Origin of the mid - infrared emission and supersonic jet toward LkH α 234 ?

We present high-resolution imaging of the region around the Herbig Ae/Be star LkHα 234 in the 10μm and 17μm atmospheric windows and in the H2 v=1-0 S(1) line and adjacent continuum. LkHα 234 is unresolved at mid-infrared wavelengths (FWHM < 1.3′′) and has a decreasing spectrum compatiblewith an accretion disk.A coldmid-infrared companion is revealed 2.7′′ to the north-west of the optical star, corresponding well to the polarization centre identified in the K-band byWeintraub et al. (1994). The companion illuminates an arc-shaped reflection nebula with very red colours, and is associated with a radio continuum source, H2O masers, and a bright extended H2 emission knot, indicating that it is deeply embedded and has strong outflow activity. However, its role in driving the optical jet near LkHα 234 is not clear. Our high-resolutionH2 image reveals that the jet has a complex structure, with an inner part at PA 226◦ emitting brightly in H2, and an outer part at PA 252◦ seen only in [Sii]. The innerH2 jet does not point back exactly toward the infrared companion, indicating either that it is deflected after leaving that object, or 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 powered by the 10μm companion rather than by LkHα 234. High-resolution [Sii] imaging is required to test this hypothesis.