3.1. Morphology in the K-band image
In Fig. 1 we present our reconstructed K-band images of S140 IRS1. Our images show a wealth of previously unseen details. The central source IRS1 has a point-like appearance. A series of diffraction rings are clearly visible around IRS1. While the first ring is perfectly closed, the following diffraction rings are broken. A detailed investigation of the data indicates that the central source is marginally resolved with a FWHM Gaussian diameter of approximately 20 mas (corresponding to a physical size of AU at the assumed distance of 900 pc) and is probably elongated in a north-south direction.
Our images show a bright extended feature of diffuse emission pointing from IRS1 towards the south-east. This emission has a very clumpy structure with several prominent knots as indicated in our contour image. Clump A is located on the axis defined by the general shape of the emission structure. Three other clumps, denoted as B, C, and D, can be seen to the right or left of the axis. Additionally, a rather extended feature of emission, denoted as G, is seen south-east of IRS1. Nevertheless, the general shape of the diffuse emission follows a well defined direction. The line connecting the central maximum with clump A has a position angle of (measured counter-clock wise from north). The two features denoted as E and F seem to trace a structure that is oriented roughly perpendicular to the outflow direction.
3.2. Polarization maps
Our polarization maps show that the light from the elongated feature is strongly polarized, with degrees of polarization ranging up to 50%. Our two polarization maps, which were taken in slightly different filters (see above), agree very well. If we draw lines perpendicular to each polarization vector in our maps, nearly all these lines cross within less than of the central intensity peak. Thus, our maps are very consistent with a centro-symmetric polarization pattern around the central source. Comparison of our polarization maps with theoretical simulated polarization maps (e.g. Fischer et al. 1996) suggests that the light from the elongated feature is scattered light, originating from the central source.
© European Southern Observatory (ESO) 2000
Online publication: October 2, 2000