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For refcode 1995AJ....109.1485O:
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1995AJ....109.1485O ON THE ELLIPTICITY OF THE SHAKHBAZIAN COMPACT GROUPS OF GALAXIES H. OLEAK, D. STOLL, AND H. TIERSCH University of Potsdam, c/o Astrophysikalisches Institut Potsdam, An der Stemwarte 16, D-14482 Potsdam, Germany Electronic mail: holeak@aip.de H. T. MACGILLIVRAY Royal Observatory, Blackford Kill, Edinburgh, EH9 310, Scotland, United Kingdom Electronic mail: hmg@cosmos.roe.ac.uk Received 1994 September 12; revised 1994 November 29 ABSTRACT We have determined the ellipticities of compact groups of galaxies in the Shakhbazian survey, using the technique proposed by Rood (ApJ, 233,21(1979)] for deriving the average flatness of a large sample of objects. Our sample contains 95 Shakhbazian groups with accurate parameters obtained from the COSMOS/UKSTU catalogue of the Southern sky. We find a broad distribution for the apparent axial ratios (q = b/a) of the groups with a mean of <b/a> = 0.5. This observation distribution is compared with randomly generated spherical and elliptical systems. We argue that the frequency distribution of axial ratios for Shakhbazian groups is represented solely by a population of prolate spheroids with low intrinsic axial ratios, <q> = 0.3, {sigma} = +/-0.15 (assuming random true orientations in 3D space). The Shakhbazian groups are more highly flattened than either rich clusters or elliptical galaxies, and represent the most elongated systems yet found. We discuss this finding in the light of other observations of Shakhbazian groups, and suggest further analyses which may help towards understanding the true nature of these systems.
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