Quasars in the Cosmic Environment

Abstract

We now consider the environment of quasars in the widest possible sense, from the circumnuclear regions to very large scales of hundreds ofkiloparsecs. The circumgalactic environment of nearby quasars has beenwidely studied since the late 1960s in an attempt to test its influenceon the triggering of nuclear activity. The underlying hypothesis is thatgravitational perturbations might ease the infall of matter toward thenucleus, providing accretion material for the central black hole.