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Astron. Astrophys. 343, 733-739 (1999)

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Substructure in the ENACS clusters

José M. Solanes 1, Eduard Salvador-Solé 2 and Guillermo González-Casado 3

1 Departament d'Enginyeria Informàtica, Universitat Rovira i Virgili, Carretera de Salou, s/n; E-43006 Tarragona, Spain (jsolanes@etse.urv.es)
2 Departament d'Astronomia i Meteorologia, Universitat de Barcelona, Av. Diagonal 647, E-08028 Barcelona, Spain (eduard@faess0.am.ub.es)
3 Departament de Matemàtica Aplicada II, Universitat Politècnica de Catalunya, Pau Gargallo 5, E-08028 Barcelona, Spain (guille@coma.upc.es)

Received 4 November 1998 / Accepted 3 December 1998

Abstract

Subclustering is investigated in a set of 67 rich cluster galaxy samples extracted from the ESO Nearby Abell Cluster Survey (ENACS) catalog. We apply four well-known statistical techniques to evaluate the frequency with which substructure occurs. These diagnostics are sensitive to different aspects of the spatial and velocity distribution of galaxies and explore different scales, thus providing complementary tests of subclustering. The skewness and kurtosis of the global radial velocity distributions, useful for judging the normality, and the powerful [FORMULA] test of Dressler & Shectman, which measures local deviations from the global kinematics, show that the ENACS clusters exhibit a degree of clumpiness in reasonable agreement with that found in other less homogeneous and smaller cluster datasets. On the other hand, the average two-point correlation function of the projected galaxy distributions reveals that only [FORMULA] of the systems investigated show evidence for substructure at scale lengths smaller than 0.2 [FORMULA]. This is much less than in earlier studies based on the Dressler & Shectman's cluster sample. We find indications of a possible systematic deficiency of galaxies at small intergalactic separations in the ENACS clusters.

Key words: methods: data analysis – galaxies: clusters: general – cosmology: observations

Send offprint requests to: J.M. Solanes

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© European Southern Observatory (ESO) 1999

Online publication: March 1, 1999
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