| Dust Obscured Quasars (2007) | |||||||||||||
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| . We find that nearly all radio-loud, flat spectrum quasars are obscured by a magnitude or more of dust. The dust is probably located in the quasar or its host galaxy. If radio-quiet QSOs have comparable amounts of dust, 80% have been missed by all existing surveys. These missing QSOs may explain the X-ray background. 1. Introduction It has long been folk wisdom in the field of quasar research that quasars are blue. There has been some discussion of dust in quasars, but the consensus has been that its effects are subtle. We claim that the apparent lack of dust is a selection effect. Nearly all detailed work on quasars has concentrated on the optically brightest, which are the least dust obscured. If an unbiassed sample of quasars is studied, the effects of dust are dramatic. 2 PAUL J. FRANCIS ET AL. Figure 1. The distribution of B \Gamma K colours for a complete sub-sample of the Parkes flat-spectrum survey, and for an optically selected QSO survey, the Large Bright QSO Survey (... | |||||||||||||
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