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Paper: Detection of a Hot Molecular Disk Around a Massive Protostar Candidate Orion KL Source I
Volume: 499, Revolution in Astronomy with ALMA: The Third Year
Page: 225
Authors: Hirota, T.; Kim, M.; Kurono, Y.; Honma, M.
Abstract: We report results of ALMA cycle 0 observations of the H2O lines at 321 GHz and 336 GHz around a massive protostar candidate Source I in Orion KL. The 336 GHz line is in a vibrationally excited state at the lower state energy of 2939 K. These maps show velocity gradients perpendicular to the bipolar outflow suggesting an existence of a rotating disk. The distribution of the 321 GHz line is found to be similar to that of vibrationally excited SiO masers tracing the base of the outflow emanating from the disk surface. In contrast, the 336 GHz line is emitting from the disk midplane with a diameter of 0.2″ (84 AU) as traced by radio continuum emission. The observed velocity gradient 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 >7M and an excitation temperature of >3000 K. We also investigate the spectral energy distribution of Source I from centimeter to submillimeter wavelengths. Detailed physical and dynamical properties of Source I can be discussed with a spatial scale of smaller than 100 AU.
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