Fabry-Perot Observations of Globular Cluster Cores
Session 74 -- Globular Clusters
Display presentation, Friday, January 14, 9:30-6:45, Salons I/II Room (Crystal Gateway)

## [74.03] Fabry-Perot Observations of Globular Cluster Cores

C. Pryor, K. Gebhardt, T.B. Williams (Rutgers University), J. E. Hesser (DAO/HIA/NRC)

\def\kms{$\rm {km}~\rm s^{-1}$}

We have used an Imaging Fabry-Perot(FP) Interferometer to study the kinematics of the cores of globular clusters. We have obtained a total of 1200 individual stellar velocities in the central regions of the clusters M15, 47~Tuc, N6397, M30, and N6752. The FP has proven to be a very efficient technique in these dense regions since we are able to measure hundreds of velocities with about 4 hours of observing time for each cluster. Using our data and published velocities at larger radii, we have measured the projected velocity dispersion profile. A common feature among the clusters is that the dispersion profile flattens in the central regions.

The FP can also be used to study the integrated cluster light to provide a small-scale velocity map of the cluster. The FP has an advantage over other integrated light studies since we are better able to decrease the contribution from a few bright stars which might otherwise tend to dominate the integrated light measurement (see Gebhardt et al. 1994, AJ, submitted, and Dubath 1993, Ph.D. Thesis, University of Geneva). From the velocity map, we have measured rotation in the inner 6\arcsec\ for the clusters analysed so far, M15 and 47~Tuc. Using the stellar velocities, we have also measured rotation at a radius of 30\arcsec. For both clusters, the rotation amplitude does not change with radius. The constancy of the rotation amplitude is not consistent with the solid body rotation which one might naively expect in the dense central region of these cluster, which have a short two-body relaxation time.