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Astron. Astrophys. 329, 920-936 (1998)


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The distribution of nearby stars in phase space
mapped by Hipparcos *

I. The potential well and local dynamical mass

M. Crézé 1, 2, E. Chereul 1, O. Bienaymé 1 and C.Pichon 3

1 Centre de Données astronomique de Strasbourg, CNRS URA1280 11 rue de l'Université, F-67000 Strasbourg, France
2 IUP de Vannes, 8 rue Montaigne, BP 561, F-56017 Vannes Cedex, France
3 Astronomisches Institut Universität Basel, Venusstrasse 7, CH-4102 Binningen, Switzerland

Received 6 May 1997 / Accepted 29 July 1997

Abstract

Hipparcos data provide the first, volume limited and absolute magnitude limited homogeneous tracer of stellar density and velocity distributions in the solar neighbourhood. The density of A-type stars more luminous than [FORMULA] can be accurately mapped within a sphere of 125 pc radius, while proper motions in galactic latitude provide the vertical velocity distribution near the galactic plane. The potential well across the galactic plane is traced practically hypothesis-free and model-free. The local dynamical density comes out as [FORMULA] a value well below all previous determinations leaving no room for any disk shaped component of dark matter.

Key words: Galaxy: kinematics and dynamics – Galaxy: fundamental parameters – Galaxy: halo – solar neighbourhood – Galaxy: structure – dark matter

* Based on data from the Hipparcos astrometry satellite

Send offprint requests to: M. Crézé

© European Southern Observatory (ESO) 1998

Online publication: December 16, 1997
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