SMA Observations of the Hot Molecular Core IRAS 18566+0408

We present Submillimeter Array (SMA) observations toward the high-mass star-forming region IRAS 18566+0408. Observations at the 1.3 mm continuum and in several molecular line transitions were performed in the compact (2.″4 angular resolution) and very-extended (∼0.″4 angular resolution) configurations. The continuum emission from the compact configuration shows a dust core of 150 M _⊙, while the very-extended configuration reveals a dense (2.6 × 10⁷ cm^-3) and compact (∼4000 au) condensation of 8 M _⊙. We detect 31 molecular transitions from 14 species including CO isotopologues, SO, CH₃OH, OCS, and CH₃CN. Using the different k-ladders of the CH₃CN line, we derive a rotational temperature at the location of the continuum peak of 240 K. The {}¹²{CO}(2-1), {}¹³{CO}(2-1), and {SO}({6}₅{--}{5}₄) lines reveal a molecular outflow at PA ∼ 135° centered at the continuum peak. The extended {}¹²{CO}(2-1) emission has been recovered with the IRAM 30 m telescope observations. Using the combined data set, we derive an outflow mass of 16.8 M _⊙. The chemically rich spectrum and the high rotational temperature confirm that IRAS 18566+0408 is harboring a hot molecular core. We find no clear velocity gradient that could suggest the presence of a rotational disk-like structure, even at the high-resolution observations obtained with the very-extended configuration.