Observations of 6.7 GHz methanol masers with East-Asian VLBI Network. II. Internal proper motion measurement in G006.79−00.25

Abstract

Abstract We detected internal proper motions of the methanol maser features at 6.7 GHz in a high-mass star-forming region G006.79−00.25 with the East-Asian VLBI Network. The spatial distribution of the maser features shows an elliptical morphology. The internal proper motions of 17 methanol maser features relative to the barycenter of the features were measured. The amplitude of the internal motions ranged from 1.30 to 10.25 km s−1. Most of the internal proper motions of the maser features seem to point counterclockwise along the elliptical morphology of the maser features. We applied the disk model, which includes both rotating and expanding components, to the observed positions, l.o.s. velocities, and proper motions. The derived rotation, expansion, and systemic velocities are $+3^{+2}_{-2}$, $+6^{+2}_{-2}$, and $+21^{+2}_{-2}\:$km s−1, respectively, at the radius of 1260 au on the disk with a position angle of the semi-major axis of − 140° and an inclination of 60°. The derived rotating motion suggests that the methanol maser emissions showing the elliptical spatial morphology possibly trace the rotating disk. The derived expanding motion might be caused by the magnetic-centrifugal wind on the disk, which was estimated on the basis of the typical magnetic field strength at emitting zones of a methanol maser.