ALMA observations of the massive molecular outflow G331.512-0.103

TL;DR

This paper presents ALMA Band 7 observations of the energetic and young massive molecular outflow G331.512-0.103, revealing its compact bipolar structure, shocked shell, and high-velocity features, providing insights into early high-mass star formation.

Contribution

First detailed ALMA imaging of the very young, energetic outflow G331.512-0.103, highlighting its structure and kinematics in high-mass star formation.

Findings

Bipolar outflow velocity ~70 km/s

Shocked shell expansion velocity ~24 km/s

Estimated crossing time ~2000 years

Abstract

The object of this study is one of the most energetic and luminous molecular outflows known in the Galaxy, G331.512-0.103. Observations with ALMA Band 7 (350 GHz; 0.86 mm) reveal a very compact, extremely young bipolar outflow and a more symmetric outflowing shocked shell surrounding a very small region of ionized gas. The velocities of the bipolar outflow are about 70 km s^{-1} on either side of the systemic velocity. The expansion velocity of the shocked shell is ~24 km s^{-1}, implying a crossing time of about 2000 yrs. Along the symmetry axis of the outflow, there is a velocity feature, which could be a molecular "bullet" of high-velocity dense material. The source is one of the youngest examples of massive molecular outflow found associated with a high-mass star.