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M.N. Fanelli (U. of North Texas), W.H. Waller (Tufts), P.M. Marcum (TCU), R.W. O'Connell (UVa), T.P. Stecher (NASA/GSFC)
Comparative imaging at ultraviolet (1200-3200 A) and optical wavelengths can provide vital clues to the processes which organize star formation in galaxies. Here, we present results from our program combining UV imagery from UIT and HST with comparable-resolution images in the UBVRI and H\alpha bands.
Spiral structure in galaxy disks is often attributed to one or more density-wave modes that are driven by various asymmetries in the disks (e.g. bars) or in the disk environment (e.g. satellite galaxies). However, tidal effects induced by gravitating interlopers may also yield spiral structures. To distinguish between tidal and modal dynamics, one must determine whether the observed features are material constructs or propagating wavefronts. We define observational signatures discriminating between these situations and apply these to some nearby galaxies.
Star-forming rings are common seen in early and intermediate-type disk galaxies. Such ring-like concentrations of gas and associated star formation may have helped to build the inner parts of primeval disk galaxies, as evidenced by the discovery of a starburst-ring galaxy at z~1.5. The formation and maintenance of these starburst rings are often attributed to orbital resonances with rotating bar or "oval" asymmetries in the stellar disks. Such resonant dynamics are indicated by an analysis of the nearest ringed galaxy, NGC~4736 (M94).
The author(s) of this abstract have provided an email address for comments about the abstract: fanelli@unt.edu