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R. Y. Shuping, M. Morris (Div. of Astronomy & Astrophysics, UCLA), J. Bally (Center for Astrophysics & Space Astronomy, CU Boulder)
We present a new mid-infrared (12 \mum) map of the BN/KL high-mass star-forming complex in Orion using the LWS instrument at Keck I. Despite poor weather we achieved nearly diffraction-limited images (FWHM = 0.38'') over a roughly 25''\times25'' region centered on IRc2 down to a flux limit of 250 mJy. Many of the known infrared (IR) sources in the region break up into smaller sub-sources. We have also detected 6 new mid-IR sources. Nearly all of the sources are resolved in our mosaic. The near-IR source ``n'' is slightly elongated along a NW--SE position angle in the mid-IR, and perfectly bisects the double-peaked radio source ``L''. Source n has been identified as a candidate for powering the massive IR luminosity of the BN/KL region (L = 105 Lsun). We postulate that the 12 \mum emission arises in a circumstellar disk surrounding a young high-mass star. The morphology of the mid-IR emission, Orion ``hot core'' (as seen in NH3 emission), and the location of water and OH masers is very suggestive of a bipolar cavity centered on source n and perpendicular to the long axis of the hypothetical circumstellar disk. The new disk orientations for high-mass candidate sources ``I'' (Greenhill et al. 2003) and n coincide roughly with the OMC1 ``low-velocity'' outflow (NE--SW). This leaves no known source for the ``high-velocity'' CO outflow and H2 fingers emanating from OMC1 and aligned roughly NW--SE: either the outflow axes have changed, or there is an additional as yet undetected source in the region. IRc2, once thought to be the dominant energy source for the BN/KL region, clearly breaks into 4 sub-sources in our mosaic, as seen previously at 4 \mum. The anti-correlation of mid-IR emission and NH3 emission from the nearby hot core indicates that the IRc2 sources are roughly coincident (or behind) the dense hot core. We suggest that the IRc2 sources are in fact lower-mass YSOs surrounding the young high-mass star powering compact radio source I embedded within the hot core; similar to the low-mass YSOs (``proplyds'') surrounding the Trapezium stars in the Orion Nebula. We also discuss a new arc-like feature SW of the BN object, and some curious morphology surrounding near-IR source ``t".
This research has been supported by a cooperative agreement through the Universities Space Research Association (USRA) under grant # 85502-02-02 to M. Morris.
The author(s) of this abstract have provided an email address for comments about the abstract: shuping@astro.ucla.edu
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.