EDP Sciences
Free Access
Volume 431, Number 3, March I 2005
Page(s) 993 - 1005
Section Interstellar and circumstellar matter
DOI https://doi.org/10.1051/0004-6361:20041595
Published online 16 February 2005

A&A 431, 993-1005 (2005)
DOI: 10.1051/0004-6361:20041595

Subarcsecond mid-infrared and radio observations of the W3 IRS5 protocluster

F. F. S. van der Tak1, P. G. Tuthill2 and W. C. Danchi3

1  Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
    e-mail: vdtak@mpifr-bonn.mpg.de
2  School of Physics, University of Sydney, NSW 2006, Australia
3  NASA Goddard Space Flight Center, Infrared Astrophysics, Code 685, Greenbelt MD 20771, USA

(Received 5 July 2004 / Accepted 27 October 2004 )

Observations at mid-infrared (4.8-17.65  $\mu$m) and radio (0.7-1.3 cm) wavelengths are used to constrain the structure of the high-mass star-forming region W3 IRS5 on 0 $\farcs$1 (200 AU) scales. Two bright mid-infrared sources are detected, as well as diffuse emission. The bright sources have associated compact radio emission and probably are young high-mass stars. The measured sizes and estimated temperatures indicate that these sources together can supply the observed far-infrared luminosity. However, an optically thick radio source with a possible mid-infrared counterpart may also contribute significant luminosity; if so, it must be extremely deeply embedded. The infrared colour temperatures of 350-390 K and low radio brightness suggest gravitational confinement of the H II regions and ongoing accretion at a rate of a few 10 -8  $M_{\odot}$ yr -1 or more. Variations in the accretion rate would explain the observed radio variability. The low estimated foreground extinction suggests the existence of a cavity around the central stars, perhaps blown by stellar winds. At least three radio sources without mid-infrared counterparts appear to show proper motions of ~100 km s -1, and may be deeply embedded young runaway OB stars, but more likely are clumps in the ambient material which are shock-ionized by the OB star winds.

Key words: stars: circumstellar matter -- stars: formation -- instrumentation: high angular resolution -- ISM: individual objects: W3 IRS5

SIMBAD Objects

© ESO 2005

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