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S. E. Meidt, R. J. Rand (University of New Mexico)
Spiral galaxies displaying molecule-dominated ISMs are potential candidates for pattern speed determination by the Tremaine-Weinberg method (1984); the molecular gas of such galaxies, as traced by CO emission, is argued to approximately obey the continuity equation on orbital timescales—a key requirement of the method. We continue our work on this application of the Tremaine-Weinberg method with pattern speed determinations of several galaxies using CO emission data cubes from the BIMA SONG survey. Because the reliability of a method such as this depends on the presence of a pattern, we select the galaxies in our sample by visual inspection and by the use of Fourier decompositions of deprojected surface brightness intensities as a means of examining whether a large-scale pattern exists. Molecular dominance is addressed using the results of Wong and Blitz (2002), wherein radial profiles indicate that some of the galaxies in our sample are molecule-dominated in the region of CO detection. We also use their finding that HI column densities are generally \lesssim 10 M\sun/pc2 as evidence for molecule-dominated ISMs in other sample galaxies.
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Bulletin of the American Astronomical Society, 37 #2
© 2005. The American Astronomical Soceity.