Control Number
Presentation Preference
Proper Motions of the SiO Masers Surrounding the Young Stellar Object Orion Source I
Author Block
Lynn D. Matthews1, C. Goddi1, L. J. Greenhill1, C. J. Chandler2, E. M. L. Humphreys1, M. J. Reid1
1Harvard-Smithsonian, CfA, 2National Radio Astronomy Observatory.
18. Star Formation
Investigations of the dynamics of material <100 AU from high mass young stellar objects (YSOs) are crucial for constraining models of high mass star formation. These are the scales over which accretion is expected to occur and over which outflows are expected to be launched and collimated. As part of the KaLYPSO project (, our group has been using Very Baseline Array (VLBA) observations of SiO v=1 & 2, J=1-0 masers to investigate gas motions within 10-100 AU of the nearest high-mass YSO, Source I in the Orion BN/KL region. We will present proper motion measurements of SiO maser spots based on 19 epochs of data spanning a 22-month period. We find maser spots that persist up to several months and whose motions in the plane of the sky range from ~1-20 km/s. The observed spot motions indicate both rotation and outflow/expansion of the molecular gas surrounding Source I. Our results support a picture in which the SiO masers arise either from a flared, rotating, disk seen nearly edge-on, or the interface between a disk and an expanding wind/outflow oriented along the northeast/southwest direction.
This work is funded by grant 0507478 from the National Science Foundation.

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