Populating stellar orbits inside a rotating, gaseous bar

In an effort to understand better the formation and evolution of barred gal axies, we have examined the properties of equatorial orbits in the effectiv e potential of one specific model of a rapidly rotating, steady state gasdy namical bar that has been constructed via a self-consistent hydrodynamical simulation. At a given value of the Jacobi constant, roughly half of all te st particles (stars) that are injected into the equatorial plane of this po tential follow quasi-ergodic orbits; most regular prograde orbits have an o verall "bow tie" shape; and some trace out trajectories that resemble the x (4) family of regular, retrograde orbits. The bow tie orbits appear to be r elated to the 4/1 orbit family discussed by Contopoulous in 1988, but parti cles moving along a bow tie orbit pass very close to the center of the bar twice each orbit. Unlike the barlike configurations that previously have be en constructed using dissipationless, N-body simulation techniques, the eff ective potential of our gasdynamical bar is very shallow and generally does not support the x(1) family of orbits. If primordial galaxies evolve to a rapidly rotating barlike configuration before a significant amount of star formation has taken place and then stars form from the gas that makes up th e bar, the initial stellar distribution function should consist of orbits t hat are (1) supported by the gaseous barlike potential and (2) restricted t o have initial conditions dictated by the gasdynamics of the bar. With this "restriction hypothesis" in mind, we propose that stellar dynamical system s that form from gaseous bars will have characteristics that differ signifi cantly from systems that form from a bisymmetric instability in an initiall y axisymmetric stellar system. Since bow tie orbits are preferred over x(1) orbits, for example, such systems should have a more boxy or peanut shape when seen face-on; there will be a mechanism for funneling material more di rectly into the center of the galaxy; and, near the galaxy center, stars ma y appear to move along retrograde trajectories.