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Paper: The evolution of quasars in galaxy cluster environments
Volume: 10, Evolution of the Universe of Galaxies: Edwin Hubble Centennial Symposium
Page: 334
Authors: Ellingson, E.
Abstract: In previous studies of bright, radio-loud quasars, it has been found (Yee and Green, 1987) that these objects at redshifts greater than about 0.6 are often found situated in galaxy-cluster environments as rich as Abell-richness class 1 or greater but not at lower redshifts. At low redshifts, however, optically bright radio-loud quasars are only found in poorer environments. This result may be evidence that quasars in these environments have faded since that epoch. Imaging of the environments of an optically faint sample of radio-loud quasars at redshifts between 0.3 and 0.6 has identified several faint quasars in rich galaxy clusters, suggesting a statistical-fading timescale of 900 million years. This result indicates that the population of radio-loud quasars in rich environments evolve much more rapidly than those in poor environments and that environment plays a crucial role in the triggering and sustenance of quasar activity. Radio-quiet quasars are not found in these rich environments, and there is a difference in the underlying physical properties of these two types of objects.
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