EDP Sciences
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Volume 372, Number 1, June II 2001
Page(s) 95 - 104
Section Stellar clusters and associations
DOI http://dx.doi.org/10.1051/0004-6361:20010380

A&A 372, 95-104 (2001)
DOI: 10.1051/0004-6361:20010380

The association surrounding NGC 2439

N. Kaltcheva1, 2, R. Gredel3 and C. Fabricius2

1  Department of Astronomy, University of Sofia, 5 James Bourchier Avenue, 1164 Sofia, Bulgaria
2  Niels Bohr Institute for Astronomy, Physics and Geophysics, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark
    e-mail: cf@astro.ku.dk
3  Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
    e-mail: gredel@mpia-hd.mpg.de

(Received 9 October 2000 / Accepted 6 March 2001 )

The structure of the field surrounding the Galactic cluster NGC 2439 is studied utilizing $uvby\beta$ photometry of bright OB stars. We collate all photometric and kinematic data available to identify possible groupings. The stars of our sample show a large scatter in their distances, radial velocities, proper motions and reddenings. We conclude that they do not belong to a single stellar association. We find evidence of the existence of three coherent structures at distances of 370 pc, 1 kpc, and 2.6-3.2 kpc. The high stellar density toward NGC 2439 is very likely due to a decreased absorption in this direction, which poses some doubt on the reality of the cluster. A comprehensive $uvby\beta$ study of NGC 2439 is required to clarify its nature. The spatial distribution of the stars and their reddening are used to characterise the spatial distribution of the visual extinction in the region. The results obtained confirm previously determined constraints on the formation mechanism of interstellar CH+ towards the NGC 2439 field.

Key words: stars: early type -- stars: fundamental parameters -- open clusters and associations: individual: NGC 2439 -- ISM: clouds

Offprint request: Kaltcheva, nadia@phys.uni-sofia.bg

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