7 research outputs found
Analytic Model for Advection-Dominated Accretion Flows in a Global Magnetic Field
A model for advection-dominated accretion flows (ADAFs) in a global magnetic
field is proposed. In contrast to the well known ADAF models in which the
viscosity of a fluid determines both angular momentum transfer and energy
dissipation in the flow, the magnetic field and the electric resistivity,
respectively, control them in this model. A manageable set of analytic
solutions for the flow and the magnetic field is obtained to vertically
non-integrated basic equations. This set describes mathematically a fully
advective accretion flow and, in physically plausible situations for most AGNs,
it is also confirmed that the radiation cooling estimated on this solution is
really negligible compared with the internal energy of the flow.Comment: 27pages, 1 figure, to appear in ApJ vol 529, Feb.1, 200
In the Beginning: The First Sources of Light and the Reionization of the Universe
The formation of the first stars and quasars marks the transformation of the
universe from its smooth initial state to its clumpy current state. In popular
cosmological models, the first sources of light began to form at redshift 30
and reionized most of the hydrogen in the universe by redshift 7. Current
observations are at the threshold of probing the hydrogen reionization epoch.
The study of high-redshift sources is likely to attract major attention in
observational and theoretical cosmology over the next decade.Comment: Final revision: 136 pages, including 42 figures; to be published in
Physics Reports 2001. References updated, and a few minor corrections made.
In this submission, several figures were compressed, resulting in just a
slight reduction in quality; a postscript file with the full figures is
available at http://www.cita.utoronto.ca/~barkana/review.htm