Distribution of carbon monoxide in three face-on galaxies

The data were obtained between 1975 and 1981. The observed positions are arranged in hexagonal grids, spaced by 1 arcmin (roughly equivalent to the full half-power beamwidth). The initial analysis is based solely on maps of the integrated intensity under the line profile. The CO emission is seen to be confined to the bright optical disks. A sufficient number of points have been measured off the disks to verify that there is a pronounced drop off at the optical 'edges'. By comparison, the extent of the HI distributions for these galaxies is significantly larger. If the data are averaged in radial bins, the result involves essentially monotonic declines in the CO flux, dropping from the strong central enhancements to about 25 percent of the peak flux in a disk that is seen to have fairly constant flux over an extent of approximately 10 kpc. The decline from the peak is found to be the same for all three when viewed in angular distance, indicating that the central sources are unresolved