Submillimeter Array Observations of the Molecular Outflow in High-mass Star-forming Region G240.31+0.07

TL;DR

This study presents detailed submillimeter observations of a massive star-forming region, revealing a large, bipolar molecular outflow driven by a central core, supporting the idea that high-mass stars form similarly to low-mass stars but on a larger scale.

Contribution

First detailed imaging of a wide-angle, massive molecular outflow in a high-mass star-forming region, demonstrating scaled-up low-mass star formation processes.

Findings

The outflow has ~98 Msun of molecular gas, making it one of the most massive known.

The outflow exhibits a high mass-loss rate of 4.1×10^{-3} Msun/yr.

The central core likely hosts the outflow's driving source.

Abstract

We present Submillimeter Array observations toward the 10^{4.7} Lsun star-forming region G240.31+0.07, in the J=2-1 transition of 12CO and 13CO and at 1.3 mm continuum, as well as the 12CO and 13CO observations from the Caltech Submillimeter Observatory to recover the extended emission filtered out by the interferometer. Maps of the 12CO and 13CO emission show a bipolar, wide-angle, quasi-parabolic molecular outflow, roughly coincident with an IR nebula revealed by the Spitzer 3.6 and 4.5 micron emission. The outflow has ~98 Msun molecular gas, making it one of the most massive molecular outflows known, and resulting in a very high mass-loss rate of 4.1 by 10^{-3} Msun yr^{-1} over a dynamical timescale of 2.4 by 10^4 yr. The 1.3 mm continuum observations with a 4" by 3" beam reveal a flattened dusty envelope of ~150 Msun, which is further resolved with a 1.2" by 1" beam into three dense cores with a total mass of ~40 Msun. The central mm core, showing evidence of active star formation, approximately coincides with the geometric center of the bipolar outflow thus most likely harbors the powering source of the outflow. Overall our observations provide the best case to date of a well-defined wide-angle molecular outflow in a >10^4 Lsun star-forming region. The outflow is morphologically and kinematically similar to low-mass protostellar outflows but has two to three orders of magnitude greater mass, momentum, and energy, and is apparently driven by an underlying wide-angle wind, hence further supports that high-mass stars up to late-O types, even in a crowded clustering environment, can form as a scaled-up version of low-mass star formation.