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Astron. Astrophys. 360, 663-670 (2000)

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Tracing the root of the bipolar jet in IRAS 20126+4104: VLBA observations of H2O masers *

L. Moscadelli 1, R. Cesaroni 2 and M.J. Rioja 3

1 Stazione Astronomica di Cagliari, Loc. Poggio dei Pini, strada 54, 09012 Capoterra (Cagliari), Italy
2 Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
3 Observatorio Astronomico Nacional (IGN), Apartado 1143, 28800 Alcalá de Henares (Madrid), Spain

Received 21 December 1999 / Accepted 26 April 2000


We present VLBA observations of the H2O masers towards IRAS 20126+4104, a high-mass young stellar object which is believed to be associated with a rotating disk and a bipolar outflow/jet system collimated along the disk axis. A model fit to the positions and velocities of the maser spots demonstrates that these could arise on a conical surface at the interface between the jet and the surrounding molecular gas. The masers expand from a common centre which coincides, within the uncertainties, with the position of the embedded young stellar object: the expansion velocity is less than that measured on a much larger scale in the SiO(2-1) line and this indicates that the jet is sensitively braked close to its origin by the interaction with the surrounding medium.

Key words: masers – ISM: individual objects: IRAS 20126+4104 – ISM: jets and outflows – radio lines: ISM

* Based on observations carried out with the Very Large Baseline Array. The VLBA is a facility of the NRAO, which is operated by Associated Universities, Inc., under contract with the NSF.

Send offprint requests to: L. Moscadelli (mosca@ca.astro.it)

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© European Southern Observatory (ESO) 2000

Online publication: August 17, 2000