Structure of the hot molecular core G10.47+0.03

TL;DR

This study uses high-resolution molecular line observations and radiative transfer modeling to reveal the complex physical and chemical structure of the hot molecular core G10.47+0.03, shedding light on early massive star formation processes.

Contribution

It provides detailed spatial distribution of density, temperature, and chemical abundances in G10.47+0.03 using advanced observational and modeling techniques, a novel approach for this core.

Findings

Detection of hundreds of molecular lines, including vibrationally excited HC15N.

Evidence of outflow and infall motions in the core.

Density profile best described by a Plummer radial profile with central flattening.

Abstract

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 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, and myXCLASS for line identification. 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. 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 GHz, revealing central flattening and rapid radial falloff of the density outwards of 10^4 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 the density to be clumpy. We conclude that G10.47+0.03 is characterized by beginning of feedback from massive stars, while infall is ongoing. Large gas masses (hundreds of Msun) are heated to high temperatures, 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 likely responsible for the central flattening of the density.