CO J = 10 observations of the Circinus galaxy using the Mopra 22-m radio-telescope

Conclusion

Using the facilities at Mopra, we have successfully detected CO (1-0) at 5 different positions in the Circinus galaxy. Our conclusions based on these initial results are as follows:

(a) The nuclear CO distribution has a profile with a FWHM of 550 pc. The peak emission occurs within 20 of the radio continuum nucleus.

(b) The velocity components at the centre of the galaxy are distributed in a 445 kms range, indicating rapid rotation of the molecular gas at the centre of the galaxy.

(c) The molecular mass of the Circinus galaxy is at least 7.5 4.1 10 M.

(d) The star forming efficiency of the galaxy is 16 9 LM .

These results are consistent with a galaxy undergoing an aggressive stage of nuclear star formation. More data with better resolution and sensitivity are needed to map the molecular gas in the outer regions of the Circinus galaxy and to obtain an understanding of how the gas and the spiral structure are related in this active galaxy. Also, high resolution , high sensitivity FIR data are needed to correctly determine which regions in the galaxy are responsible for star formations. This question is particularly interesting for the Circinus galaxy given its unusual radio continuum morphology and strong radio/infra-red nucleus.

© Copyright Astronomical Society of Australia 1997