Global molecular gas properties of Seyfert galaxies - II. Analysis of the results

We use the data published in Paper I and Curran et al. (2000) to determine the global molecular gas luminosities and distributions in a sample of 22 Seyfert galaxies. From this we find definite differences in the CO to HCN luminosity ratios between the near-by and distant galaxies of the sample. This is perhaps due to a selection effect where we only observe the brightest of the distant sources. With regard to distributions, we find in the near-by (mapped) sample that the CO is usually much wider distributed than the central telescope beam and that the HCN is considerably more extended beyond the similar to1 kpc often cited in the literature. In fact this molecule has been detected as far as approximate to5 kpc from the centre of NGC 1365. We may also have detected a bar in HCN in NGC 5033. Also, using the data to complement the results of Curran (2000a), we find L-CO/L-FIR(Sy2) approximate to L-CO/L-FIR(Sy1) i.e. no difference in the molecular gas luminosities between the two main Seyfert classes. In fact we consider it more meaningful to discuss the differences between the near-by and distant sample (irrespective of Seyfert type), although both of these samples may show evidence that much of the far infrared luminosity could arise from an active galactic nucleus as opposed to being predominantly due to vigorous star formation. We do believe, however, that improved statistics would be of little value in distinguishing between these two scenarios and that future high resolution observations are the key to resolving this issue.