Bulges and disklike components in the host galaxies of low-redshift 3CR sources: A near-infrared view of their radial brightness profiles

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 on board 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 that for the remaining objects ( 48%) it is necessary to include an exponential profile, which indicates the presence of a second disklike component. The average bulge-to-disklike components luminosity ratio for the galaxies is (b/e) similar to 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, the disklike components in FR I and FR II 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 of 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 that MBH obtained through Lbulge are systematically higher ( by a factor of similar to 3) than those obtained using n. This result may reflect the fact that for our sample galaxies we do not find any correlation between Lbulge and n.