Astron. Astrophys. 349, 369-380 (1999)

Multi-component models for disk galaxies

I. Stellar rotation and anisotropy

Ezio Pignatelli and Giuseppe Galletta

Dipartimento di Astronomia, Università di Padova, Vicolo dell' Osservatorio, 5, I-35122 Padova, Italy

Received 9 May 1997 / Accepted 24 June 1999

Abstract

We present here a self-consistent, tridimensional model of a disc galaxy composed by a number of ellipsoidal distributions of matter having different flattening and density profile. The model is self-consistent and takes into account the observed luminosity distribution, the flattening profile and the stellar rotation- and velocity dispersion- curves. In this paper we considered the particular case of a disc galaxy composed by two spheroidal bodies: an exponential disc and a bulge following the law.

We studied the behavior of the stellar rotation- and velocity dispersion- profiles along the sequence of S0s and Spirals, identified by an increasing disc-to-bulge ratio. Inside every class, kinematic curves were produced by changing the relative concentration of the two components and the inclination of the galaxy with respect to the line of sight. The comparison with observational data requires only two scaling factors: the total mass of the galaxy, and the effective radius.

The model allows also to detect the presence of anisotropy in the velocity distribution. In the special case of S0s, we explored the sensitivity of the kinematics of the model by changing the anisotropy and the flattening of the bulge. For intermediate flattening () it is possible to distinguish a change of anisotropy of 15%

To show a real case, the model has been applied to the photometric and kinematic data of NGC 5866. We plan to apply these models to a larger database of S0 galaxies in a future paper.

Key words: galaxies: fundamental parameters galaxies: general galaxies: individual: NGC 5866 galaxies: kinematics and dynamics galaxies: structure

Send offprint requests to: G. Galletta

SIMBAD Objects

Contents

• 1. Introduction
• 2. The hypothesis of the model
  • 2.1. The density profiles
  • 2.2. The velocity distribution
• 3. The equations
• 4. The parameters
• 5. The results
  • 5.1. The models and the Hubble diagram
  • 5.2. The anisotropy in bulges
    • 5.2.1. Anisotropy and stability
    • 5.2.2. Inferring the anisotropy from observations
• 6. A test case: NGC 5866
• 7. Conclusions
• Acknowledgements
• Appendix A: Gauss-Hermite expansion of the line shape
• References

© European Southern Observatory (ESO) 1999

Online publication: September 2, 1999
helpdesk.link@springer.de