Masers and Star Formation Activities in W51A

Abstract

Concurrently with the maser flare observed in W51-North during the 3 month monitoring of H _2 O, NH _3 , and CH _3 OH maser variability from 2020 January to April using the Tianma 65 m Radio Telescope, we conducted Very Large Array mappings for these three maser species across the entirety of W51A region. After finding the ring-shaped H _2 O maser which might trace the disk surrounding the protostar residing in W51-North, the NH _3 (9,6) maser delineated a jet which might be illuminated in the luminosity outburst possibly caused by the infalling streamer’s interaction with the protostar’s disk. An analysis of the comprehensive distribution of maser spots allowed us to affirm that W51N4 or ALMAmm31 serves as the primary source of the Lacy jet. Furthermore, we observed that class I methanol maser spots may extend beyond the locations of the H _2 O and NH _3 (9,6) masers within the outflow. Additionally, emissions from other NH _3 maser transitions coincided with specific 1.3 mm continuum sources. The arrangement of H _2 O maser spots in the vicinity of W51e2-E potentially indicates episodic accretions in this source. Combining the data from the Atacama Large Millimeter/submillimeter Array data archive for W51-North, W51e2, and W51e8, we have discovered that the H _2 O, NH _3 , and CH _3 OH masers, as well as the HC _3 N and SiO emissions are found to be good tools for tracing outflow in this work for W51A.

Keywords

• Star formation
• Interstellar masers
• Astrophysical masers
• Young stellar objects
• Protostars