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Astron. Astrophys. 329, 243-248 (1998)

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The ionized wind of IRAS 08159-3543

Marcello Felli 1, Gregory B. Taylor 2, Th. Neckel 3 and H.J. Staude 3

1 Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy
2 NRAO, P.O. Box 0, Socorro, New Mexico 87801-0387, USA
3 Max-Plank-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany

Received 22 May 1997 / Accepted 14 July 1997

Abstract

We report the detection of cm radio emission from the ionized wind which had been suggested to exist in the inner part of the bipolar outflow around the embedded Young Stellar Object (YSO) IRAS 08159-3543. The small radio flux density, the spectral index and the unresolved size of the source are all consistent with an ionized stellar wind with a mass loss rate ( [FORMULA] 10-5 M [FORMULA] /yr), slightly smaller than that predicted from the observed H [FORMULA] radiation scattered in the neutral parts of the wind. This confirms that the fast flowing neutral material far out in the lobes must have been accelerated by the same mechanism at work near the luminous YSO.

The presence of an ionized wind implies the existence of a strong source of ionizing photons, which is much hotter than the star inferred from visible and NIR observations (and corresponding to a spectral type F - K). This could be an early spectral type star whose optical radiation is strongly attenuated by its surrounding disk. Alternatively, the ionizing radiation could be provided by the hot boundary layer of a highly active accretion disk surrounding a lower mass PMS star. This result is consistent with the notion, supported also by spectroscopic properties of the YSO, that the dominant source of optical and near IR radiation is a disk, whose color temperature depends on the spectral range within which it is determined.

IRAS 08159-3543, with its associated reflection nebula GN08.16.0, is one of the few cases where the inner ionized part of the wind and the outer neutral parts of a larger scale bipolar outflow can be observed simultaneously, and offers the opportunity to study the interaction of the wind with the surrounding disk in the first evolutionary stages of a YSO.

Key words: stars: formation – accretion, accretion disks – ISM: jets and outflows – H ii regions – ISM: individual objects: GN08.16.0, IRAS 08159-3543

Send offprint requests to: M. Felli (mfelli@arcetri.astro.it)

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© European Southern Observatory (ESO) 1998

Online publication: November 24, 1997
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