AAS 203rd Meeting, January 2004
Session 71 Molecular Cloud Cores
Oral, Tuesday, January 6, 2004, 2:00-3:30pm, Regency VI

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[71.01] High-Resolution Line and Continuum Study of W3(H2O)

H. Chen (UC Berkeley), D.J. Wilner (Harvard-Smithsonian Center for Astrophysics), W.J. Welch (UC Berkeley)

We have carried out a high-resolution line and continuum study of a self-luminous hot core W3(H2O) (d=2.2 kpc) with the BIMA array. Our study suggests that W3(H2O) may harbor an embedded, accreting protobinary system, which is in the youngest phase known of massive star formation and in the course of developing an ultra-compact HII region. The continuum observations have resolved the hot core with beamsizes of 0.26" and 0.4" at 1.4 mm and 2.7 mm, respectively. The dust emission appeared double-peaked with a separation of 1.2" with peak positions at both 1.4 mm and 2.7 mm agreed remarkably well with the 8.4 GHz VLA observation (Wilner et. 1999). The 1.4 mm dust emission profiles can be explained by radially dependent power-law density distributions of indexes close to -1.5, suggesting the surrounding material is in a free-fall phase. The spectral indexes between 1.4 mm and 2.7 mm around the two peaks are close to 3.0, implying dust opacity power-law indexes of 1.0. We have also observed the K=2 to 6 components of the CH3CN (12-11) transitions at excitations of 69K to 326K above the ground with a beamsize of 1". By fitting all the K components simultaneously, we found a velocity difference of 2.0 km/s between the two continuum peaks, suggesting a minimum total mass of 12 M\odot. Since K=2, 3, and 6 components appeared optically thick, we have developeda radiative transfer model assuming population thermalized and found temperatures for the two sources about 80 K, which is much lower than the temperature of 200 K given by the rotation diagram from single-dish observations.

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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.