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Massive stars form whilst they are still embedded in dense envelopes. As aresult, the roles of rotation, mass loss and accretion in massive starformation are not well understood. This study evaluates the source of theQ-band, lambda=19.5 microns, emission of massive young stellar objects (MYSOs).This allows us to determine the relative importance of rotation and outflowactivity in shaping the circumstellar environments of MYSOs on 1000 AU scales.We obtained diffraction limited mid-infrared images of a sample of 20 MYSOsusing the VLT/VISIR and Subaru/COMICS instruments. For these 8 m classtelescopes and the sample selected, the diffraction limit, ~0.6", correspondsto approximately 1000 AU. We compare the images and the spectral energydistributions (SEDs) observed to a 2D, axis-symmetric dust radiative transfermodel that reproduces VLTI/MIDI observations of the MYSO W33A. We vary theinclination, mass infall rate, and outflow opening angle to simultaneouslyrecreate the behaviour of the sample of MYSOs in the spatial and spectraldomains. The mid-IR emission of 70 percent of the MYSOs is spatially resolved.In the majority of cases, the spatial extent of their emission and their SEDscan be reproduced by the W33A model featuring an in-falling, rotating dustyenvelope with outflow cavities. There is independent evidence that most of thesources which are not fit by the model are associated with ultracompact HIIregions and are thus more evolved. We find that, in general, the diverse 20micron morphology of MYSOs can be attributed to warm dust in the walls ofoutflow cavities seen at different inclinations. This implies that the warmdust in the outflow cavity walls dominates the Q-band emission of MYSOs. Inturn, this emphasises that outflows are an ubiquitous feature of massive starformation.

Probing the envelopes of massive young stellar objects with diffraction limited mid-infrared imaging