CO Survey of a Distance-limited Seyfert Sample. I. The Data

We present the data of 12CO (J = 1–0) observations of the central regions of a sample of 43 nearby Seyfert galaxies (cz ≤ 5000 km s-1) with the NRO 45 m telescope. The general properties of this sample are also discussed, but a more detailed analysis is deferred to Paper II. The CO detection rate of this sample (i.e., almost 50%) is comparable to that of other spiral galaxy surveys in similar redshift ranges made with that telescope. There seems to be no difference in the detection rates of Seyfert galaxies types 1 and 2. Since we observed a single point centered at the nucleus, and the average ratio of the beam HPBW of the 45 m telescope to the apparent optical diameter of these objects was 0.13, only a small fraction of the total molecular gas is recovered. However, a clear correlation of the CO contents with the IRAS FIR luminosities is also seen, and there seems to be a tendency for Seyfert galaxies to be closer to normal galaxies than to starbursts. The radial distribution of the molecular gas in these galaxies is compatible in most cases with a steeply decreasing function. Our high spatial resolution observations trace the interface region between the large scale properties of the disks of the host galaxies and the active nuclear regions. This interface region is the one most directly associated to the fuelling of the nuclear energy source in these objects and can be thus compared with data on samples of nonactive galaxies at similar spatial scales to deduce the possible relation of the circumnuclear gas contents and dynamics with nuclear activity (see Paper II).