Radiation hydrodynamic simulations of a super-Eddington accretor as a model for ultra-luminous sources

We perform two-dimensional radiation hydrodynamic (RHD) simulations of superEddington accretion flow and the accompanying outflow to investigate how they will be observed from various viewing directions. We consider gas flow around a 10 M-circle dot black hole for mass injection rates of. M-inj/M-Edd = 10(2), 10(3), and 10(4) (in units of M-Edd = L-Edd/c(2), with L-Edd and c being the Eddington luminosity and the speed of light, respectively), and solve gas dynamics and radiation transfer around the black hole, taking into account inverse Compton scattering. We confirm the tendency that the higher the mass accretion rate is, the larger the relative importance of outflow over accretion flow becomes. The observational appearance of the super-Eddington flow is distinct, depending on whether it is viewed from the edge-on direction or from the face-on direction. This is because nearly edge-on observers can only see the outer, cooler (similar to 10(6) K) surface of the inner, vertically inflated part of the flow. Observational properties are briefly discussed in the context of the ultra-luminous X-ray sources (ULXs), the extreme ULXs (E-ULXs), and the ultra-luminous supersoft sources (ULSs). We find that the extremely high luminosities of E-ULXs (L similar to 10(41) erg s(-1)) can be explained when the flow on to the black hole with >= 20M(circle dot) with a very high accretion rate,. m(acc)(=M-acc/M-Edd) greater than or similar to 10(3), is observed from the nearly face-on direction. The high luminosity (similar to 10(39) erg s(-1)) and the very soft blackbodylike spectra with temperatures around 0.1 keV, which are observed in the ULSs, can be explained if the super-Eddington flow with m(acc) similar to 10(2)-10(3) is viewed from large viewing angles, theta greater than or similar to 30 degrees.