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Astron. Astrophys. 325, 144-148

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A simple effective method to estimate the galactic extinction towards galaxies in the plane of the Milky Way

M. Gajdosík1,2 and R. Weinberger1

1Institut für Astronomie der Leopold-Franzens-Universität Innsbruck, Technikerstraße 25, A-6020 Innsbruck, Austria (http://astro.uibk.ac.at)
2Department of Astronomy and Astrophysics, Faculty for Mathematics and Physics, Comenius University, Mlynská Dolina, 842 15 Bratislava, Slovak Republic (gajdosik@center.fmph.uniba.sk)

Received 22 August 1996 / Accepted 23 January 1997


Elliptical galaxies and bulges of spiral galaxies have quite similar, well-defined optical colours. It is just these bulges that are left if a (spiral) galaxy suffers from a considerable foreground extinction as is the case for many of the thousands of galaxies that have been detected in recent years in the "zone-of-avoidance" of the Milky Way. By use of the "old" Palomar Sky Survey (whose red-sensitive and blue-sensitive exposures had consecutively been taken for each field), measuring the red and blue bulge profiles there, led to astonishingly accurate results for their galactic, i.e. foreground extinction. With this quick and simple method it will be possible in future to determine the total galactic extinction along many lines-of-sight in the Galaxy, to supplement data on the spatial distribution of the interstellar extinction with a maximum value and, eventually, to develop a dust-model of the Milky Way. We detected a pronounced dependence of the 100 µm vs FORMULA or 60µm vs FORMULA ratio on the galactic longitude.

Key words: methods: observational - (ISM:) dust, extinction - Galaxy: structure - galaxies: fundamental parameters

Send offprint requests to: M. Gajdosík

© European Southern Observatory (ESO) 1997