Determination of the mass distribution in galactic centers

We investigate how well one can determine the gravitational potential in ga lactic centers from an analysis of the observed line-of-sight velocities of interstellar material, e.g. (giant) molecular clouds. In this paper, we ai m to demonstrate the principle of our approach. Therefore, we use simulated sets of data. We model the mass distribution as a combination of a point-l ike central mass and an extended component. We calculate the observable dis tribution of line-of-sight velocities in the corresponding gravitational po tential for different global flow patterns (purely circular motion, accreti on disks, in-and outflows). We fit this data to previously unknown flow pat terns and determine the degree of accuracy of the mass parameters by means of a Monte Carlo technique. We find that the best fit mass parameters typic ally differ from the true parameters by factors of 1 to 5 (with mass-parame ters as expected for Seyfert Galaxies, a spectral resolution of 20 km/s, an d a spatial distribution of 50 observed clouds within 300 pc), in some case s even more. This implies that, in addition to purely circular motion, othe r flow patterns should be considered when interpreting real data. (C) 1999 Elsevier Science B.V. All rights reserved.