2011A&A...536A..33R

The physical structure of hot molecular cores, where forming massive stars have heated up dense dust and gas, but have not yet ionized the molecules, poses a prominent challenge in the research of high-mass star formation and astrochemistry. We aim at constraining the spatial distribution of density, temperature, velocity field, and chemical abundances in the hot molecular core G10.47+0.03. With the SubMillimeter Array (SMA), we obtained high spatial and spectral resolution of a multitude of molecular lines at different frequencies, including at 690GHz. At 345GHz, our beam size is 0.3'', corresponding to 3000AU. We analyze the data using the three-dimensional dust and line radiative transfer code RADMC-3D for vibrationally excited HCN, and myXCLASS for line identification. We find hundreds of molecular lines from complex molecules and high excitations. Even vibrationally excited HC¹⁵N at 690GHz is detected. The HCN abundance at high temperatures is very high, on the order of 10^–5 relative to H₂. Absorption against the dust continuum occurs in twelve transitions, whose shape implies an outflow along the line-of-sight. Outside the continuum peak, the line shapes are indicative of infall. Dust continuum and molecular line emission are resolved at 345/355GHz, revealing central flattening and rapid radial falloff of the density outwards of 10⁴AU, best reproduced by a Plummer radial profile of the density. No fragmentation is detected, but modeling of the line shapes of vibrationally excited HCN suggests that the density is clumpy. We conclude that G10.47+0.03 is characterized by beginning of feedback from massive stars, while infall is ongoing. High gas masses (hundreds of M_☉) are heated to high temperatures above 300K, aided by diffusion of radiation in a high-column-density environment. The increased thermal, radiative, turbulent, and wind-driven pressure drives expansion in the central region and is very likely responsible for the central flattening of the density.