Bispectrum speckle interferometry of the massive protostellar outflow source IRAS 23151+5912

We present bispectrum speckle interferometry of the massive protostellar object IRAS 23151+5912 in the near-infrared K? band. Our image shows the diffuse nebulosity north-east of two bright, point-like sources in unprecedented detail. By comparing our near-infrared image with mm continuum and CO molecular line radio maps we find that the brighter of the two point sources lies near the center of the mm peak, indicating that it is a massive protostar. The nebulosity coincides with the blueshifted molecular outflow component. The most prominent feature in the nebulosity is a bow-shock-like arc, pointing towards the bright point source. We suspect that this feature is associated with a precessing jet which has created an inward-pointed cone in the swept up material. We present numerical jet simulations that reproduce this and several other features observed in our speckle image of the nebulosity. Our data also reveal a narrow linear structure connecting the central point source to the extended diffuse nebulosity. This feature may represent the innermost parts of a jet that drives the strong molecular outflow from IRAS 23151+5912. With the aid of radiative transfer calculations we demonstrate that, in general, the observed inner structures of the circumstellar material surrounding high-mass stars are strongly influenced by the orientation and symmetry of the bipolar cavity, as well as the relative strength of shocked and reflected emission components.