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B. Xie, C. Pryor (Rutgers University), M. Hilker (Sternwarte University Bonn), K. Gebhardt (University of Texas at Austin), T. B. Williams (Rutgers University)
We have obtained 12085 velocities for 4728 giants within the central 3.5' of omega Centauri using the Rutgers Fabry-Perot Imaging Spectrometer (FP) on the CTIO 1.5 meter telescope. The median internal uncertainty of the velocity measurements is 1.70 km/s. Metallicities from Stroemgren photometry are available for 1011 stars of the FP sample and we use these to study the correlation between the Stroemgren metallicity and the the velocity dispersion and the projected rotation. We use the metallicities to divide the sample into three bins. The metal-poor sample shows systematic rotation with high confidence, but the most metal-rich group does not. Though the measured projected rotation is not significant, it is suggestive that the position angle of the best-fitting rotation axis of the metal-rich group is about 90 degrees from that of the metal-poor groups. This is consistent with the spatial flattening difference in the metal-poor and metal-rich groups as suggested by Pancino et al. (2001). Our data do not yield significantly different velocity dispersion for the different metallicity groups, unlike what was found by Norris et al. (1997). Our data show no evidence for the large difference in the systemic velocity of the most metal rich sample reported by Ferraro et al. (2002). This research is supported by grant AST-0098650 from the National Science Foundation.
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.