2005A&A...431..993V

Observations at mid-infrared (4.8-17.65µm) and radio (0.7-1.3cm) wavelengths are used to constrain the structure of the high-mass star-forming region W3 IRS5 on 0.1" (200AU) 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 350-390K and low radio brightness suggest gravitational confinement of the H II regions and ongoing accretion at a rate of a few 10^–8M_☉/yr 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 ∼100km/s, 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.