Astronomy and Astrophysics – Astronomy
Scientific paper
Apr 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992apj...389l...1m&link_type=abstract
Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X), vol. 389, April 10, 1992, p. L1-L4.
Astronomy and Astrophysics
Astronomy
122
Background Radiation, Intergalactic Media, Quasars, Red Shift, Ultraviolet Radiation, Absorption Spectra, Luminosity, Lyman Alpha Radiation, Sky Surveys (Astronomy)
Scientific paper
The quasar luminosity function and its evolution are used to estimate the integrated UV background from observed QSOs as a function of redshift, and the spectrum of the diffuse radiation field is computed. It is shown that J912 increases by a factor of 25-35 between the present epoch and z about 2. The attenuation of 912 A due to the accumulated absorption is a factor of 4 = 6 over the z = 2-4 redshift range: at this epoch, the background flux is found to decrease slowly from a peak value of J912 about 1-2 x 10 exp -22 ergs/sq cm/s/Hz/sr. The estimated ionizing flux is consistent with 2 sigma upper limits to the Gunn-Peterson optical depth at high redshifts only for Omega(IGM) h(50) exp 3/2 less than about 0.03. Also, the UV radiation from the observed QSOs falls slightly short of the amount needed to satisfy the 'proximity effects'. The redshift evolution of absorption system is discussed in terms of such a QSO-dominated background.
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