ORIGIN OF THE MIDINFRARED EMISSION AND SUPERSONIC JET TOWARD LKH-ALPHA-234

We present high-resolution imaging of the region around the Herbig Ae/ Be star LkH alpha 234 in the 10 mu m and 17 mu m atmospheric windows a nd in the H-2 v=1-0 S(1) line and adjacent continuum. LkH alpha 234 is unresolved at mid-infrared wave lengths (FWHM < 1.3 '') and has a dec reasing spectrum compatible with an accretion disk. A cold mid-infrare d companion is revealed 2.7 '' to the north-west of the optical star, corresponding well to the polarization centre identified in the K-band by Weintraub et al. (1994). The companion illuminates an are-shaped r eflection nebula with very red colours, and is associated with a radio continuum source, H2O masers, and a bright extended H-2 emission knot , indicating that it is deeply embedded and has strong outflow activit y. However, its role in driving the optical jet near LkH alpha 234 is not clear. Our high-resolution H-2 image reveals that the jet has a co mplex structure, with an inner part at PA 226 degrees emitting brightl y in H-2, and an outer part at PA 252 degrees seen only in [SII]. The inner H-2 jet does not point back exactly toward the infrared companio n, indicating either that it is deflected after leaving that object, o r that it is driven by a yet unidentified source. Available long-slit spectra favor the idea that the outer jet emitting in [SII] could be p owered by the 10 mu m companion rather than by LkH alpha 234. High-res olution [SII] imaging is required to test this hypothesis.