~30cMpc at z~2.7, signaling a significant progression of HeII reionization at these redshifts. Furthermore, unexpectedly long L~65cMpc troughs detected at z~2.9 suggest that the UV background fluctuates at larger scales than predicted by current models. By comparing the measured incidence of transmission spikes to predictions from forward-modeled mock spectra created from the outputs of a (146cMpc)^3 optically thin Nyx hydrodynamical simulation employing different UV background models, we infer the redshift evolution of the HeII photoionization rate ${\Gamma }_{\mathrm{He}\mathrm{II}}(z)$. The photoionization rate decreases with increasing redshift from $\simeq 4.6\times 10^{-15}{\mathrm{s}}^{-1}$ at z~2.6 to $\simeq 1.2\times 10^{-15}{\mathrm{s}}^{-1}$ at z~3.2, in agreement with previous inferences from the HeII effective optical depth, and following expected trends of current models of a fluctuating HeII-ionizing background.

arXiv commentAccepted for publication in ApJ following minor revision (added 2 new figures); 16 pages, 14 figures

References in corpus (71)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• Astropy: A Community Python Package for Astronomy
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• A Unified Approach to the Classical Statistical Analysis of Small Signals
• 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
• An Observational Determination of the Bolometric Quasar Luminosity Function
• Radiative Transfer in a Clumpy Universe: III. The Nature of Cosmological Ionizing Sources
• Reionization of the Inhomogeneous Universe
• The Cosmic Origins Spectrograph
• 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
• 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
• HeII Reionization and its Effect on the IGM
• Evolution of the Intergalactic Opacity: Implications for the Ionizing Background, Cosmic Star Formation, and Quasar Activity
• Evolution of the AGN UV luminosity function from redshift 7.5
• The Lyman-$\alpha$ forest in optically-thin hydrodynamical simulations
• 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
• New Constraints on IGM Thermal Evolution from the Lyα Forest Power Spectrum
• The High-Redshift He II Gunn-Peterson Effect: Implications and Future Prospects
• Resolving the Structure of Ionized Helium in the Intergalactic Medium with the Far Ultraviolet Spectroscopic Explorer
• 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
• Early and Extended Helium Reionization Over More Than 600 Million Years of Cosmic Time
• Caught in the act: a helium-reionizing quasar near the line of sight to Q0302-003
• Approaching Reionization: The Evolution of the Lyman Alpha Forest from Redshifts Four to Six
• The thermal history of the intergalactic medium down to redshift z=1.5: a new curvature measurement
• The End of Helium Reionization at z~2.7 Inferred from Cosmic Variance in HST/COS HeII Lyman Alpha Absorption Spectra
• Glimpsing through the high redshift neutral hydrogen fog
• The History and Morphology of Helium Reionization
• Constraining the reionization history with QSO absorption spectra
• The Epoch of Helium Reionization
• A New Measurement of the Temperature Density Relation of the IGM From Voigt Profile Fitting
• The imprint of inhomogeneous HeII reionization on the HI and HeII Ly-alpha forest
• GALEX far-UV color selection of UV-bright high-redshift quasars
• Chasing the Tail of Cosmic Reionization with Dark Gap Statistics in the Ly$\alpha$ Forest over $5<z<6$
• Towards a Unified Description of the Intergalactic Medium at Redshift z~2.5
• 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
• GALEX Diffuse Observations of the Sky: The Data
• Observations of the Lyman series forest towards the redshift 7.1 quasar ULAS J1120+0641
• Statistical Detection of the HeII Transverse Proximity Effect: Evidence for Sustained Quasar Activity for $>$25 Million Years
• Large scale simulations of H and He reionization and heating driven by stars and more energetic sources
• The Evolution of the HeII-Ionizing Background at Redshifts 2.3<z<3.8 Inferred from a Statistical Sample of 24 HST/COS HeII Ly$\alpha$ Absorption Spectra
• Cosmic Reionization On Computers. Properties of the Post-reionization IGM
• Helium Reionization Simulations. II. Signatures of Quasar Activity on the IGM
• He II Proximity Effect and the Lifetime of Quasars
• Evidence for Short $\sim 1$ Myr Lifetimes from the He II Proximity Zones of $z\sim 4$ Quasars
• The Implications of Gunn-Peterson Troughs in the HeII Lyman-alpha Forest
• A Statistical Analysis of Intergalactic Medium Transmission Approaching Reionization
• AGN-driven helium reionization and the incidence of extended HeIII regions at redshift z>3
• A High Yield of New Sightlines for the Study of Intergalactic Helium: Far-UV-Bright Quasars from SDSS, GALEX, and HST
• HST/COS Observations of Thirteen New He II Quasars
• Large-Scale Fluctuations in the HeII Lyman-alpha Forest and HeII Reionization
• Anomaly in the Opacity of the Post-Reionization Intergalactic Medium in the Ly$\alpha$ and Ly$\beta$ Forest
• A self-consistent 3D model of fluctuations in the helium-ionizing background
• Modeling the HeII Transverse Proximity Effect: Constraints on Quasar Lifetime and Obscuration
• Fluctuations of the intergalactic UV background towards two lines of sight
• The case against large intensity fluctuations in the z ~ 2.5 HeII Lyman-alpha forest
• How to Search for Islands of Neutral Hydrogen in the $z\sim 5.5$ IGM
• New Evidence for Extended HeII Reionization at z>3.5 from HeII Lyman Alpha and Beta Transmission Spikes
• Constraining the Tail-End of Reionization Using Lyman-$\alpha$ Transmission Spikes
• Ten More New Sightlines for the Study of Intergalactic Helium, and Hundreds of Far-UV-Bright Quasars, from SDSS, GALEX, and HST
• Dating individual quasars with the HeII proximity effect
• The influence of metagalactic ultra-violet background fluctuations on the high-redshift Ly$\alpha$ forest
• A tale of seven narrow spikes and a long trough: constraining the timing of the percolation of HII bubbles at the tail-end of reionization with ULAS J1120+0641
• The evolution of the low-density HI intergalactic medium from z=3.6 to 0: Data, transmitted flux and HI column density

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