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Astron. Astrophys. 347, 634-639 (1999)

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Extended warm CO gas in three nearby galaxies *

R. Wielebinski 1, M. Dumke 2 and Ch. Nieten 1

1 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany
2 Institut de Radioastronomie Millimétrique, 300, rue de la Piscine, F-38406 St. Martin d'Hères, France

Received 15 December 1998 / Accepted 10 March 1999


We report the detection of distributed CO(3-2) line emission in nearby normal galaxies. The CO gas is a well-known tracer of physical conditions in the emitting regions. The line transitions from higher energy levels (the J=3 level is 33 K above ground) are indicators of the presence of warm and dense gas. Until now this warm gas has been studied only in the nuclei of starburst galaxies. Using the Heinrich Hertz Telescope on Mt. Graham we were able to detect extended CO(3-2) line emission in more than ten normal galaxies. In this paper we present the results for the three galaxies M51, NGC 278 and NGC 4631. In particular, we compare our results with observations of the lower CO line transitions made with radio telescopes of similar angular resolution.

Key words: line: profiles – molecular data – ISM: molecules – galaxies: individual: M 51, NGC 278, NGC 4631 – galaxies: ISM

* Based on observations with the Heinrich-Hertz-Telescope (HHT). The HHT is operated by the Submillimeter Telescope Observatory on behalf of Steward Observatory and the MPI für Radioastronomie.

Send offprint requests to: R. Wielebinski (rwielebinski@mpifr-bonn.mpg.de)

© European Southern Observatory (ESO) 1999

Online publication: June 30, 1999