Nuclear disks of gas and dust in Fanaroff-Riley type I radio host galaxies: 3C 402N and NGC 7052

A nuclear disk of gas and dust is detected in the host galaxy of the Fanaroff-Riley type I (FR-I) radio source 3C 402N, using pre-COSTAR HST/FOC images, and high spatial resolution ground-based broad-band and H alpha+[N II] narrowband images. The physical properties of the nuclear disk in the B2 2116+26 host galaxy (NGC 7052) are also presented. On average, the gas/dust disks in NGC 7052 and 3C 402N have a thickness of similar to 176 pc, and an elliptical shape with semimajor and semiminor axes similar to 555 PC and similar to 226 pc in size, respectively. The plane of the disks have an inclination of 68 degrees with respect to the plane of the sky, and their minor axes have an angular separation of similar to 38 degrees relative to the projected radio jet orientation. The amount of dust and ionized gas in the disks is M(dust) similar to 2.5 10(4) M. and M(gas) similar to 4 10(4) M., respectively. The inferred total mass of the disks is M(disk) N 2.5 10(6) M., if a gas-to-dust ratio of 100 is considered. The physical properties of the nuclear gas/dust disks in NGC 7052 and 3C 402N are similar to that of other nuclear disks in FR-I host galaxies like 3C 449. However, the size and mass of the NGC 7052 and 3C 402N disks is a factor 10 larger than that of the small nuclear disks recently discovered in M 87 (3C 274) and NGC 4261 (3C 270) with the HST. Nuclear disks of gas and dust are believed to play a central role in the feeding of a central massive black-hole. Detection and characterization of such disks is the first step towards a more deeply understanding of the interconnections between massive central black holes and their surrounding nuclear disks.