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CO Observations of M51

Published online by Cambridge University Press:  04 August 2017

G. Rydbeck
Affiliation:
Onsala Space Observatory S-439 00 Onsala, Sweden
G. Pilbratt
Affiliation:
Onsala Space Observatory S-439 00 Onsala, Sweden
Å. Hjalmarson
Affiliation:
Onsala Space Observatory S-439 00 Onsala, Sweden
H. Olofsson
Affiliation:
Onsala Space Observatory S-439 00 Onsala, Sweden
O. E. H. Rydbeck
Affiliation:
Onsala Space Observatory S-439 00 Onsala, Sweden

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We present observations, which are part of an ongoing investigation, of the CO (J=1–0) emission in the spiral galaxy M51. The spectra were obtained in a beamswitched on-on mode with the Onsala 20 m antenna (beam size ~33″), equipped with a cooled mixer and a 512 ×1 MHz multichannel receiver, and are shown in Figure 1. The inset diagram shows the observed positions superposed on the optical outline of the galaxy. With the present signal-to-noise ratio there is no evidence for an arm-interarm intensity contrast. This is even more apparent in integrated intensity. This result agrees with the lower resolution findings of Rickard et al. (1981). We have observed 13CO in one position (22″ south of the center). The 13CO to 12CO ratio, ∼0.1, agrees with Bell results from observations with a 1:7 beam (Encrenaz et al. 1979).

Type
I. Kinematics of Gas and the Underlying Mass Distribution
Copyright
Copyright © Reidel 1983 

References

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