A Rotating Molecular Disk Toward Iras 18162-2048, the Exciting Source of Hh 80-81

We present several molecular line emission arcsecond and subarcsecond observations obtained with the Submillimeter Array in the direction of the massive protostar IRAS 18162–2048, the exciting source of HH 80–81. The data clearly indicate the presence of a compact (radius ≈425–850 AU) SO 2 structure, enveloping the more compact (radius ≲150 AU) 1.4 mm dust emission (reported in a previous paper). The emission spatially coincides with the position of the prominent thermal radio jet which terminates at the HH 80–81 and HH 80N Herbig–Haro objects. Furthermore, the molecular emission is elongated in the direction perpendicular to the axis of the thermal radio jet, suggesting a disk-like structure. We derive a total dynamic mass (disk-like structure and protostar) of 11–15 M ☉ . The SO 2 spectral line data also allow us to constrain the structure temperature between 120 and 160 K and the volume density ≳ 2 × 10 9 cm −3 . We also find that such a rotating flattened system could be unstable due to gravitational disturbances. The data from C 17 O line emission show a dense core within this star-forming region. Additionally, the H 2 CO and SO emissions appear clumpy and trace the disk-like structure, a possible interaction between a molecular core and the outflows, and in part, the cavity walls excavated by the thermal radio jet.