Water maser kinematics in massive star-forming regions: Cepheus A and W75N

TL;DR

This study uses VLBI water maser observations to investigate the kinematics of gas near massive protostars in Cepheus A and W75N, revealing multiple star formation centers, early protostellar phenomena, and complex outflow structures.

Contribution

It provides new high-resolution observational insights into the kinematics and phenomena of massive star-forming regions, including the discovery of isotropic ejections and combined outflow structures.

Findings

Identification of multiple high-mass star formation centers at 100 AU scales.

Discovery of isotropic gas ejections in early protostellar stages.

Detection of simultaneous wide-angle outflows and collimated jets in Cep A HW2.

Abstract

VLBI multi-epoch water maser observations are a powerful tool to study the dense, warm shocked gas very close to massive protostars. The very high-angular resolution of these observations allow us to measure the proper motions of the masers in a few weeks, and together with the radial velocity, to determine their full kinematics. In this paper we present a summary of the main observational results obtained toward the massive star-forming regions of Cepheus A and W75N, among them: (i) the identification of different centers of high-mass star formation activity at scales of 100 AU; (ii) the discovery of new phenomena associated with the early stages of high-mass protostellar evolution (e.g., isotropic gas ejections); and (iii) the identification of the simultaneous presence of a wide-angle outflow and a highly collimated jet in the massive object Cep A HW2, similar to what is observed in some low-mass protostars. Some of the implications of these results in the study of high-mass star formation are discussed.