The super-massive black holes of 106 to 109 solar masses that reside in the nuclei of active galaxies (AGN) are surrounded by a region emitting broad emission lines, probably associated with an accretion disk, which cannot be resolved spatially. The relative significance of inflow, outflow, rotational, or turbulent motions in the broad-line region as well as their structure (spherical and/or thin/thick accretion disk) are unknown. This study reports a fundamental relation between the observed emission line width and shape in AGN spectra, from which it is inferred that the geometry of the inner region is flattest for the fast-rotating broad-line objects whereas slow-rotating narrow-line AGN have a more spherical structure. Knowing the rotational velocities one can derive more accurately the central black hole masses, which are two to ten times smaller than previously estimated.
- Wolfram Kollatschny
- Matthias Zetzl