VLBI Mapping of 43 GHz SiO Emission Associated with IRc2 in Orion-KL

Abstract

Information on the structure of the molecular flow within 1″ of IRC-2, in Orion-KL, is sparse. Measurements of the continuum at 7.8μ and 12.5μ show a disk of size and suggest that the center of the disk may be dust free (Lester et al. 1985). Aperture synthesis mapping of water maser shell features (Sylber 1986) has provided information on the scale. Smaller scales can be studied by mapping SiO maser emission. We observed the 43 GHz, v=1, J = 1 → 0, transition of SiO using a 2 station interferometer with a 74 km baseline between Haystack Observatory, Westford, MA and Five College Radio Observatory, New Salem, MA. The fringe spacing was 20 milliarcseconds (mas) and the velocity resolution was 0.25 km-s −1 . Our results provide the highest resolution view to date of what is likely to be the inner of IRC-2.