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The stellar kinematics of the giant halos of Brightest Cluster Galaxies

Published online by Cambridge University Press:  06 October 2004

George K. T. Hau
Affiliation:
European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Germany email: [email protected] Current address: Department of Physics, Durham University, South Road, Durham DH1 3LE, UK
M. Hilker
Affiliation:
Sternwarte der Universität Bonn, Auf dem Hügel 71, D-53121, Bonn, Germany
T. Bridges
Affiliation:
Department of Physics, Queen's University, Kingston, Ontario, K7L 3N6, Canada
D. Carter
Affiliation:
Astrophysics Research Institute, Liverpool John Moores University, L41 1LD, UK
H. Dejonghe
Affiliation:
Department of Mathematical Physics and Astronomy, Ghent University, B-9000 Belgium
S. De Rijcke
Affiliation:
Department of Mathematical Physics and Astronomy, Ghent University, B-9000 Belgium
H. Quintana
Affiliation:
Facultad de Física y Astronomía, Universidad Católica de Chile, Santiago, Chile
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Abstract

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We have investigated the stellar kinematics of two brightest cluster galaxies (BCGs) to large distances from the cluster centre. In both galaxies, the velocity dispersion rises with radius. Orbital anisotropy is ruled out as the cause and we conclude that the kinematics in the outer parts of BCGs are dark matter dominated. This result contrasts with the current problem for intermediate luminosity ellipticals, which appear to have less dark matter than predicted by CDM. Combining the present results with our previous work, the fraction of BCGs with outwardly rising dispersions ($\sim60\%$) is much higher than that found previously ($\sim7\%$) from the inner parts of BCGs. We argue that this phenomenon may be more common than previously thought. The agreement with radial trends expected for a smooth galaxy/cluster transition, and the lack of dependence on cD/BCG dominance and cluster environment, suggest that the outwardly rising dispersion is a genuine response of the stars to the underlying cluster potential. There is evidence that BCG in Abell 2063 is not at the centre of the cluster potential.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Type
Contributed Papers
Copyright
© 2004 International Astronomical Union