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325 GHz Water Masers in Orion Source I

Published online by Cambridge University Press:  24 July 2012

Florian Niederhofer ,
Elizabeth Humphreys ,
Ciriaco Goddi  and
Lincoln J. Greenhill
Florian Niederhofer
Affiliation:
European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
Elizabeth Humphreys
Affiliation:
European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
Ciriaco Goddi
Affiliation:
European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
Lincoln J. Greenhill
Affiliation:
Harvard-Smithonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
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Abstract

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Radio Source I in the Orion BN/KL region provides the closest example of high mass star formation. It powers a rich ensemble of SiO and H2O masers, and is one of only three star-forming regions known to display SiO maser emission. Previous monitoring of different SiO masers with the VLBA and VLA has enabled the resolution of a compact disk and a protostellar wind at radii <100 AU from Source I, which collimates into a bipolar outflow at radii of 100-1000 AU (see contribution by Greenhill et al., this volume). Source I may provide the best case of disk-mediated accretion and outflow recollimation in massive star formation. Here, we report preliminary results of sub-arcsecond resolution 325 GHz H2O maser observations made with the SMA. We find that 325 GHz H2O masers trace a more collimated portion of the Source I outflow than masers at 22 GHz, but occur at similar radii suggesting similar excitation conditions. A velocity gradient perpendicular to the outflow axis, indicating rotation, supports magneto-centrifugal driving of the flow.

Keywords

ISM: individual (Orion KL) - ISM: jets and outflows - stars: formation - masers
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 8 , Symposium S287: Cosmic Masers - from OH to H0 , January 2012 , pp. 184 - 185
Copyright
Copyright © International Astronomical Union 2012

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