The End of Helium Reionization at z~2.7 Inferred from Cosmic Variance in HST/COS HeII Lyman Alpha Absorption Spectra

Abstract

We report on the detection of strongly varying intergalactic HeII absorption in HST/COS spectra of two z~3 quasars. From our homogeneous analysis of the HeII absorption in these and three archival sightlines, we find a marked increase in the mean HeII effective optical depth from tau~1 at z~2.3 to tau>5 at z~3.2, but with a large scatter of 2< tau <5 at 2.7< z <3 on scales of ~10 proper Mpc. This scatter is primarily due to fluctuations in the HeII fraction and the HeII-ionizing background, rather than density variations that are probed by the co-eval HI forest. Semianalytic models of HeII absorption require a strong decrease in the HeII-ionizing background to explain the strong increase of the absorption at z>2.7, probably indicating HeII reionization was incomplete at z>2.7. Likewise, recent three-dimensional numerical simulations of HeII reionization qualitatively agree with the observed trend only if HeII reionization completes at z=2.7 or even below, as suggested by a large tau>3 in two of our five sightlines at z<2.8. By doubling the sample size at 2.7< z <3, our newly discovered HeII sightlines for the first time probe the diversity of the second epoch of reionization when helium became fully ionized.

arXiv comment6 pages, 4 color figures; ApJL in press; One clarification, typo corrections

References in corpus (37)

• Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
• Radiative Transfer in a Clumpy Universe: II. The Utraviolet Extragalactic Background
• Constraining the Evolution of the Ionizing Background and the Epoch of Reionization with z ~ 6 Quasars II: A Sample of 19 Quasars
• Equation of State of the Photoionized Intergalactic Medium
• A New Calculation of the Ionizing Background Spectrum and the Effects of HeII Reionization
• Reionization of the Inhomogeneous Universe
• The thermal history of the intergalactic medium
• Cosmological Reionization by Stellar Sources
• Detection of Extended He II Reionization in the Temperature Evolution of the Intergalactic Medium
• HeII Reionization and its Effect on the IGM
• A Direct Precision Measurement of the Intergalactic Lyman-alpha Opacity at 2<z<4.2
• The Lyman-alpha forest opacity and the metagalactic hydrogen ionization rate at z~2-4
• A Lower Bound on the Cosmic Baryon Density
• A Measurement of Small Scale Structure in the 2.2 < z < 4.2 Lyman-alpha Forest
• Quasars Probing Quasars II: The Anisotropic Clustering of Optically Thick Absorbers around Quasars
• A Study of the Reionization History of Intergalactic Helium with FUSE and VLT
• The Redshift Evolution of the Metagalactic Ionizing Flux Inferred from Metal Line Ratios in the Lyman Forest
• Caught in the act: a helium-reionizing quasar near the line of sight to Q0302-003
• An unbiased measurement of the UV background and its evolution via the proximity effect in quasar spectra
• The History and Morphology of Helium Reionization
• Resolving the high redshift Lyman-alpha forest in smoothed particle hydrodynamics simulations
• The Epoch of Helium Reionization
• Detection of He II reionization in the SDSS quasar sample
• GALEX far-UV color selection of UV-bright high-redshift quasars
• The UV spectrum of HS1700+6416 II. FUSE observations of the HeII Lyman alpha forest
• The transverse proximity effect in spectral hardness on the line of sight towards HE 2347-4342
• Intergalactic HeII absorption towards QSO 1157+3143
• Spectral shape of the UV ionizing background and HeII absorption at redshifts 1.8 < z < 2.9
• The evolution of the helium-ionizing background at z ~ 2-3
• A High Yield of New Sightlines for the Study of Intergalactic Helium: Far-UV-Bright Quasars from SDSS, GALEX, and HST
• He II absorption and the sawtooth spectrum of the cosmic far-UV background
• Patchy He II reionization and the physical state of the IGM
• Large-Scale Fluctuations in the HeII Lyman-alpha Forest and HeII Reionization
• Fluctuations of the intergalactic UV background towards two lines of sight
• The evolution of the Lyman-alpha forest effective optical depth following HeII reionisation
• The impact of spatial fluctuations in the ultra-violet background on intergalactic carbon and silicon
• Ten More New Sightlines for the Study of Intergalactic Helium, and Hundreds of Far-UV-Bright Quasars, from SDSS, GALEX, and HST

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