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Molecular excitation in Centaurus A: the CO J=1-0 map and CO line ratios *
W. Wild 1, 2,
A. Eckart 3 and
T. Wiklind 4
Received 27 September 1996 / Accepted 3 December 1996
We present a fully sampled map of the 13 CO J=1-0 emission in the dust lane of Centaurus A as well as 13 CO 2-1 and for the first time C18 O 1-0 spectra at selected positions. The morphology of the 13 CO map is similar to the 12 CO 1-0 and 2-1 maps. Maps of the 12 CO 2-1/1-0 and 12 CO/13 CO 1-0 ratios show small variations of the ratios throughout the disk with a rise of the 12 CO 2-1/1-0 ratio towards the southeast. The values found are within the range as found in other galaxies. Radiative transfer calculations indicate a kinetic temperature of 10-15 K and H2 densities on the order of cm-3. In the southeastern part of the dust lane, the gas appears to be warmer (20-30 K) which may be due to a greater star formation activity. The total molecular mass is about .
The observed 12 CO 2-1 intensity is consistent with the molecular gas being distributed in a thin, warped disk as modelled by Quillen et al. (1992). Comparison of the measurements with the kinematic model shows good agreement.
Key words: galaxies: individual: NGC 5128 galaxies: nuclei galaxies: ISM radio lines: galaxies
Send offprint requests to: W. Wild, email@example.com
© European Southern Observatory (ESO) 1997
Online publication: June 5, 1998