AAS 203rd Meeting, January 2004
Session 94 Embedded Protostars
Poster, Wednesday, January 7, 2004, 9:20am-6:30pm, Hanover Hall

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[94.10] The Nature of the Massive Young Stars in W75 N

D. S. Shepherd (NRAO), S. E. Kurtz (Instituto de Astronomia, UNAM), L. Testi (INAF - Osservatorio Astrofisco di Arcetri)

We have observed the W75 N massive star forming region with OVRO in SiO(J=2-1 & J=1-0) at 3'' - 5'' resolution and with the VLA in 6 cm, 2 cm, and 7 mm continuum emission at 1.4'' - 0.2'' resolution. The abundance ratio of [SiO]/[H2] ~5-7x10-11 which is typical for what is expected in the ambient component of molecular clouds with active star formation. The SiO morphology is diffuse and centered on the positions of the ultracompact HII regions - no collimated, neutral jet was discovered. The ionized gas surrounding the protostars have emission measures ranging from 1-15x106 pc cm-6, densities from 0.4-5x104 cm-3, and derived spectral types of the central ionizing stars ranging from B0.5 to B2. Most of the detected sources have spectral indicies which suggest optically thin to moderately optically thick HII regions produced by a central ionizing star. The spread in ages between the oldest and youngest early-B protostars in the W75 N cluster = 0.1-5x106 years. This evolutionary timescale for W75 N is consistent with that found for early-B stars born in clusters forming more massive stars (Mstar > 25 Msun).

Owens Valley observations are supported by the NSF, NASA's Origins of Solar Systems program, and by the Norris Planetary Origins Project. VLA observations are supported by the NSF. UNAM support is provided by Project IN118401 and CONACyT Project E-36568.

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Bulletin of the American Astronomical Society, 35#5
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