Stellar Proper Motions in the Central 0.1 Parsec of the Galaxy

A. Eckart and R. Genzel

Max-Planck Institut für extraterrestrische Physik Garching, FRG

Paper: Nature 383, 415


Abstract:

We report the first results of a program to measure proper motions of stars in the innermost core of the Galaxy. From high resolution near-infrared imaging over the last 4 years we have determined proper motions for 39 stars between 0.03 and 0.3 pc from the compact radio source SgrA*. For 19 of these the derived motions are more significant than 4s 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 the dynamic evidence is now strong that there is a 2.45(+/-0.4)x1e6 Mo central dark mass located within <0.015 pc of SgrA*. Its mass density is at least 6.5x1e9 Mo pc-3 excluding that the central mass concentration is in form of a compact white dwarf or neutron star cluster. In addition, we have detected significant changes in the structure of the innermost complex of stars in the immediate vicinity of SgrA*, implying in at least one case stellar motions of ~1500 km/s within ~0.01 pc of the compact radio source. Including this preliminary evidence, the inferred density of the central dark mass would then have to be in excess of 1e12 Mo pc-3, implying that the central mass concentration is likely a single massive black hole.


Preprints available from the authors at genzel@mpe-garching.mpg.de .

Back to the gcnews home-page.