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The extinction by dust in the outer parts of spiral galaxies

R. F. Peletier·E. A. Valentijn·A. F. M. Moorwood·W. Freudling·J. H. Knapen·J. E. Beckman
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Abstract

To investigate the distribution of dust in Sb and Sc galaxies we have analyzed near-infrared and optical surface photometry for an unbiased sample of 37 galaxies. Since light in the $K$-band is very little affected by extinction by dust, the $B-K$ colour is a good indicator of the amount of extinction, and using the colour-inclination relation we can statistically determine the extinction for an average Sb/Sc galaxy. We find in general a considerable amount of extinction in spiral galaxies in the central regions, all the way out to their effective radii. In the outer parts, at D$_{K,21}$, or at 3 times the typical exponential scale lengths of the stellar distribution , we find a maximum optical depth of 0.5 in $B$ for a face-on galaxy. If we impose the condition that the dust is distributed in the same way as the stars, this upper limit would go down to 0.1.

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R. F. Peletier, E. A. Valentijn, A. F. M. Moorwood, W. Freudling, J. H. Knapen, J. E. Beckman. 1995-06-20. The extinction by dust in the outer parts of spiral galaxies. https://arxiv.org/abs/astro-ph/9506108

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