THE CONSTRUCTION OF BARRED GALAXY MODELS USING NONLINEAR EXTENSIONS OF LINEAR-MODES

We present a new method for the construction of quasi-self-consistent dynamical models for the stellar component of barred or spiral galaxie s, based on the nonlinear extension of linear modes. Just like N-body simulations, these barred models are guaranteed to be physical, since they are based on the presence of a global instability in an initially axisymmetric system. In addition, the full distribution function is o btained with very high accuracy and resolution, making this method par ticularly well suited for the interpretation of high quality observati onal data, such as line-of-sight velocity distributions (LOSVDs). We s how that such a model produces distribution functions, and hence LOSVD s, that are different from models based on purely linear modes. We cre ated a barred galaxy model using this method, and calculated observabl e kinematics: velocity fields, dispersion fields, vertex deviations an d LOSVDs. The behaviour of the stellar component turns out to be quali tatively very similar to the gaseous component, but the kinematic sign ature of the bar is not so well pronounced, as a result of the presenc e of velocity dispersion. However, we show that LOSVDs can show a very clear signature of the bar, and may even become double-peaked in some places. This indicates that the comparison of observed stellar line p rofiles with detailed models may provide important information, such a s bar masses and eccentricities, pattern speeds, etc.