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The formation of compact groups of galaxies. I: Optical propertiesThe small crossing time of compact groups of galaxies (t(sub cr)H(sub 0) approximately less than 0.02) makes it hard to understand why they are observable at all. Our dissipationless N-body simulations show that within a single rich collapsing group compact groups of galaxies continually form. The mean lifetime of a particular compact configuration if approximately 1 Gyr. On this time scale, members may merge and/or other galaxies in the loose group may join the compact configuration. In other words, compact configurations are continually replaced by new systems. The frequency of this process explains the observability of compact groups. Our model produces compact configurations (compact groups (CG's) with optical properties remarkably similar to Hickson's (1982) compact groups (HCG's): (1) CG's have a frequency distribution of members similar to that of HCG's; (2) CG's are approximately equals 10 times as dense as loose groups; (3) CG's have dynamical properties remarkably similar to those of HCG's; (4) most of the galaxy members of CG's are not merger remnants. The crucial aspect of the model is the relationship between CG's and the surrounding rich loose group. Our model predicts the frequency of occurrence of CG's. A preliminary analysis of 18 rich loose groups is consistent with the model prediction. We suggest further observational tests of the model.
Document ID
19950036247
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Diaferio, Antonaldo
(Milan Univ. Milan, Italy)
Geller, Margaret J.
(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA United States)
Ramella, Massimo
(Osservatorio Astronomico di Trieste Trieste, Italy)
Date Acquired
August 16, 2013
Publication Date
March 1, 1994
Publication Information
Publication: Astronomical Journal
Volume: 107
Issue: 3
ISSN: 0004-6256
Subject Category
Astrophysics
Accession Number
95A67846
Funding Number(s)
CONTRACT_GRANT: NASW-201
Distribution Limits
Public
Copyright
Other

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