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Astron. Astrophys. 353, 117-123 (2000)

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Is the exponential distribution a good approximation of dusty galactic disks?

A. Misiriotis 1,2,4, N.D. Kylafis 1,2, J. Papamastorakis 1,2 and E.M. Xilouris 2,3

1 University of Crete, Physics Department, P.O. Box 2208, 710 03 Heraklion, Crete, Greece
2 Foundation for Research and Technology-Hellas, P.O. Box 1527, 711 10 Heraklion, Crete, Greece
3 University of Athens, Department of Physics, Section of Astrophysics, Astronomy and Mechanics, 157 83 Athens, Greece
4 Observatoire de Marseille, 2 Place Le Verrier, 13248 Marseille Cedex 4, France

Received 6 August 1999 / Accepted 27 October 1999


We investigate how significant the spiral structure is on calculations concerning radiative transfer in dusty spiral galaxies seen edge-on. The widely adopted exponential disk model (i.e. both the stars and the dust are distributed exponentially in the radial direction and also perpendicular to the plane of the disk) is now subject to a detailed comparison with a realistic model that includes spiral structure for the stars and the dust in the disk. In particular, model images of galaxies with logarithmic spiral arms are constructed, such that the azimuthally averaged disk is exponential in radius and in height, as the observations suggest. Then, pure exponential disk models (i.e. with no spiral structure) are used to fit the edge-on appearance of the model images. As a result, the parameters derived after the fit are compared to the real values used to create the spiral-structured images. It turns out that the plain exponential disk model is able to give a very good description of the galactic disk with its parameters varying only by a few percent from their true values.

Key words: ISM: dust, extinction – galaxies: photometry – galaxies: spiral – galaxies: structure

Send offprint requests to: A. Misiriotis (angmis@physics.uch.gr)

© European Southern Observatory (ESO) 2000

Online publication: December 8, 1999