Abstract
We present the first submillimeter (865 μm) imaging spectral survey at 1'' resolution conducted with the Submillimeter Array toward Orion KL. Within the 2 × 2 GHz bandpasses (lower and upper sidebands, 337.2-339.2 and 347.2-349.2 GHz), we find about 145 spectral lines from 13 species, six isotopologues, and five vibrational excited states. Most nitrogen-bearing molecules are strong toward the hot core, whereas the oxygen-bearing molecules peak toward the southwest in the so-called compact ridge. Imaging of spectral lines is shown to be an additional tool to improve the identifications of molecular lines. Arcsecond spatial resolution allows us to distinguish the molecular emission of the sources I and n from that of the hot core. The only molecular species detected strongly toward source I is SiO, delineating mainly the collimated northeast-southwest low-velocity outflow. The two positions close to source I, which have previously been reported to show maser emission in the v = 0 28SiO (1-0) and (2-1) lines, show no detectable maser emission in the v = 0 28SiO (8-7) at our spatial resolution. SiO is weak toward source n, and thus source n may not currently be driving a molecular outflow. CH3OH is the molecule with the highest number of identified lines (46) in this spectral window. This line forest allows us to estimate temperatures in the region, and we find temperatures between 50 and 350 K, with the peak temperatures occurring toward the hot core. The detection of strong vibrational excited emission from the submillimeter continuum peak SMA1 supports the interpretation that the source SMA1 is likely of protostellar nature.
Highlights
Orion KL is the most studied region of massive star formation
The interferometric investigations found that the single-dish spectral features known as the ‘‘hot core,’’ ‘‘compact ridge,’’ and ‘‘plateau’’ are all associated with the KL region, while the dust continuum source CS1 about 2500 northeast of source I exhibits narrower line widths, lower temperatures, and only weak indications of star formation (e.g., Wright et al 1996)
The presented observations comprise a large set of molecular line data ($145 lines from $24 species, isotopologues, and vibrational excited states) taken simultaneously during only two observing nights
Summary
Orion KL is the most studied region of massive star formation. At a distance of $450 pc, its molecular spectral line emission is very strong (e.g., Schilke et al 1997a). The interferometric investigations found that the single-dish spectral features known as the ‘‘hot core,’’ ‘‘compact ridge,’’ and ‘‘plateau’’ are all associated with the KL region, while the dust continuum source CS1 about 2500 northeast of source I exhibits narrower line widths, lower temperatures, and only weak indications of star formation (e.g., Wright et al 1996). Uum peak between sources I and n is found, SMA1, which is either an independent, deeply embedded protostellar object or part of the more extended hot core These submillimeter continuum sources, reproduced, are used as a reference frame for the discussion of the line emission throughout this paper
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