SMA observations of the W3(OH) complex: Dynamical differentiation between W3(H2O) and W3(OH)

• Published in: Monthly notices of the Royal Astronomical Society 2016-03, Vol.456 (3), p.2681-2691
• Main Authors: Qin, Sheng-Li, Schilke, Peter, Wu, Jingwen, Liu, Tie, Wu, Yuefang, Sánchez-Monge, Álvaro, Liu, Ying
• Format: Article
• Language: English
• Subjects: Accretion disks; Kinematics; Star & galaxy formation
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stv2801

We present Submillimeter Array observations of the HCN (3–2) and HCO+ (3–2) molecular lines towards the W3(H2O) and W3(OH) star-forming complexes. Infall and outflow motions in the W3(H2O) have been characterized by observing HCN and HCO+ transitions. High-velocity blue/red-shifted emission, tracing the outflow, show multiple knots, which might originate in episodic and precessing outflows. ‘Blue-peaked’ line profiles indicate that gas is infalling on to the W3(H2O) dust core. The measured large mass accretion rate, 2.3 × 10−3 M⊙ yr−1, together with the small free-fall time-scale, 5 × 103 yr, suggest W3(H2O) is in an early evolutionary stage of the process of formation of high-mass stars. For the W3(OH), a two-layer model fit to the HCN and HCO+ spectral lines and Spizter/Infrared Array Camera (IRAC) images support that the W3(OH) H ii region is expanding and interacting with the ambient gas, with the shocked neutral gas being expanding with an expansion time-scale of 6.4 × 103 yr. The observations suggest different kinematical time-scales and dynamical states for the W3(H2O) and W3(OH).