Stellar proper motions in the central 0.1 pc of the Galaxy

We report the first results of a programme to measure proper motions of stars in the innermost core of the Galaxy. From high-resolution near-infrared imaging over the last four years we have determined proper motions for 39 stars between 0.03 and 0.3 pc from the compact radio source Sgr A*. For 19 of these the derived motions are more significant than 4σ in at least one coordinate. Proper motion and radial velocity dispersions are in very good agreement, indicating that the stellar velocity field on average is close to isotropic. Taking radial and proper motion data together implying that the central mass concentration is probably a single massive black hole.