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Title: Carbon ionization states and the cosmic far-UV background with He II absorption
Authors: Vasiliev, Evgenii O.
Sethi, S.K.
Nath, Biman B.
Keywords: cosmology: theory
diffuse radiation
intergalactic medium
quasars: general
Issue Date: 28-Jul-2010
Publisher: IOP Publishing Ltd.
Citation: Astrophysical Journal, 2010, Vol. 719, p1343
Abstract: We constrain the spectrum of the cosmic ultraviolet background radiation by fitting the observed abundance ratios of carbon ions at z ~ 2-3 with those expected from different models of the background radiation. We use the recently calculated modulation of the background radiation between 3 and 4 Ryd due to resonant line absorption by intergalactic He II and determine the ratios of C III to C IV expected at these redshifts, as functions of metallicity, gas density, and temperature. Our analysis of the observed ratios shows that "delayed reionization" models, which assume a large fraction of He II at z ~ 3, are not favored by data. Our results suggest that He II reionization was inhomogeneous, consistent with the predictions from recent simulations.
Description: Restricted Access. An open-access version is available at (one of the alternative locations)
ISSN: 1538-4357-(Online)
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Copyright: 2010 IOP Publishing for the American Astronomical Society
Appears in Collections:Research Papers (A&A)

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