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Virialization in N-body models of the expanding universe. I - Isolated pairs. II - All pairs
Evrard, A. E.; Yahil, A.
AA(New York, State University, Stony Brook), AB(Cambridge University, England)
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 296, Sept. 15, 1985, p. 299-318. (ApJ Homepage)
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NASA/STI Keywords:
Astronomical Models, Big Bang Cosmology, Galactic Clusters, Many Body Problem, Universe, Virial Theorem, Computational Astrophysics, Eccentric Orbits, Galactic Evolution, Kepler Laws, Mass Distribution, Orbital Elements
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The degree of virialization of isolated pairs of galaxies is investigated in the N-body simulations of Efstathiou and Eastwood (1981) for open and critical universes, utilizing the three-dimensional information available for both position and velocity. The models are described, including the equation of scaling the model to the real universe and the method of extracting pair samples. The classical virial theorem is reformulated in an expanding universe by explicitly subtracting out the underlying Hubble expansion. It is shown that nearly half of the point masses in the simulations double up to form isolated pairs whose dynamics is dominated by their own two-body force, and that more than three-quarters of these pairs are bound in very eccentric orbits. The investigation is then extended to include all pairs of galaxies, regardless of isolation. It is found that both the classical virial theorem and Peebles's (1976) 'cosmic virial theorem' provide reasonable mass estimates for nonisolated pairs.

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