Probing gas kinematics towards the high-mass protostellar object G358.46−0.39

Abstract

ABSTRACTWe investigated the nature of protostellar objects in G358.46−0.39 and their gas kinematics using ALMA data, with the aim of understanding the ongoing star formation activities in the region. The dust continuum map reveals multiple cores (MM1a, MM1b, MM1c, and MM2) dominated by MM1a, with no detectable free–free emission. We calculated the masses and the column densities of the various objects (MM1a, MM1b, MM1c, and MM2). A total of 33, 10, 10, and 9 molecular transitions are detected towards MM1a, MM1b, MM1c, and MM2, respectively. The differences in the number of molecular lines detected towards each of the cores support different excitation conditions at different positions. We derived the kinetic temperature ranges of MM1a, MM1b, MM1c, and MM2 to be ∼96–118, 96–114, 72–74, and 80–84 K, respectively. A highly collimated bipolar outflow traced by 12CO emission is observed to be associated with MM1a, with knots along the outflow lobes, which could be an indication of episodic ejection. The C17O emission is observed to be likely tracing a slowly rotating envelope of gas around MM1a. The velocity field map of CH3OH (22, 1 − 31, 2) emission suggests the presence of a rotating structure, possibly a disc. The physical and kinematic properties of MM1a are strong indication of a massive young stellar object, with ongoing outflow activity and accretion in its early stage of formation.