The distribution of molecules in the core of OMC-1

Abstract

We have surveyed molecular line emission from five positions near the core of the Orion molecular cloud OMC-1, in the vicinity of Orion-KL, with 14 sec spatial resolution. The frequency coverage of the survey was from 334 to 343 GHz. A maximum entropy analysis has been used to deconvolve the double-sideband data into single-sideband spectra for each position. The rms noise levels in the single-sideband spectra are of order 0.2 K at 1 MHz resolution. A total of 291 resolvable lines have been detected, corresponding to 26 different chemical species. There are 17 currently unidentified lines clearly present in at least one position with peak T*<SUB>R</SUB> greater than 1 K. Some of these may be due to known molecular species whose spectra have not been completely determined. An excitation analysis indicates that kinetic temperatures in these regions are in a range of approximately 60-200 K with densities of 3 x 10<SUP>5</SUP>/cu cm to 3 x 10<SUP>6</SUP>/cu cm. Some highly reactive species, including free radicals, have peak column densities to the northeast of the Orion core in the direction of the Orion 'extended ridge.' Most other species have maximum column densities about 8 sec to southwest of IRc2, in the direction of the Orion 'compact ridge.' Kinematic characteristics are quite variable, with velocity dispersions ranging from 1.5 to 40 km/s.