The Formation of Compact Groups of Galaxies. II. X-Ray Properties. Diaferio, A. The Astronomical Journal, 109(3):868-879, 6, 1995.
The Formation of Compact Groups of Galaxies. II. X-Ray Properties [pdf]Paper  The Formation of Compact Groups of Galaxies. II. X-Ray Properties [link]Website  abstract   bibtex   
We use N-body/hydrodynamic simulations of collapsing rich galaxy groups to predict X-ray properties of compact groups. The model is consistent with the X-ray observations of a few compact groups and naturally explains the correlation between the spiral fraction and the velocity dispersion and crossing time observed in compact groups. The model predicts a correlation between X-ray luminosity and gas temperature only if the systems are bound. The model is an extension of the one used by Diaferio et at. [AJ, 107,868(1994)] to show that substructures within collapsing rich loose groups have dynamical properties and a multiplicity function similar to the Hickson compact groups. So far, both X-ray and optical results suggest that most observed compact groups are three- dimensional systems rather than chance alignments of unrelated galaxies. We propose some direct observational tests to discriminate among models.

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