A New Mid-Infrared Map of the BN/KL Region Using the Keck Telescope

We present a new mid-infrared (12.5micron) map of the BN/KL high-massstar-forming complex in Orion using the LWS instrument at Keck I. Despite poorweather we achieved nearly diffraction-limited images (FWHM = 0.38'') over aroughly 25'' X 25'' 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 smallersub-components. We have also detected 6 new mid-IR sources. Nearly all of thesources are resolved in our mosaic. The near-IR source ''n'' is slightlyelongated in the mid-IR along a NW--SE axis and perfectly bisects thedouble-peaked radio source ''L''. Source n has been identified as a candidatefor powering the large IR luminosity of the BN/KL region (L = 10^5 L_sun). Wepostulate that the 12 micron emission arises in a circumstellar disksurrounding source n. The morphology of the mid-IR emission and the Orion ''hotcore'' (as seen in NH_3 emission), along with the location of water and OHmasers, is very suggestive of a bipolar cavity centered on source n and alignedwith the rotation axis of the hypothetical circumstellar disk. IRc2, oncethought to be the dominant energy source for the BN/KL region, clearly breaksinto 4 sub-sources in our mosaic, as seen previously at 3.8 -- 5.0 micron. Theanti-correlation of mid-IR emission and NH_3 emission from the nearby hot coreindicates that the IRc2 sources are roughly coincident (or behind) the densehot core. The nature of IRc2 is not clear: neither self-luminous sources(embedded protostars) nor external heating by source I can be definitivelyruled out. We also report the discovery of a new arc-like feature SW of the BNobject, and some curious morphology surrounding near-IR source ''t".Comment: To appear in The Astronomical Journal, July 2004 (16 pages, 7 figures