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2003MNRAS.340..473S - Mon. Not. R. Astron. Soc., 340, 473-484 (2003/April-1)
The nature of the ionizing background at z ~ 2.5-5.
SOKASIAN A., ABEL T. and HERNQUIST L.
Abstract (from CDS):
In order to simultaneously match observational estimates of the HI and HeII opacities, we find that galaxies and quasars must contribute approximately equally to the ionizing background in HI at z ≃ 3. Moreover, our analysis requires the stellar component to rise for z > 3 to compensate for the declining contribution from bright quasars at higher redshift. This inference is consistent with some observational and theoretical estimates of the evolution of the cosmic star formation rate. The increasing dominance of the stellar component towards high redshift leads to a progressive softening of the UV background, as suggested by observations of metal line absorption. In the absence of additional sources of ionizing radiation, such as mini-quasars or weak active galactic nuclei, our results, extrapolated to z > 5, suggest that hydrogen reionization at z ∼ 6 mostly probably occurred through the action of stellar radiation.
Abstract Copyright: 2003 RAS
Journal keyword(s): radiative transfer - intergalactic medium - quasars: general - diffuse radiation
Simbad objects: 3
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