VERY LARGE TELESCOPE KINEMATICS FOR OMEGA CENTAURI: FURTHER SUPPORT FOR A CENTRAL BLACK HOLE

Abstract

The Galactic globular cluster. Centauri is a prime candidate for hosting an intermediate- mass black hole. Recent measurements lead to contradictory conclusions on this issue. We use VLT- FLAMES to obtain new integrated spectra for the central region of. Centauri. We combine these data with existing measurements of the radial velocity dispersion profile taking into account a new derived center from kinematics and two different centers from the literature. The data support previous measurements performed for a smaller field of view and show a discrepancy with the results from a large proper motion data set. We see a rise in the radial velocity dispersion in the central region to 22.8 +/- 1.2 km s(-1), which provides a strong sign for a central black hole. Isotropic dynamical models for. Centauri imply black hole masses ranging from 3.0 x 10(4) to 5.2 x 10(4) M(circle dot) depending on the center. The best-fitted mass is (4.7 +/- 1.0) x 10(4) M(circle dot).