Journal Article

The structure of spiral galaxies — II. Near-infrared properties of spiral arms

M. S. Seigar and P. A. James

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 299, issue 3, pages 685-698
Published in print September 1998 | ISSN: 0035-8711
Published online September 1998 | e-ISSN: 1365-2966 | DOI:
The structure of spiral galaxies — II. Near-infrared properties of spiral arms

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We have imaged a sample of 45 face-on spiral galaxies in the K band, to determine the morphology of the old stellar population, which dominates the mass in the disc. The K-band images of the spiral galaxies have been used to calculate different characteristics of the underlying density perturbation such as arm strengths, profiles and cross-sections, and spiral pitch angles. Contrary to expectations, no correlation was found between arm pitch angle and Hubble type, and combined with previous results this leads us to conclude that the morphology of the old stellar population bears little resemblance to the optical morphology used to classify galaxies.

The arm properties of our galaxies seem inconsistent with predictions from the simplest density wave theories, and some observations, such as variations in pitch angle within galaxies, seem hard to reconcile even with more complex modal theories. Bars have no detectable effect on arm strengths for the present sample.

We have also obtained B-band images of three of the galaxies. For these galaxies we have measured arm cross-sections and strengths, to investigate the effects of disc density perturbations on star formation in spiral discs. We find that B-band arms lead K-band arms and are narrower than K-band arms, apparently supporting predictions made by the large-scale shock scenario, although the effects of dust on B-band images may contribute towards these results.

Keywords: galaxies: fundamental parameters; galaxies: spiral; galaxies: structure; infrared: galaxies

Journal Article.  0 words. 

Subjects: Astronomy and Astrophysics

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