SMA Research: Submm line imaging of Orion-KL with the Submillimeter Array

We present the first submm (865 μm) imaging spectral line survey at one arcsecond resolution conducted with the Submillimeter Array toward Orion-KL. Within the two X two GHz bandpasses (lower and upper sidebands, 337.2-339.2GHz and 347.2-349.2GHz), we find about 145 spectral lines from 13 species, 6 isotopologues, and 5 vibrational excited states. Most nitrogen-bearing molecules are strong toward the hot core, whereas the oxygen-bearing molecules peak toward the south-west 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 line 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 north-east south-west 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) line 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 350K, with the peak temperatures occurring toward the hot core. The detection of strong vibrational excited line emission from the submm continuum peak SMA1 supports the interpretation that the source SMA1 is likely of protostellar nature.

Science Publication

  • H. Beuther, Q. Zhang, L .J. Greenhill, M. J. Reid, D. Wilner, E. Keto, H. Shinnaga, P. T. P. Ho, J. M. Moran, S.-Y. Liu ,and C.-M. Chang, Submm Line Imaging of Orion-KL at 865 um with the Submillimeter Array 2005, ApJ, 632, 355 (ADS | astro-ph/0506603)
  •   Orion-KL

    This image shows the first sub-arcsecond resolution submm continuum image ever observed. We clearly resolve the famous source I from the Orion hot core, and furthermore for the first time detect the infrared-source n also at submm wavelength. SMA1 is a separate emission feature but likely belongs to the larger-scale hot core. (Beuther et al. (2004))