ALMA-QUARKS view of W49N: Multipolar episodic outflow associated with the most energetic Galactic water maser

TL;DR

This study uses high-resolution ALMA observations to analyze a complex, energetic, and episodic multipolar outflow in W49N, revealing new lobes, knots, and signs of precession, indicating shared outflow mechanisms across stellar masses.

Contribution

First detailed ALMA-based analysis of a multipolar, episodic outflow in W49N, identifying new lobes and features that suggest commonality in outflow physics across star-forming environments.

Findings

Discovered four new outflow lobes with jet-like morphology.

Confirmed the outflow as one of the most energetic in the Galaxy.

Detected chains of knots and S-shaped wiggles indicating episodic ejection and precession.

Abstract

We present a detailed investigation of a multipolar episodic molecular outflow in the mini-starburst region W49N, which hosts the most luminous water maser in the Galaxy. Using high-resolution ($\sim$0.3 arcsec) Atacama Large Millimeter/submillimeter Array (ALMA) observations of the $\mathrm{^{12}CO}$ emission as part of the ALMA-QUARKS survey, we analyze the morphology and kinematics of the outflow. Our observations reveal four newly identified outflow lobes in addition to the previously known central bipolar jet. These lobes appear more jet-like rather than exhibiting wide opening angles. Based on the $\mathrm{^{12}CO}$ (2-1) and $\mathrm{^{13}CO}$ (2-1) emission, we provide a more reliable estimate of the outflow's physical parameters, confirming it as one of the most energetic outflows in the Galaxy. Notably, these newly discovered lobes exhibit chains of knots, a characteristic signature of episodic ejection. Furthermore, two of the lobes display prominent S-shaped wiggles, suggestive of a precessing jet. The discovery of these features -- commonly observed in outflows from low-mass protostars -- in such an extreme massive star-forming environment provides compelling evidence that some underlying physical mechanisms for launching outflows are conserved across a wide range of stellar masses.