Obscuration of Quasars by Dust and the Reddening Mech in by F. Masci

By F. Masci

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The existence of a smooth IGM dust component also remains a major uncertainty. Due to their deep gravitational potential, Margolis & Schramm (1977) showed that it is unlikely for supernovae-driven winds to expel significant quantities of dust from a massive galaxy to large scales. For low mass galaxies however (eg. dwarfs), Babul & Rees (1992) show that this mechanism can be effective. Such systems are believed to comprise a majority of the ‘faint42 blue population’ which show an excess ∼ 20 − 30 times that predicted from non-evolving galaxy models for B > 24 (eg.

The numbers of background sources behind clusters is also expected to be modified by gravitational lensing (GL) by the cluster potential. Depending on the intrinsic luminosity function of the background population, and the limiting magnitude to which the sources are detected, GL can cause either an enhancement or a deficit in the number of background sources. The GL effect has been used to explain various reports of overdensities of both optically and radio-selected quasars behind foreground clusters (Bartelmann & Schneider, 1993; Bartelmann et al.

A dust density distribution with n = 3/2 (Eqn. 9) 37 appears to best satisfy the ‘small scale’ cluster-QSO angular correlation study of Boyle et al. (1988). 4 Diffuse Intergalactic Dust? There have been a number of studies claiming that the bulk of metals in the local universe had already formed by z ∼ 1 (eg. Lilly & Cowie, 1987; White & Frenk, 1991; Fall & Pei, 1995). Similarly, models of dust evolution in the galaxy show that the bulk of its dust content was formed in the first few billion years (Wang, 1991).

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