A Spectral Line Survey from 138.3 to 150.7 GHZ toward Orion-KL

Abstract

We present the results of a spectral line survey from 138.3 to 150.7 GHz toward Orion-KL. The observations were made using the 14 m radio telescope of Taeduk Radio Astronomy Observatory. Typical system temperatures were between 500 and 700 K, with the sensitivity between $0.02-0.06$ K in units of ${\mathrm{T}}_{\mathrm{A}}^{\ast }$. A total of 149 line spectra are detected in this survey. Fifty lines have been previously reported, however we find 99 new detections. Among these new lines, 32 are `unidentified', while 67 are from molecular transitions with known identifications. There is no detection of H or He recombination lines. The identified spectra are from a total of 16 molecular species and their isotopic variants. In the range from 138.3 to 150.7 GHz, the strongest spectral line is the J=3-2 transition of CS molecule, followed by transitions of the ${\mathrm{H}}_2\mathrm{CO}$, $\mathrm{C}{\mathrm{H}}_3\mathrm{OH}$, $\mathrm{C}{\mathrm{H}}_3\mathrm{CN}$, and $\mathrm{S}{\mathrm{O}}_2$. Spectral lines from the large organic molecules such as $\mathrm{C}{\mathrm{H}}_3\mathrm{OH}$, $\mathrm{C}{\mathrm{H}}_3\mathrm{OC}{\mathrm{H}}_3$, $\mathrm{HCOOC}{\mathrm{H}}_3$, ${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{CN}$ and $\mathrm{C}{\mathrm{H}}_3\mathrm{CN}$ are prominent; with 80 % of the identified lines arising from transitions of these molecules. The rotational temperatures and column densities are derived using the standard rotation diagram analysis for $\mathrm{C}{\mathrm{H}}_3\mathrm{OH}$ (${}^{13}\mathrm{C}{\mathrm{H}}_3\mathrm{OH}$), $\mathrm{HCOOC}{\mathrm{H}}_3$, $\mathrm{C}{\mathrm{H}}_3\mathrm{CN}$ and $\mathrm{S}{\mathrm{O}}_2$ with $10\sim 270K$ and $0.2\sim 20\times 10^{15}\mathrm{c}{\mathrm{m}}^{-2}$. These estimates are fairly comparable to the values for the same molecule in other frequency regions by other studies.

arXiv comment10 figures, 2 tex files for a manuscript and tables, accepted to ApJ

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