^(13)CH_3OH in OMC-1

Creators: Blake, Geoffrey A.; Sutton, E. C.; Masson, C. R.; Phillips, T. G.; Herbst, Eric; Plummer, Grant M.; De Lucia, Frank C.

Abstract

We report the identification of several previously unidentified or misidentified lines toward OMC-1 as components the J = 5 → 4 α-type band of ^(13)CH_30H, deduced by combining accurate laboratory spectroscopy with sensitive broad-band astronomical line searches. An LTE fit to the data yields a rotational temperature of T_(rot)~ 120 K and a ^(13)CH_30H column density of ~1.3 x 10^(15) cm^(-2), averaged over a 30" beam. A ^(12)C/^(13)C ratio of ~30 is derived. The assignment of the feature at 236063 MHz to the blended K = ±2 E transitions of ^(13)CH_30H, rather than to CO^+, removes a major discrepancy between observation and the predictions of ion-molecule chemical models of dense interstellar clouds.

Additional Information

© 1984 American Astronomical Society. Provided by the NASA Astrophysics Data System. Received 1984 April 3; accepted 1984 June 4. Single dish millimeter-wave astronomy at the Owens Valley Radio Observatory is supported by NSF grant AST 82-14693.The authors would also like to thank R. E. Miller of AT & T Bell Laboratories, Murray Hill, for supplying the SIS junctions used in this work. E. H., G. M. P., and F. C. D. L. acknowledge support from NASA via grant NAGW-189. E. H. also wishes to acknowledge the support of the NSF via grant AST 83-12270 for his theoretical program.

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