The nuclear star cluster of the Milky Way is a unique target in the Universe. Contrary to extragalactic nuclear star clusters, using current technology it can be resolved into tens of thousands of individual stars. This allows us to study in detail its spatial and velocity structure as well as the different stellar populations that make up the cluster. Moreover, the Milky Way is one of the very few cases where we have rm evidence for the co-existence of a nuclear star cluster with a central supermassive black hole, Sagittarius A*. The number density of stars in the Galactic center nuclear star cluster can be well described, at distances & 1 pc from Sagittarius A*, by a power-law of the form (r) / r� with an index of 1:8. In the central parsec the index of the power-law becomes much flatter and decreases to 1:2. We present proper motions for more than 6000 stars within 1 pc in projection from the central black hole. The cluster appears isotropic at projected distances & 0:5 pc from Sagittarius A*. Outside of 0.5 pc and out to 1:0 pc the velocity dispersion appears to stay constant. A robust result of our Jeans modeling of the data is the required presence of 0:5 � 2:0 106M of extended (stellar) mass in the central parsec of the Galaxy.

Date of creation, presentation, or exhibit



Proceedings from The Universe Under the Microscope - Astrophysics at High Angular Resolution", held 21-25 April 2008, in Bad Honnef, Germany

This is an author-created, un-copyedited version of an article accepted for publication/published in Journal of Physics: Conference Series. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at

© 2008 IOP Publishing Ltd.

Conference Series 131 (2008) 9 pgs Also archived in arXiv:0810.0204 v1 Oct 1, 2008.

Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works in February 2014.

Document Type

Conference Paper

Department, Program, or Center

School of Physics and Astronomy (COS)


RIT – Main Campus