Evn Observations of H2O Masers Towards the High-Mass Young Stellar Object in Afgl 5142

Abstract

We have conducted multi-epoch EVN observations of the 22.2 GHz water masers towards the high-mass young stellar object in AFGL 5142. With four observing epochs, spanning a time of ∼1 year, 12 distinct maser features have been detected and accurate values of the proper motions are derived for those persistent over three or four epochs. On the basis of their spatial distribution, the observed maser features can be divided into two groups. A model fit to the positions and velocities of the maser features of Group I, detected in the same region (within ∼500 mas) where the massive YSO should be located, demonstrates that these might arise on the surface of a nearly edge-on Keplerian disk, rotating around a massive young stellar object. The maser features of Group II, found at large distances from the YSO (≥ 1″), have positions and line-of-sight velocities in agreement with the blue-shifted lobe of a large-scale molecular outflow, and might result from the interaction between the gas flowing away from the young stellar object and the ambient gas of the progenitor molecular core.