Bulges and disks in the Host Galaxies of low redshift 3CR Sources: a near-IR view of their radial brightness profile

We analyze the near-infrared luminosity profiles and photometric parameters of the host galaxies of 3CR radio sources with z<0.3, to investigate their physical nature. Our sample includes 82 galaxies, of which 22 (27%) are FR Is and 60 (73%) are FR IIs. Using near-infrared data taken both with NICMOS onboard the Hubble Space Telescope and from the ground with the Telescopio Nazionale Galileo, we find that luminosity profiles are very well described by a single Sersic law in 52% of the cases and for the remaining objects (48%) it is necessary to include an exponential profile, which could indicate the presence of a disk. The average bulge to disk luminosity ratio for the galaxies is (b/d) ~ 1.1. The analysis of the photometric parameters of the sub samples indicates that FR Is and FR IIs show rather similar bulges in terms of effective surface magnitude, effective radius, and Sersic index. On the other hand, disks in FR Is and FR IIs hosts show, on average, different properties. Central surface magnitudes are dimmer and scale lengths are greater by a factor of 2 in FR Is when compared to FR IIs. We also estimate the black hole mass associated with each galaxy using two different methods that claim tight correlations between the black hole mass (M_BH) with the infrared bulge luminosity (L_bulge) and with the Sersic index (n). Our data indicate that masses obtained through these two methods show a high dispersion and M_BH obtained through L_bulge are systematically higher (by a factor of ~3) than those obtained using n. This result may reflect the fact that for our sample galaxies we do not find any correlation between L_bulge and n.