Linda Sparke 

U. Wisconsin 

        Multiply Barred and Lopsided Galaxies

High-resolution optical and near-infrared images of the centers of
barred galaxies have revealed smaller, secondary bars within the main
bar.  A recent survey with the WIYN telescope shows that these are
quite common: we find them in about 30% of our barred S0 and Sa
systems.  The inner bar appears randomly oriented with respect to the
main outer bar, suggesting that the two rotate independently.  I will
discuss how one can search for regular orbits in such a
periodically-changing gravitational potential, and how stars
following stable orbits could support the inner bar.  An additional
complication of disk galaxies is that the outer parts are often lopsided.
I will present a dynamical model for lopsidedness, and show how it can
explain the asymmetric character of the gas velocity fields measured
in real systems.