Multi-Maser VLBI structure of the high-mass SFR G16.59-0.05

Abstract

In the following we summarize our results based on multi-epoch, phase referenced, Very Long Baseline Interferometry (VLBI) observations of maser associations towards the high-mass Star Forming Region (SFR) G16.59-0.05. We observed H2O 22.2 GHz (4 epochs) and OH 1.6 GHz (1 epoch) masers using the Very Long Baseline Array (VLBA), and 3 epochs of CH3OH 6.7 GHz masers with the European VLBI Network (EVN). This source is part of a sample that we are studying aiming to better constraint the process of Massive Star Formation (MSF). Maser emission in high-mass SFRs is associated with the earliest evolutionary stages of massive star formation (e.g. [3]). In particular, different maser species appear to trace distinct environments (e.g. [6]). Using single-epoch VLBI observations it is possible to derive the absolute position and the line of sight (L.O.S.) velocity of the maser spots. Furthermore, multi-epoch VLBI experiments allow us to derive the proper motion of such spots, i.e. to determine the 3-D kinematics of the innermost gas around the associated Young Stellar Objects (YSOs). The synergy between interferometric observations of thermal lines and VLBI observations of maser transitions allows us to investigate the SFR environment on scales ranging from the parsec scale to a few AU.