PdBI sub-arcsecond study of the SiO microjet in HH212 - Origin and collimation of Class 0 jets - AstrophysicsReportar como inadecuado

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Abstract: The bipolar HH 212 outflow has been mapped in SiO using the extendedconfiguration of the Plateau de Bure Interferometer PdBI, revealing a highlycollimated SiO jet closely associated with the H2 jet component. We study atunprecedented resolution 0.34- across the jet axis the properties of theinnermost SiO ``microjet within 1000 AU of this young Class 0 source, tocompare it with atomic microjets from more evolved sources and to constrain itsorigin. The SiO channel maps are used to investigate the microjet collimationand velocity structure. A large velocity gradient analysis is applied to SiO2-1, 5-4 and 8-7 data from the PdBI and the Submillimeter Array toconstrain the SiO opacity and abundance. The HH212 Class 0 microjet showsstriking similarities in collimation and energetic budget with atomic microjetsfrom T Tauri sources. Furthermore, the SiO lines appear optically thick, unlikewhat is generally assumed. We infer Tkin ~ 50-500 K and an SiO-H2 abundancegreater than 4 10-8-6 10-5 for nH2 = 107-105 cm-3, i.e. 0.05-90% ofthe elemental silicon. This similar jet width, regardless of the presence of adense envelope, definitely rules out jet collimation by external pressure, andfavors a common MHD self-collimation and possibly acceleration process at allstages of star formation. We propose that the more abundant SiO in Class 0 jetscould mainly result from rapid less than 25 yrs molecular synthesis at highjet densities.

Autor: S. Cabrit, C. Codella, F. Gueth, B. Nisini, A. Gusdorf, C. Dougados, F. Bacciotti

Fuente: https://arxiv.org/

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