Supercritical accretion and ULXs - what can we achieve?

Supercritical (or super-Eddington) accretion seems to occur in various black hole objects, including microquasars and ultra-luminous X-ray sources. We, here, elucidate the theory of supercritical accretion flow based on our two-dimensional (2-D) global radiation-hydrodynamic (RHD) and radiation-magnetohydrodynamic (RMHD) simulations. We first confirm that there is practically no limit to the accretion rate onto black holes. We then discuss several noteworthy observable features of the supercritical flow; that is, mild beaming, relativistic, collimated outflow, and inverse-Compton scattering spectra by optically thick outflow. For face-on observers the maximum apparent (isotropic) luminosities of ∼ 22 L_E (with L_E being the Eddington luminosity) can be achieved for the mass supply rate of ∼ 50 L_E/c². Even larger isotropic luminosities are possible for higher mass supply rates. For edge-on observers, conversely, the apparent luminosity will be much less. It will be even lower, if the the innermost bright part of the disk is obscured by the outer part. High velocity (> 0.5 c) jet accelerated by radiation-pressure force and collimated by Lorentz force is also expected. We expect large kinetic luminosity, ∼ 0.1 L_E, and high mass outflow rate, ∼ 10 L_E/c². This may account for large ionizing nebulae around ULXs.