title: ALMA observations of a hot molecular disk around Orion KL Source I

authors: Tomoya Hirota, Mikyoung Kim, Mareki Honma

abstract: We report results of our ALMA cycle 0 observations of H2O lines and continuum emission toward a massive protostar candidate Source I in Orion KL. We found that the vibrationally excited H2O line at 336 GHz shows a velocity gradient perpendicular to the bipolar outflow traced by the thermal SiO lines. The observed PV diagram and the spectral profile of the 336 GHz H2O line can be explained by an edge-on ring-like structure with an enclosed mass of >7 Solar masses and an excitation temperature of >3000 K. Thus, the 336 GHz H2O line can be a good tracer of a hot (>3000 K) molecular gas disk with the diameter of 100 AU scale. We will discuss about physical properties of the disk around Orion KL Source I traced by the H2O lines and continuum emission.