IAU Symposium Abstract S186-055P

Stellar and Ionized Gas Kinematics in Sa Galaxies

E.M. Corsini1, A. Pizzella1, F. Bertola1, M. Persic$^{2,3}$,
and P. Salucci3
1 Dipartimento di Astronomia, Universit\`a di Padova, Italy < corsini,pizzella,bertola@astrpd.pd.astro.it >
2 Osservatorio Astronomico di Trieste, Italy,
3 SISSA, Trieste, Italy < persic,salucci@sissa.it >

In order to derive the mass distribution, and therefore the dark matter content of the Sa spirals, we measured major axis kinematics of the stars and of the ionized gas in a sample of 7 galaxies. We obtained the velocity curves and the velocity dispersion profiles for both the stellar and the gaseous components. We found that the velocity dispersion of the gas is as high as that of the stars on a large radial range in at least 3 objects. Therefore random motions have to be taken in account to explain dynamical support of the gas. Assuming the gas to be clumpy distributed in collisionless cloudlets, we applied the asymmetric drift correction to the gas kinematics in order to derive the circular velocity curve. The validity of such approach is confirmed by the good agreement between the circular velocity so far derived and that inferred from the stellar kinematics in most of the sample galaxies. The obtained circular velocity curves were used to perform a mass model decomposition in terms of a bulge, a disk and an halo for each of the Sa observed.