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Newly determined high-precision relative proper motions determined from the Hubble Space Telescope Wide Field Planetary Camera 2 are used along with radial velocity measurements to determine the dynamical distance to the globular cluster M15. A comparison of the proper motion and radial velocity dispersions from a sample of 237 stars, located at an average radial distance of about 10" from the cluster center, yields a cluster distance of 9.98+/-0.47 kpc. This distance agrees to within the stated errors to other distance estimates but places this object about 5% closer than the currently adopted value of 10.4 kpc. Using this new distance, we estimate that RR Lyrae stars having [Fe/H]=-2.15 have a value of M-v(RR)=0.51+/-0.11. We also estimate that M 15 has an age of about 13.2 Gyr, which places it among the oldest of the Galactic globular clusters. From a comparison of the observed velocity dispersion with results from recent N-body calculations, we derive a total cluster mass for M 15 of M-C=4.5x10(5) M-circle dot

Topics:
Distance scale, Globular clusters : individual (M15), Globular-Clusters, Astrometric Distances

Publisher: Institute of Physics Publishing

Year: 2004

OAI identifier:
oai:espace.library.uq.edu.au:UQ:265881

Provided by:
University of Queensland eSpace

Downloaded from
http://espace.library.uq.edu.au/view/UQ:265881/UQ265881_OA.pdf