ALMA BAND 8 CONTINUUM EMISSION FROM ORION SOURCE I

We have measured continuum flux densities of a high-mass protostar candidate, a radio source. I in the Orion. KL region (Orion Source I) using the Atacama Large Millimeter/Submillimeter Array (ALMA) at band. 8 with an angular resolution of 0 ''.1. The continuum emission at 430, 460, and 490 GHz associated with Source. I shows an elongated structure along the northwest-southeast direction perpendicular to the so-called low-velocity bipolar outflow. The deconvolved size of the continuum source, 90 au x 20 au, is consistent with those reported previously at other millimeter/submillimeter wavelengths. The flux density can be well fitted to the optically thick blackbody spectral energy distribution, and the brightness temperature is evaluated to be 700-800 K. It is much lower than that in the case of proton-electron or H-free-free radiations. Our data are consistent with the latest ALMA results by Plambeck & Wright, in which the continuum emission was proposed to arise from the edge-on circumstellar disk via thermal dust emission, unless the continuum source consists of an unresolved structure with a smaller beam filling factor.