THE SHAPES OF SHAKHBAZIAN COMPACT-GROUPS OF GALAXIES

We have completed an investigation (preliminary results for which were reported in Oleak et al. 1995) into the shapes of Shakhbazian compact groups of galaxies. Ellipticities for 299 groups in the Shakhbazian s urvey have been examined using the technique proposed by Rood (1979) f or deriving the average ''flatness'' of a large sample of objects. The distribution of the apparent axial ratios (g = b/a) for the groups is found to be broad with mean of [b/a] similar to 0.5. This distributio n is compared with randomly generated spherical and elliptical model s ystems. The results confirm the findings of our earlier study: the fre quency distribution of axial ratios for Shakhbazian groups is represen ted solely by a population of prolate spheroids with low intrinsic axi al ratios, [q] = 0.3, sigma = +/-0.17 (assuming random true orientatio ns in 3D space). This now provides further strong evidence that the Sh akhbazian groups are more highly flattened than either rich clusters o r elliptical galaxies, and represent the most elongated systems yet fo und. The result also provides confirmation of the reality of the group s, since in the case of systems of chance line-of-sight superpositions of galaxies we would expect to see much higher axial ratios.