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2008A&A...485..137C - Astronomy and Astrophysics, volume 485, 137-152 (2008/7-1)

Molecular jets driven by high-mass protostars: a detailed study of the IRAS20126+4104 jet.


Abstract (from CDS):

Protostellar jets from intermediate- and high-mass protostars provide an excellent opportunity to understand the mechanisms responsible for intermediate- and high-mass star-formation. A crucial question is if they are scaled-up versions of their low-mass counterparts. Such high-mass jets are relatively rare and, usually, they are distant and highly embedded in their parental clouds. The IRAS20126+4104 molecular jet, driven by a 104L protostar, represents a suitable target to investigate. We present here an extensive analysis of this protostellar jet, deriving the kinematical, dynamical, and physical conditions of the H2 gas along the flow. The jet was investigated by means of near-IR H2 and [FeII] narrow-band imaging, high-resolution spectroscopy of the 1-0S(1) line (2.12µm), NIR (0.9-2.5µm) low-resolution spectroscopy, along with ISO-SWS and LWS spectra (from 2.4 to 200µm). The flow shows a complex morphology. In addition to the large-scale jet precession presented in previous studies, we detect a small-scale wiggling close to the source, which may indicate the presence of a multiple system. The peak radial velocities of the H2 knots range from -42 to -14km/s in the blue lobe, and from -8 to 47km/s in the red lobe. The low-resolution spectra are rich in H2 emission, and relatively faint [FeII] (NIR), [OI] and [CII] (FIR) emission is observed in the region close to the source. A warm H2 gas component has an average excitation temperature that ranges between 2000K and 2500K. Additionally, the ISO-SWS spectrum reveals a cold component (520K) that strongly contributes to the radiative cooling of the flow and plays a major role in the dynamics of the flow. The estimated LH2 of the jet is 8.2±0.7L, suggesting that IRAS20126+4104 has a significantly increased accretion rate compared to low-mass YSOs. This is also supported by the derived mass flux rate from the H2 lines ({dot}(M)out(H2)∼7.5x10–4M/yr). The comparison between the H2 and the outflow parameters strongly indicates that the jet is driving the outflow, at least partially. As already found for low-mass protostellar jets, the measured H2 outflow luminosity is tightly related to the source bolometric luminosity. As for a few other intermediate- and high-mass protostellar jets in the literature, we conclude that IRAS20126+4104 jet is a scaled-up version of low-mass protostellar counterparts.

Abstract Copyright:

Journal keyword(s): stars: pre-main-sequence - infrared: ISM - ISM: jets and outflows - ISM: kinematics and dynamics - individual objects: IRAS20126+4104

Simbad objects: 16

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