EDP Sciences
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Volume 412, Number 2, December III 2003
Page(s) 387 - 398
Section Galactic structure and dynamics
DOI http://dx.doi.org/10.1051/0004-6361:20031467

A&A 412, 387-398 (2003)
DOI: 10.1051/0004-6361:20031467

Simulations of dual morphology in spiral galaxies

S. L. Berman

Theoretical Physics, University of Oxford, 1 Keble Road, Oxford, UK
(Received 17 February 2003 / Accepted 15 September 2003 )

Gas and stars in spiral galaxies are modelled with a combination of hydrodynamic and N-body techniques. The simulations reveal morphological differences mirroring the dual morphologies seen in  B and  K' band observations of many spiral galaxies: gaseous images have tighter pitch angles, are more asymmetric, more flocculent and more likely to have multiple arms. Morphological decoupling increases as the stellar arm-interarm contrast and the  Q parameter fall. The flocculence of a galaxy is quantified by decomposing the images into logarithmic spirals and defining a parameter closely related to the uniformity of the resulting 2D Fourier spectrum. Thus, a significant amount of morphological decoupling in spiral galaxies is shown to be due to the difference in the dynamics of stars and gas, rather than dust, star formation or galaxy interactions.

Key words: hydrodynamics -- galaxies: ISM -- galaxies: structure -- galaxies: spiral -- galaxies: fundamental parameters -- infrared: galaxies

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