{"paper":{"title":"Early and Extended Helium Reionization Over More Than 600 Million Years of Cosmic Time","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"","cross_cats":[],"primary_cat":"astro-ph.CO","authors_text":"G\\'abor Worseck (UCO/Lick Observatory & MPIA), Joseph F. Hennawi (MPIA), J. Xavier Prochaska (UCO/Lick Observatory), Matthew McQuinn (University of Washington)","submitted_at":"2014-05-28T21:38:51Z","abstract_excerpt":"We measure the effective optical depth of HeII Ly\\alpha\\ absorption \\tau$_\\mathsf{eff,HeII}$ at 2.3<z<3.5 in 17 UV-transmitting quasars observed with UV spectrographs on the Hubble Space Telescope (HST). The median \\tau$_\\mathsf{eff,HeII}$ values increase gradually from 1.95 at z=2.7 to 5.17 at z=3.4, but with a strong sightline-to-sightline variance. Many $\\simeq$35 comoving Mpc regions of the z>3 intergalactic medium (IGM) remain transmissive (\\tau$_\\mathsf{eff,HeII}$<4), and the gradual trend with redshift appears consistent with density evolution of a fully reionized IGM. These modest opti"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"1405.7405","kind":"arxiv","version":2},"verdict":{"id":null,"model_set":{},"created_at":null,"strongest_claim":"","one_line_summary":"","pipeline_version":null,"weakest_assumption":"","pith_extraction_headline":""},"references":{"count":0,"sample":[],"resolved_work":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","internal_anchors":0},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}