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Astron. Astrophys. 345, L5-L8 (1999)

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Letter to the Editor

Cross-calibrated VLA observations of H2O maser and 1.3 cm continuum emission in IRAS 18162-2048 (= HH 80-81 IRS)

Josep Martí 1, Luis F. Rodríguez 2 and José M. Torrelles 3

1 Departamento de Física, Escuela Politécnica Superior, Universidad de Jaén, Calle Virgen de la Cabeza, 2, E-23071 Jaén, Spain
2 Instituto de Astronomía, UNAM, Apdo. Postal 70-264, México, DF 04510, México
3 Institut d'Estudis Espacials de Catalunya (IEEC/CSIC), Edifici Nexus, C/ Gran Capità 2-4, E-08034 Barcelona, Spain
and Instituto de Astrofísica de Andalucía, CSIC, Spain

Received 10 March 1999 / Accepted 29 March 1999

Abstract

We report simultaneous continuum (1.3 cm) and H2O maser line observations, made with the Very Large Array (A configuration), toward IRAS 18162-2048, the luminous exciting source of the HH 80-81 complex. The continuum observations, cross-calibrated with the H2O maser emission, provide information of the thermal jet of this young massive star with unprecedented angular resolution and fidelity. We find that the jet is already collimated on scales smaller than 100 AU. The analysis of the new 1.3 cm data and of previously obtained 3.6 cm data show that the source has the frequency dependences in major axis and flux density that characterize biconical jets. In particular, we find [FORMULA] and [FORMULA]. An improved determination of the mass loss rate in ionized gas, [FORMULA] yr-1, is provided with these new observations.

As it was known from previous studies, the H2O maser emission does not coincide with the thermal jet but with a faint source of radio continuum emission displaced by [FORMULA]7" to the northeast of the thermal jet. The H2O masers appear in two compact clusters separated by [FORMULA]20 mas. One of the clusters is formed by spots in a linear geometry. The kinematics of these maser spots and their large blueshift with respect to the radial velocity of the parental molecular cloud suggest that they trace material accelerated by outflow phenomena, instead of a possible disk.

Key words: stars: individual: IRAS 18162-2048 – stars: individual: HH 80-81 IRS – stars: formation – ISM: Herbig-Haro objects – ISM: jets and outflows

Send offprint requests to: J. Martí, jmarti@ujaen.es

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© European Southern Observatory (ESO) 1999

Online publication: April 12, 1999
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