Issue A&A Volume 493, Number 2, January II 2009 Page(s) 547 - 556 Section Interstellar and circumstellar matter DOI http://dx.doi.org/10.1051/0004-6361:200810598 Published online 30 October 2008

A&A 493, 547-556 (2009)
DOI: 10.1051/0004-6361:200810598

A multi-wavelength study of a double intermediate-mass protostar – from large-scale structure to collimated jets

J. Forbrich^{1, 2, 3}, Th. Stanke^{4, 5}, R. Klein^{6, 7}, Th. Henning⁸, K. M. Menten¹, K. Schreyer², and B. Posselt<sup>2, 3, 6

1</sup>  Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
²  Astrophysikalisches Institut und Universitäts-Sternwarte Jena, Schillergäßchen 2-3, 07745 Jena, Germany
³  Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 72, Cambridge, MA 02138, USA
    e-mail: jforbrich@cfa.harvard.edu
⁴  Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
⁵  European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
⁶  Max-Planck-Institut für extraterrestrische Physik, Giessenbachstr. 1, 85748 Garching bei München, Germany
⁷  Department of Physics, University of California, Berkeley, CA 94720, USA
⁸  Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany

Received 14 July 2008 / Accepted 25 September 2008

Abstract
Aims. The earliest stages of intermediate- and high-mass star formation remain poorly understood. To gain deeper insights, we study a previously discovered protostellar source that is deeply embedded and drives an energetic molecular outflow.
Methods. The source, UYSO 1, located close to IRAS 07029–1215 at a distance of about 1 kpc, was observed in the (sub)millimeter and centimeter wavelength ranges, as well as at near-, mid-, and far-infrared wavelengths.
Results. The multi-wavelength observations resulted in the detection of a double intermediate-mass protostar at the location of UYSO 1. In addition to the associated molecular outflow, with a projected size of 0.25 pc, two intersecting near-infrared jets with projected sizes of 0.4 pc and 0.2 pc were found. However, no infrared counterparts to the driving sources could be detected in sensitive near- to far-infrared observations (including Spitzer). In interferometric millimeter observations, UYSO 1 was resolved into two continuum sources with high column densities (>10²⁴ cm^-2) and gas masses of 3.5  and 1.2 , with a linear separation of 4200 AU. We report the discovery of a H₂O maser towards one of the two sources. Within an appropriate multi-wavelength coverage, the total luminosity is roughly estimated to be 50 , shared by the two components, one of which is driving the molecular outflow that has a dynamical timescale of less than a few thousand years. The jets of the two individual components are not aligned. Submillimeter observations show that the region lacks the typical hot-core chemistry.
Conclusions. We find two protostellar objects, whose associated circumstellar and parent core masses are high enough to suggest that they may evolve into intermediate-mass stars. This is corroborated by their association with a very massive and energetic CO outflow, suggesting high protostellar accretion rates. The short dynamical timescale of the outflow, the pristine chemical composition of the cloud core and absence of hot core tracers, the absence of detectable radio continuum emission, and the very low protostellar luminosity argue for an extremely early evolutionary stage.

Key words: stars: formation -- ISM: jets and outflows

© ESO 2009

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