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R. Wilhelm (Texas Tech University), L. Groning (Southwestern University), G. Edmiston (Texas Tech University)
The study of extended tidal tails in globular clusters can yield important discoveries about the nature of the Galactic halo and the disruption rates of the clusters. Tails can be used to contrain, the orbital parameters for a cluster, the evaporation rate of the cluster, and the percentage of former cluster stars now in the halo field. NGC 6934 is one of numerous Galactic globular clusters which have been shown, from statistical star counts, to have extended tidal tails that reach far beyond the classical King tidal radius. NGC 6934 is an exceptional candidate for a kinematic survey to probe the existence of such tails, because it has a line-of-sight velocity (Vlos = -412 km/s) which is far different from the average for the halo.
We will be presenting kinematic results for a sample of 303 tidal candidates which extend out to one degree along the previously identified N-W tidal extension. The sample covers a range of magnitudes (14.0 < V < 17.5) with a faint magnitude cutoff slightly below the horizontal branch of the cluster. The data was taken using Hydra/MOS on the WIYN 3.5m telescope at KPNO. The medium resolution (1.4 Å) spectroscopy was sufficient to determine radial velocities to within ± 10 km/s. Results show no stars from this sample having cluster-like velocities beyond the King tidal radius. New BVRI photometry taken from the 0.8m telescope at McDonald Observatory has been used to determine distances and metal abundance for the sample stars, which include members of the thin disk, thick disk, halo and NGC 6934 cluster stars. We will also present photometry which extends the faint magnitude limit of tidal tail survey to V ~ 19.5.
If you would like more information about this abstract, please follow the link to http://www.phys.ttu.edu/~wilhelm/. This link was provided by the author. When you follow it, you will leave the Web site for this meeting; to return, you should use the Back comand on your browser.
The author(s) of this abstract have provided an email address for comments about the abstract: ron.wilhelm@ttu.edu
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.