The Intergalactic Lyα Opacity at 2 ≤ z ≤ 4.2: Implications for the Ionizing Background, Cosmic Star Formation, and Quasar Activity

Claude Andre Faucher Giguere, Adam Lidz, Matias Zaldarriaga

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

We investigate the implications of our measurement of the Lyman-α forest opacity at redshifts 2 ≤ z ≤ 4.2 from a sample of 86 high-resolution quasar spectra for the evolution of the cosmic ultraviolet luminosity density and its sources. The derived hydrogen photoionization rate Γ ≈ (0.5 ± 0.1) × 10−12 s−1 is remarkably flat over this redshift range. Because the quasar luminosity function is strongly peaked near z ∼ 2, the lack of redshift evolution indicates that star-forming galaxies likely dominate the photoionization rate at z ≥ 3, and possibly at all redshifts probed. A star formation history peaking at redshift z = 5 − 6, as in the theoretical model of Hernquist & Springel, appears favored over the current state-of-the-art observational fit by Hopkins & Beacom, which peaks at z = 2 − 3. The increasing dominance of stellar emission toward high redshifts indicate that galaxies likely reionized the universe.
Original languageEnglish (US)
Title of host publicationPanoramic Views of Galaxy Formation and Evolution
Subtitle of host publicationProceedings of the 1st Subaru International Conference
EditorsTadayuki Komada, Toru Yamada, Kentaro Aoki
PublisherAstronomical Society of the Pacific
Pages186-189
Number of pages4
ISBN (Electronic)978-1-58381-669-1
ISBN (Print)978-1-58381-668-4
StatePublished - 2008

Publication series

NameAstronomical Society of the Pacific conference series
Volume399

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