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Astron. Astrophys. 352, 459-468 (1999)

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Constraining galactic structure parameters from a new extinction model and four star count samples

B. Chen 1,2, F. Figueras 1,3, J. Torra 1,3, C. Jordi 1,3, X. Luri 1,3 and D. Galadí-Enríquez 1

1 Departament d'Astronomia i Meteorologia, Universitat de Barcelona, Avda. Diagonal 647, 08028 Barcelona, Spain
2 Center for Astrophysical Sciences, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA
3 Institut d'Estudis Espacials de Catalunya, Edif. Nexus, Avda. Gran Capità 2-4, 08034 Barcelona, Spain

Received 22 December 1998 / Accepted 1 November 1999


We propose a new 3-dimensional extinction model based on the COBE/IRAS all sky reddening map. Its application to globular and open cluster data evidences that the COBE/IRAS reddening map has an accuracy of 18%, but overestimates visual absorption by a factor of 1.16. This systematic error does not change with galactic latitude and opacity significantly.

The implementation of the new extinction model has optimized our galactic structure and kinematic model to low-galactic latitudes. Four star count samples distributed in different galactic directions have been compared with galactic model simulations. Numerical experiments allow us to constrain the radial distribution of the galactic disk. The disk scale length is found to be 2250 [FORMULA] 50 pc and the displacement of the Sun from the galactic plane [FORMULA] = 27.5 [FORMULA] 6.0 pc.

Key words: ISM: dust, extinction – Galaxy: globular clusters: general – Galaxy: open clusters and associations: general – methods: statistical – astronomical data bases: miscellaneous – Galaxy: solar neighbourhood

Send offprint requests to: B. Chen (bchen@pha.jhu.edu)

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© European Southern Observatory (ESO) 1999

Online publication: December 2, 1999