Can rotation curves reveal the opacity of spiral galaxies?
University of Crete, Physics Department, PO Box 2208, 710 03 Heraklion, Crete, Greece e-mail: firstname.lastname@example.org
Accepted: 21 April 2005
The observed anti-correlation between the inclination and the slope of the innermost part of the rotation curve can be attributed to dust extinction. However, the implied central face-on opacity of for the most luminous galaxies is embarrassingly high compared with studies of edge-on galaxies, which yield central face-on opacities equal to at most in the optical band. I show that the controversy can be resolved by adopting a model that includes the velocity dispersion of the emitters. Through the use of such a model, I reproduce the correlation between galaxy inclination and the slope of its inner rotation curve without having to resort to excessively high optical depth.
Key words: dust, extinction / galaxies: kinematics and dynamics / galaxies: spiral
© ESO, 2005