Context. 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.
Aims: We aim at constraining the spatial distribution of density, temperature, velocity field, and chemical abundances in the hot molecular core G10.47+0.03.
Methods: With the SubMillimeter Array (SMA), we obtained high spatial and spectral resolution of a multitude of molecular lines at different frequencies, including at 690 GHz. At 345 GHz, our beam size is 0.3'', corresponding to 3000 AU. 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.
Results: We find hundreds of molecular lines from complex molecules and high excitations. Even vibrationally excited HC15N at 690 GHz 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 345/355 GHz, revealing central flattening and rapid radial falloff of the density outwards of 104 AU, 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.
Conclusions: 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 300 K, 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.
Astronomy and Astrophysics
- Pub Date:
- December 2011
- ISM: molecules;
- ISM: structure;
- ISM: clouds;
- stars: formation;
- Astrophysics - Astrophysics of Galaxies
- 22 pages, 22 figures, accepted for publication in A&