From regular motion to chaos in galaxy models with massive nuclei
           N.D. Caranicolas
     Department of physics, section of astrophysics,
     astronomy and mechanics, university of Thessaloniki,
           540 06 Thessaloniki, Greece
                   and
          K.A. Innanen
      Department of physics,York university,
      4700 KEELE Street, North York, Ontario M3J 1P3 Canada


Abstract, Simple galactic models, with relatively massive spherical
nuclei, are used for the study of orbits of low angular momentum
stars in the meridian plane of an axially-symetric galaxy. Our
theoretical analysis shows how, when stars move in resonant orbits, the
resonance depends on the particular values of the model parameters,
that is, on the particular structure of the galaxy. A semi-numerical
method is proposed to describe the "global" resonant behavior of a disk
and nucleus systems, for low angular momentum stars. The theoretical
results are verified by numerical integration of the equations of
motion. Stars moving near the galactic plane are scattered to higher Z
and show chaotic motion only when the system is near the 1/1 resonance.
Orbits are regular when the ratio of the frequencies is far from the
1/1 resonance.

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