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Session 82 - Spirals & Irregulars.
Display session, Friday, January 09
Exhibit Hall,

[82.17] Orbit Families in Doubly Barred Galaxies

W. Maciejewski, P. Erwin, L. S. Sparke (U. of Wisconsin, Madison)

We examine particle orbits in a galaxy-like potential where a small, fast-tumbling nuclear bar is nested inside a main bar which has a slower pattern speed. We use the concept of a loop (Maciejewski amp; Sparke 1997, ApJL 484, L117): a closed curve which returns to its original position after two bars have come back to the same relative orientation. We find sets of particles that recreate the shapes of both bars. When going inwards toward the galactic center, the x_2 loops of the big bar smoothly transform into the x_1 loops of the small bar, suggesting that the small bar should not be larger than the maximum extent of the x_2 orbits along the big bar. The small bar can easily disrupt orbits supporting the big bar, so its mass should stay below a certain limit to ensure that the galaxy remains doubly barred. We present recent observations of doubly barred galaxies made with the WIYN telescope, and attempt to draw basic conclusions using the links between morphology and dynamics found in our models.

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