Astronomy and Astrophysics – Astrophysics
Scientific paper
Jun 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992apj...392...15m&link_type=abstract
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 392, no. 1, June 10, 1992, p. 15-22.
Astronomy and Astrophysics
Astrophysics
56
Absorption Spectra, Helium Ions, Lyman Alpha Radiation, Red Shift, Background Radiation, Dark Matter, Molecular Clouds, Quasars
Scientific paper
Sources and sinks of radiation are used to model the evolution of the metagalactic ionizing background radiation field. It is shown that, if the comoving number density of quasars approached constancy at high redshift, as suggested by some recent observations, the observed ionizing background might possibly have been produced by the observed quasars alone. Consideration is also given to the UV radiation from decaying neutrons proposed by Sciama (1990), as an extra possible source. If is found that, if the background spectrum were as soft as in the Sciama scenario, the observed Ly-alpha clouds would contain detectable amounts of neutral helium, producing an 'He I forest' almost as dense as the hydrogen forest, due to the 584-A transition 1s-squared-1s2p. It is argued that observations of the Ly-alpha forest contradict the Sciama hypothesis.
Miralda-Escude' Jordi
Ostriker Jeremiah P.
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