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K. R. Covey (University of Washington), T. P. Greene (NASA Ames Research Center), G. W. Doppmann (NASA Ames Research Center / Gemini Science Center), C. J. Lada (CfA Harvard)
High resolution, high signal-to-noise observations of K band spectral features (Al, Mg, Na, CO) in 41 Class I/flat spectrum low mass protostars allow us to measure the radial velocities (Vlsr) and rotational velocities (vsini) characteristic of low mass, actively accreting protostars. We compare the resultant rotational velocity distribution of our sample to that of more evolved classes of pre-main sequence stars, finding that Class I/flat spectrum objects are rotating on average a factor of 2 faster, in median projected rotational velocity, than Class II objects. This suggests that Class I sources must lose half or more of their angular momentum content before evolving to the classical T Tauri phase. However, much ( > 99%) of the angular momentum loss required to turn dense molecular cores into classical T Tauri stars has already occurred by the Class I/flat spectrum phase.
Additionally, radial velocity analysis indicates no significant difference within observational limits (± 2 km/sec) between either the central velocity or the dispersion of protostellar radial velocities and that of the local CO gas. This finding suggests that, on the whole, protostellar populations are likely still gravitationally bound to the clouds in which they are being formed. Some objects ( ~12%) do show significant radial velocity offsets from their local gas, which may be due to close companions or perhaps ejection events.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.