Compatibility of the CO and HI linewidths considering the gas distributionand rotation curves

We have found the trend between CO and Hr linewidths by compiling the CO an d HI linewidths of 219 nearby galaxies, The trend is that the CO linewidths of fast rotating galaxies tend to be larger than the HI linewidths, and th at the Hr linewidths of slow rotating galaxies tend to be larger than the C O linewidths, whereas the intermediately rotating galaxies have almost equa l values. We have examined the trend using the synthetic rotation curve mod el given by Persic et al. (1996), which provides the linewidth - absolute m agnitude relations at any radii. We conclude that the trend is produced by the differences in CO and HI distributions in a galaxy and the gradient of a rotation curve that depends on the luminosity of the galaxy. We should no te that the distribution of the tracer of linewidths (e.g. CO, Hr) and the gradient of rotation curves influence observed linewidths, therefore the ex act linewidths should be corrected for them.