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Astron. Astrophys. 336, 137-149 (1998)


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Comparison of two different extinction laws with Hipparcos observations *

B. Chen 1, J.L. Vergely 2, B. Valette 3 and G. Carraro 4, 5

1 Departament d'Astronomia i Meteorologia, Universitat de Barcelona, Avda. Diagonal 647, E-08028 Barcelona, Spain
2 Observatoire de Strasbourg, 11, rue de l'Université, F-67000 Strasbourg, France
3 Institut de Physique du Globe de Paris, F-75007 Paris, France
4 Department of Astronomy, Padova University, Vicolo dell'Osservatorio 5, I-35122 Padova, Italy
5 SISSA/ISAS, via Beirut 2, I-34013 Trieste, Italy

Received 5 January 1998 / Accepted 28 April 1998

Abstract

Interstellar absorption in the galactic plane is highly variable from one direction to another. In this paper colour excesses and distances from a new open cluster sample are used to investigate the spatial distribution of the interstellar extinction. An inverse method (Tarantola & Valette, 1982) is used to construct the extinction map in the galactic plane below [FORMULA]. The [FORMULA] diagrams are compared with those derived from individual stars (Arenou et al. 1992, Neckel & Klare 1980). An analytic expression for the interstellar extinction as a function of galactic longitude and distance in the solar neighborhood is given. The comparison of the model predictions with Hipparcos observations in the 4-dimensional space of (V, [FORMULA], [FORMULA], r) shows that our extinction model provides a better fit to the data. However, a new and more detailed extinction model is still lacking.

Key words: methods: statistical – ISM: dust, extinction – Galaxy: open clusters and associations: general – Galaxy: solar neighbourhood

* Based in part on observations made with the ESA Hipparcos astrometry satellite

Send offprint requests to: bchen@mizar.am.ub.es

© European Southern Observatory (ESO) 1998

Online publication: July 7, 1998

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