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Astron. Astrophys. 321, 379-388 (1997)


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Velocity dispersions and mass-to-light ratios for 9 globular clusters in M 31

P. Dubath 1, 2 and Carl J. Grillmair 3

1 Observatoire de Genève, ch. des Maillettes 51, CH-1290 Sauverny, Switzerland
2 INTEGRAL Science Data Centre, ch. d'Écogia 16, CH-1290 Versoix, Switzerland
3 Jet Propulsion Laboratory, 4800 Oak Grove Drive, Mail Stop 179-225, Pasadena, CA 91109, USA

Received 5 September 1996 / Accepted 21 October 1996

Abstract

We present internal velocity dispersion determinations from high-resolution spectroscopic observations of a sample of nine globular clusters in M 31. Comprehensive numerical simulations are used to show that the typical uncertainty of our velocity dispersion measurements is [FORMULA] 5%. Using these new velocity dispersions together with structural parameters derived from HST observations, we estimate the [FORMULA] ratios of these clusters and find that they are typical of those measured for Galactic clusters. We show relations between velocity dispersion, luminosity and physical scales for globular clusters belonging to the Galaxy, the Magellanic clouds, Fornax, M 31, and Centaurus A. The mean relations and the degree of scatter are similar in all galaxies. This reveals remarkable similarities, in term of structure and [FORMULA] ratio, between the globular clusters belonging to these different galaxies. We briefly discuss the possible use of individual globular clusters as extragalactic distance indicators.

Key words: galaxies: individual: M 31 – galaxies: star clusters – galaxies: halos – stars: kinematics – techniques: radial velocities

Send offprint requests to: Pierre.Dubath@obs.unige.ch

© European Southern Observatory (ESO) 1997

Online publication: June 30, 1998

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