Circumnuclear Keplerian disks in galaxies

In this Letter, we demonstrate the possibility of inferring the presence of Keplerian gaseous disks using properly equipped optical ground-based telescopes. We have modeled the peculiar bidimensional shape of the emission lines in a sample of five early-type disk galaxies as due to the motion of a gaseous disk rotating in the combined potential of a central pointlike mass and of an extended stellar disk. The value of the central mass concentration estimated for four galaxies of the sample (NGC 2179, NGC 4343, NGC 4435, and NGC 4459) is ~10^9 M_solar. This value, according to the assumptions made in our model, is overestimated. However, we have calculated that the effect is well within the errors. For the remaining galaxy, NGC 5064, an upper limit of 5x10^7 M_solar is estimated.