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COSMOLOGICAL ORIGIN OF QUASARS

Quasars are the earliest objects known to exist. We examine their origin in the context of popular models for structure formation in the universe. We show that seeds for quasar black holes could have originated from the initial cosmological collapse of overdense regions with unusually small rotation. Most of these seeds have a mass of order 10^6 solar masses, just above the cosmological Jeans mass. For Cold Dark Matter cosmologies, we find of order one seed black hole per bright galaxy. After the galaxy forms, the seeds inside its bulge sink to the center by dynamical friction. We also describe a few empirical methods to study the properties of quasars and their environments. These include: probing quasar hosts through [C II] emission, finding quasar lifetimes from the ``proximity effect'' along two lines of sight, and measuring the amplitude of clustering at high redshifts through the detection of Lyman-alpha clouds beyond the quasar redshift.