Star Formation-Regulated Growth of Black Holes in Protogalactic Spheroids

The observed relation between central black hole mass and spheroid velocity dispersion is interpreted in terms of a self-regulation model that incorporates a viscous Keplerian accretion disk to feed the black hole, embedded in a massive, self-gravitating star forming disk that eventually populates the spheroid. The model leads to a constant ratio between black hole mass and spheroid mass which is equal to the inverse of the critical Reynolds number for the onset of turbulence in the accretion disk surrounding the central black hole. Applying the fundamental plane correlation for spheroids, we find that the black hole mass has a power-law dependence on the spheroid velocity dispersion with a slope in the range of 4-5. We explain the larger scatter in the Magorrian relation with respect to the black hole mass-spheroid velocity dispersion relationship as a result of secular evolution of the spheroid that primarily affects its luminosity and to a much lesser extent its velocity dispersion.Comment: 12 pages, no figures, submitted to ApJ Letter

A Gravitational Instability-Driven Viscosity in Self-Gravitating Accretion Disks

We derive a viscosity from gravitational instability in self-gravitating accretion disks, which has the required properties to account for the observed fast formation of the first super-massive black holes in highly redshifted quasars and for the cosmological evolution of the black hole-mass distribution.Comment: 14 pages, 1 figure, ApJ Letters (in press

Outflow from and asymmetries in the nebula around the LBV candidate Sk-69 279

We present and discuss new long-slit Echelle spectra of the LMC LBV candidate Sk-69 279 and put them in context with previous images and spectra. While at first glance a simple spherically expanding symmetric shell, we find a considerably more complex morphology and kinematics. The spectra indicate that morphologically identified deviations from sphericity are outflows of faster material out of the main body of Sk-69 279. The morphological as well as the kinematic similarity with other LBV nebulae makes it likely that Sk-69 279 is an LBV candidate, indeed, and poses the question in how far outflows out of expanding LBV nebulae are a general property of such nebulae--at least during some phases of their evolutions

The stability of the Circumnuclear Disk clouds in the Galactic Centre

The influence of rotation and magnetic fields on the physical properties of isothermal gas clouds is discussed. The presence of rotation and/or magnetic fields results in an increase of the critical cloud mass with respect to gravitational instability for clouds of a given temperature and external pressure. Rotating clouds have higher densities. Consequently, they are more stable against tidal shear than non-rotating clouds. They can approach the Galactic Centre up to a radius of ~2 pc without being disrupted by the tidal shear due to the gravitational potential. For smaller radii the clouds either collapse or become tidally disrupted. We suggest that this mechanism is responsible for the formation of the inner edge of the Circumnuclear Disk in the Galactic Centre.Comment: 7 pages with 2 figures. Accepted for publication in A&