The Tremaine-Weinberg Method for Pattern Speeds Using Hα Emission from Ionized Gas

Beckman, J. E.; Fathi, K.; Piñol, N.; Toonen, S.; Hernandez, O.; Carignan, C.
Bibliographical reference

Formation and Evolution of Galaxy Disks ASP Conference Series, Vol. 396, Proceedings of the conference held 1-5 October, 2007 at the Centro Convegni Matteo Ricci, Rome, Italy. Edited by José G. Funes, S.J., and Enrico Maria Corsini. San Francisco: Astronomical Society of the Pacific, 2008., p.353

Advertised on:
10
2008
Number of authors
6
IAC number of authors
0
Citations
1
Refereed citations
1
Description
The Fabry-Perot interferometer FaNTOmM was used at the 3.6-m CFHT and the 1.6-m Mont Mégantic Telescope to obtain data cubes in Hα of 9 nearby spiral galaxies from which maps in integrated intensity, velocity, and velocity dispersion were derived. We then applied the Tremaine-Weinberg method, in which the pattern speed can be deduced from its velocity field, by finding the integrated value of the mean velocity along a slit parallel to the major axis weighted by the intensity and divided by the weighted mean distance of the velocity points from the tangent point measured along the slit. The measured variables can be used either to make separate calculations of the pattern speed and derive a mean, or in a plot of one against the other for all the points on all slits, from which a best fit value can be derived. Linear fits were found for all the galaxies in the sample. For two galaxies a clearly separate inner pattern speed with a higher value, was also identified and measured.