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Astron. Astrophys. 354, 761-766 (2000)

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Quantifying substructure in galaxy clusters

Alexander Knebe 1,2 and Volker Müller 1

1 Astrophysikalisches Institut Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
2 Theoretical Physics, 1 Keble Road, Oxford OX1 3NP, UK

Received 25 January 1999 / Accepted 21 December 1999

Abstract

Substructure in galaxy clusters can be quantified with the robust [FORMULA] statistics (Dressler and Shectman 1988) which uses velocity kinematics and sky projected positions. We test its sensitivity using dissipationless numerical simulations of cluster formation. As in recent observations, about 30% of the simulated clusters show substructure, but the exact percentage depends on the chosen limit for defining substructure, and a better discriminator is the distribution function of the [FORMULA] statistics. The Dressler-Shectman statistics correlate well with other subcluster indicators, but with large scatter due to its sensitivity to small infalling groups and projection effects.

Key words: galaxies: clusters: general – cosmology: observations – cosmology: theory

Send offprint requests to: A. Knebe

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© European Southern Observatory (ESO) 2000

Online publication: February 25, 2000
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