In Fig. 1, we show the spectra obtained toward 29 external galaxies. For the presentation, the resolution of the spectrometer has been degraded to 6.7 km s-1, only for IC 10 it is 3.8 km s-1. We have detected line emission toward all sources. For most of these sources, this is the first time that data are published. Even for Centaurus A, which at Mount Graham never rises higher than , a high quality baseline and repeatable line profiles and line intensities were obtained. From the data, we have determined the line flux, , and we have estimated the line width and the radial velocity using either Gaussian fits to the lines, or, in the case of non-Gaussian lineshapes, giving the first or second moments of the spectra. Results as well as intensities of the 1-0 and 2-1 lines, which were observed by us or taken from published 30-m data, are given in Table 1. In Table 2, we summarize important source parameters together with the flux ratio of the 12CO 3-2 and 1-0 lines.
Table 1. Line parameters of detected
Table 2. Properties of the observed galaxies
In general, there is good agreement between shapes and intensities of our observed lines and other data (see the Appendix). Data taken in April 1998 at our positions with the same setup (R. Wielebinski, pers. comm.) show virtually identical calibration scales for M 82, M 83, IC 342, NGC 2146, NGC 3351 and NGC 5907. For NGC 3627, NGC 3628 and M 51 these data show a 30% higher intensity, and for NGC 3079 a 30% lower intensity. Such differences are compatible with our estimate of the calibration errors and with the uncertainties from the fits to the line profiles.
Our literature search made clear that the application of correct calibration schemes cannot be taken for granted in all cases. In order to present a sample that is as homogeneous as possible, we therefore restrict our comparison to CO 1-0 and 2-1 data which have been measured using the IRAM 30-m telescope. In Fig. 2 we show the velocity integrated relative intensities of the three lowest CO transitions, normalized to the CO 1-0 transition.
© European Southern Observatory (ESO) 1999
Online publication: November 26, 1998