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The evolution of the diffuse cosmic ultraviolet background constrained by the Hubble Space Telescope observations of 3C 273Results are presented of recent HST UV spectroscopy of 3C 273, which revealed more low-redshift Lyman-alpha absorption lines (IGM clouds) than expected from the extrapolation from high-redshift (not less than 1.6) observations. It is shown on the basis of the standard pressure confined cloud model of the Lyman-alpha forest that this result indicates a sharp drop in the diffuse cosmic UV background from 2 to 0 redshift. It is predicted that the H I optical depth will drop slowly or perhaps even increase with decreasing redshift at less than 2 redshift. The implied constraints on the density and pressure of the diffuse IGM at 0 redshift are also derived. The inferred evolution of the diffuse UV flux bears a striking resemblance to the most recent direct determinations of the volume emissivity of the quasar population.
Document ID
19920030061
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Ikeuchi, Satoru
(National Astronomical Observatory Mitaka, Japan)
Turner, Edwin L.
(Princeton University Observatory, NJ, United States)
Date Acquired
August 15, 2013
Publication Date
November 1, 1991
Publication Information
Publication: Astrophysical Journal, Part 2 - Letters
Volume: 381
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
92A12685
Funding Number(s)
CONTRACT_GRANT: NAGW-2448
Distribution Limits
Public
Copyright
Other

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