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A search for ionized jets towards massive young stellar objects.

Purser, Simon and Lumsden, Stuart and Hoare, Melvin and Urquhart, James and Cunningham, Nichol and Purcell, Cormac and Brooks, Kate and Garay, Guido and Guzman, Andres and Voronkov, Maxim (2016) A search for ionized jets towards massive young stellar objects. University of Leeds. [Dataset]

Dataset description

Radio continuum observations using the Australia telescope compact array at 5.5, 9.0, 17.0 and 22.8 GHz have detected free-free emission associated with 45 of 49 massive young stellar objects and HII regions. Of these, 26 sources are classified as ionized jets (12 of which are candidates), 2 as ambiguous jets or disc winds, 1 as a disc-wind, 14 as HII regions and 2 were unable to be categorised. Classification as ionized jets is based upon morphology, radio flux and spectral index, in conjunction with previous observational results at other wavelengths. Radio-luminosity and momentum are found to scale with bolometric luminosity in the same way as low-mass jets, indicating a common mechanism for jet production across all masses. In 13 of the jets, we see associated non-thermal/optically-thin lobes resulting from shocks either internal to the jet and/or at working surfaces. Ten jets display non-thermal (synchrotron emission) spectra in their lobes, with an average spectral index of α = -0.55 consistent with Fermi acceleration in shocks. This shows that magnetic fields are present, in agreement with models of jet formation incorporating magnetic fields. Since the production of collimated radio jets is associated with accretion processes, the results presented in this paper support the picture of disc-mediated accretion for the formation of massive stars with an upper-limit on the jet phase lasting approximately 6.5×10⁴ yr. Typical mass loss rates in the jet are found to be 1.4 × 10⁻⁵ M☉ yr⁻¹ with associated momentum rates of the order 1-2 × 10⁻² M☉ km s⁻¹ yr⁻¹.

Keywords: stars: formation, stars: massive, stars: protostars, ISM: jets and outflows, radio continuum: ISM, surveys
Subjects: F000 - Physical sciences > F500 - Astronomy > F510 - Astrophysics
Divisions: Faculty of Mathematics and Physical Sciences > School of Physics and Astronomy
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License: Creative Commons Attribution 4.0 International (CC BY 4.0)
Date deposited: 10 Jun 2016 14:30




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