The quasi-steady structure of super-critical accretion flows around a black
hole is studied based on the two-dimensional radiation-hydrodynamical (2D-RHD)
simulations. The super-critical flow is composed of two parts: the disk region
and the outflow regions above and below the disk. Within the disk region the
circular motion as well as the patchy density structure are observed, which is
caused by Kelvin-Helmholtz instability and probably by convection. The
mass-accretion rate decreases inward, roughly in proportion to the radius, and
the remaining part of the disk material leaves the disk to form outflow because
of strong radiation pressure force. We confirm that photon trapping plays an
important role within the disk. Thus, matter can fall onto the black hole at a
rate exceeding the Eddington rate. The emission is highly anisotropic and
moderately collimated so that the apparent luminosity can exceed the Eddington
luminosity by a factor of a few in the face-on view. The mass-accretion rate
onto the black hole increases with increase of the absorption opacity
(metalicity) of the accreting matter. This implies that the black hole tends to
grow up faster in the metal rich regions as in starburst galaxies or
star-forming regions.Comment: 16 pages, 12 figures, accepted for publication in ApJ (Volume 628,
July 20, 2005 issue