Volume 431, Number 3, March I 2005
|Page(s)||993 - 1005|
|Section||Interstellar and circumstellar matter|
|Published online||16 February 2005|
Subarcsecond mid-infrared and radio observations of the W3 IRS5 protocluster
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany e-mail: email@example.com
2 School of Physics, University of Sydney, NSW 2006, Australia
3 NASA Goddard Space Flight Center, Infrared Astrophysics, Code 685, Greenbelt MD 20771, USA
Accepted: 27 October 2004
Observations at mid-infrared (4.8–17.65 μm) and radio (0.7–1.3 cm) wavelengths are used to constrain the structure of the high-mass star-forming region W3 IRS5 on 01 (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 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
© ESO, 2005
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