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

Abstract

We present a detailed investigation of a multipolar episodic molecular outflow in the ministarburst region W49N, which hosts the most luminous water maser in the Galaxy. Using high-resolution ( ∼0.″3 ) Atacama Large Millimeter/submillimeter Array (ALMA) observations of the 12CO 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 jetlike rather than exhibiting wide opening angles. Based on the 12CO (2─1) and 13CO (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.