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A. Constantin, J. C. Shields (Ohio University)
Quasars show some diversity in the slopes of their optical/ultraviolet continuum, and an important question is the extent to which this variation stems from properties intrinsic to the accretion source, or alternatively to intervening dust in the circumnuclear environment. Several previous studies have produced evidence that more luminous quasars have bluer spectra, and the origin of this trend remains a matter of debate. In this presentation we will discuss the results of simulations designed to study the possible role of circumnuclear dust in producing the observed luminosity dependence. Monte Carlo methods are employed in a scheme in which the inner radius of the absorbing material scales with the intrinsic luminosity of the central source (a variant of the ``receding torus'' picture), consistent with expectations that grains will evaporate above a certain radiation density. We show that this simple model results in a statistical dependence of reddening in general accord with the observed correlation between quasar luminosity and continuum slope. The gas associated with the dust would also be expected to absorb x-rays, and the resulting numbers of absorbed sources predicted by this model appear consistent with recent x-ray observations of the extragalactic point source population.
The author(s) of this abstract have provided an email address for comments about the abstract: constant@helios.phy.ohiou.edu
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.