Previous | Session 10 | Next
R.D. Grouchy, R.J. Buta (U. of Alabama)
We present a preliminary analysis of galaxies with strong stellar rings that lack evidence of an obvious bar. It is generally accepted that rings form through the accumulation of gas into orbits in resonance with a strong bar (Buta and Combes, 1996, Fund. Cos. Phys. 17, 95). Therefore, it is an interesting enigma that a non-negligible fraction of non-barred galaxies also show rings and even multiple rings. This group of galaxies could potentially bring a better understanding of how disk galaxies form and evolve through time. Perhaps these galaxies were once strongly barred, creating the ring feature, and have since lost their strong bar. It is also possible that these rings were created through minor mergers or interactions with small companions. We are attempting to understand the mode of ring formation by studying broadband, narrow band, and spectroscopic data for a sample of 40 non-barred ringed galaxies selected from the Third Reference Catalog of Bright Galaxies (RC3, de Vaucouleurs et al. 1991) and the Catalog of Southern Ringed Galaxies (CSRG, Buta, 1995, ApJS, 96, 39). These galaxies display a large dispersion in metric and other properties indicating their rings may have formed through a variety of means. The sample includes CSRG galaxy ESO 297-27, which displays extremely rare \it{counterwinding spiral structure}, in which two sets of non-overlapping spiral arms appear to unwind in opposite directions. This unusual structure has, as of yet, been seen only in non-barred ringed galaxies (Buta, Byrd, and Freeman, 2003, AJ, 125, 634).
Previous | Session 10 | Next
Bulletin of the American Astronomical Society, 37 #2
© 2005. The American Astronomical Soceity.