SMA Observations of the Hot Molecular Core IRAS 18566+0408

Abstract

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 <SUB>☉</SUB>, while the very-extended configuration reveals a dense (2.6 × 10<SUP>7</SUP> cm<SUP>-3</SUP>) and compact (∼4000 au) condensation of 8 M <SUB>☉</SUB>. We detect 31 molecular transitions from 14 species including CO isotopologues, SO, CH<SUB>3</SUB>OH, OCS, and CH<SUB>3</SUB>CN. Using the different k-ladders of the CH<SUB>3</SUB>CN line, we derive a rotational temperature at the location of the continuum peak of 240 K. The {}<SUP>12</SUP>{CO}(2-1), {}<SUP>13</SUP>{CO}(2-1), and {SO}({6}<SUB>5</SUB>{--}{5}<SUB>4</SUB>) lines reveal a molecular outflow at PA ∼ 135° centered at the continuum peak. The extended {}<SUP>12</SUP>{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 <SUB>☉</SUB>. 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.