Slow ionized wind and rotating disklike system associated with the high-mass young stellar object G345.4938+01.4677

TL;DR

This study uses ALMA observations to characterize a slow ionized wind and rotating molecular core around a high-mass young stellar object, revealing Stark broadening in hydrogen lines and evidence of core rotation.

Contribution

First detailed modeling of a slow ionized wind with Stark broadening signatures in a high-mass young star system using ALMA data.

Findings

Detection of hydrogen recombination lines with Stark broadening signatures.

Identification of a rotating molecular core perpendicular to the jet axis.

Evidence of a slow photo-ionized wind without high-velocity components.

Abstract

We report the detection, made using ALMA, of the 92 GHz continuum and hydrogen recombination lines (HRLs) H40$\alpha$, H42$\alpha$, and H50$\beta$ emission toward the ionized wind associated with the high-mass young stellar object G345.4938+01.4677. This is the luminous central dominating source located in the massive and dense molecular clump associated with IRAS 16562$-$3959. The HRLs exhibit Voigt profiles, a strong signature of Stark broadening. We successfully reproduce the observed continuum and HRLs simultaneously using a simple model of a slow ionized wind in local thermodynamic equilibrium, with no need a high-velocity component. The Lorentzian line wings imply electron densities of $5\times10^7$ cm$^{-3}$ on average. In addition, we detect SO and SO$_2$ emission arising from a compact ($\sim3000$ AU) molecular core associated with the central young star. The molecular core exhibits a velocity gradient perpendicular to the jet-axis, which we interpret as evidence of rotation. The set of observations toward G345.4938+01.4677 are consistent with it being a young high-mass star associated with a slow photo-ionized wind.