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No relation between the vertical velocity component and the absolute magnitude among globular clusters

Published online by Cambridge University Press:  18 January 2010

E. A. De Souza–Rossetto  and
H. J. Rocha–Pinto
E. A. De Souza–Rossetto
Affiliation:
Observatório do Valongo, Universidade Federal do Rio de Janeiro, Ladeira Pedro Antônio, 43, Saúde, Rio de Janeiro, Brazil email: erika@astro.ufrj.br, helio@astro.ufrj.br
H. J. Rocha–Pinto
Affiliation:
Observatório do Valongo, Universidade Federal do Rio de Janeiro, Ladeira Pedro Antônio, 43, Saúde, Rio de Janeiro, Brazil email: erika@astro.ufrj.br, helio@astro.ufrj.br
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Abstract

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The globular cluster luminosity function distribution shows a peak at MV ≈ −7.5 mag. There are some indications that the kinematic parameters are correlated with luminosity. In particular, Alfaro et al. (2001) have studied the properties of the Galactic globular cluster system and they found a correlation between spatial-velocity component and globular cluster absolute magnitude. The authors assumed that the globular clusters can be separated into two groups. The first is composed of globular clusters with MV < −7.5 mag and moving preferentially towards the north Galactic pole, while the faintest globular clusters, composing the second group, move towards the Galactic disk. We have selected a sample of globular clusters using the same criteria as Alfaro et al. (2001) and have checked that this apparent relation indeed exists. Nevertheless, we decided to investigate whether it could be a fortuitous relation or an intrinsic property by checking its validity for eight different epochs at past and future times. The orbital parameters for the globular clusters at these eight epochs were found by orbital integration using a typical Galactic potential. We show that this relation between the vertical velocity component and the absolute magnitude among globular clusters is not coherent with time and the velocity distribution does not support the hypothesis of Alfaro et al. for the existence of two dynamical groups of globular clusters.

Keywords

globular clusters: general
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 5 , Symposium S266: Star clusters: basic galactic building blocks throughout time and space , August 2009 , pp. 380 - 383
Copyright
Copyright © International Astronomical Union 2010

References

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