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Hipparcos : : Contribution à la Détermination de la Densité Locale de Matière dans le Disque Galactique

Abstract : Since the first dynamical determinations of the local volume mass density, performed in 1922 (Kapteyn) and in 1932 (Oort), many other studies have been carried out, most of them based on the analysis of the density and velocity distributions of tracer sample of stars. Up to now, the low accuracy of the apparent magnitude measurements, of the absolute magnitudes (i.e. of the distances) and of the velocities was a major drawback to these methods. This thesis work is dedicated to the determination of the local volume mass density from the new and more accurate Hipparcos satellite’s data (parallaxes, positions and proper motions). We have designed several maximum likehood methods in order to estimate the scale height of a tracer sample of stars together with the sun’s height. These methods take into account the limiting apparent magnitude of the tracer samples. We have tested these 3 methods using simulations (influence of the samples size and parameters, of the magnitude censorship …). Applying one of these methods of F stars observed by Hipparcos, we have found a scale height of 9 +- 4 PC. The local volume mass density of the galactic disk is 0.11 +- 0.01 msun /pc3.
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Hong-Anh Pham. Hipparcos : : Contribution à la Détermination de la Densité Locale de Matière dans le Disque Galactique. Astrophysique [astro-ph]. Observatoire de Paris, 1996. Français. ⟨tel-02095275⟩

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