Astronomy and Astrophysics – Astrophysics
Scientific paper
Jul 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008a%26a...485..137c&link_type=abstract
Astronomy and Astrophysics, Volume 485, Issue 1, 2008, pp.137-152
Astronomy and Astrophysics
Astrophysics
17
Stars: Pre-Main-Sequence, Infrared: Ism, Ism: Jets And Outflows, Ism: Kinematics And Dynamics, Individual Objects: Iras 20126+4104
Scientific paper
Context: 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 IRAS 20126+4104 molecular jet, driven by a 10^4 L&sun; protostar, represents a suitable target to investigate. Aims: We present here an extensive analysis of this protostellar jet, deriving the kinematical, dynamical, and physical conditions of the H2 gas along the flow. Methods: The jet was investigated by means of near-IR H2 and [Fe II] narrow-band imaging, high-resolution spectroscopy of the 1-0 S(1) line (2.12 μm), NIR (0.9-2.5 μm) low-resolution spectroscopy, along with ISO-SWS and LWS spectra (from 2.4 to 200 μm). Results: 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 -14 km s-1 in the blue lobe, and from -8 to 47 km s-1 in the red lobe. The low-resolution spectra are rich in H2 emission, and relatively faint [Fe II] (NIR), [O I] and [C II] (FIR) emission is observed in the region close to the source. A warm H2 gas component has an average excitation temperature that ranges between 2000 K and 2500 K. Additionally, the ISO-SWS spectrum reveals a cold component (520 K) that strongly contributes to the radiative cooling of the flow and plays a major role in the dynamics of the flow. The estimated L_H2 of the jet is 8.2 ± 0.7 L&sun;, suggesting that IRAS 20126+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)˜ 7.5× 10-4 M&sun; yr-1). 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. Conclusions: As for a few other intermediate- and high-mass protostellar jets in the literature, we conclude that IRAS 20126+4104 jet is a scaled-up version of low-mass protostellar counterparts.
Based on observations collected at UKIRT, TNG, and at Subaru and ISO data archive.
Caratti Garatti Alessio o.
Eislöffel Jochen
Froebrich Dirk
Giannini Teresa
Nisini Brunella
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