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P. Zimmer, R. Rand (Univ. of New Mexico)
We explore the use of the Tremaine-Weinberg method, using single dish CO maps, to determine the spiral pattern speed of M51. The method integrates the continuity equation to yield the pattern speed, \OmegaP, from the intensity and velocity structure of a continuous tracer. We have used molecular gas as the tracer, since in a galaxy with a molecule dominated ISM such as M51, the molecular gas should obey the continuity equation to first order. We also explore the effects of the conversion factor from CO brightness to molecular column density on the results, both with a radial gradient in the conversion factor as well as an arm-interarm contrast.
The author(s) of this abstract have provided an email address for comments about the abstract: zimm@as.unm.edu