Strong radio sources have been always identified with elliptical galaxies or recent merger remnants. Even recent studies have pointed to this (Urry and Padovani, 1995). When radio sources have been identified with spiral like galaxies, the radio emission has been seen to be confined to the nucleus and the disk rather than have extended structure. The emission is dominated by thermal emission from HII regions and supernovae winds.
Fanaroff and Riley (1974) classified powerful radio galaxies into FR I and FR II types based on their radio morphology. In both types, the extended radio structure is fueled by jets that transport the radio plasma from the nucleus.
Seyfert galaxies are almost always associated with spiral hosts
and in some cases
the radio emission is seen to be upto 
. Seyferts are towards the
low luminosity end of the radio galaxies and may form the bridge between
powerful radio galaxies and spirals. Meurs and Wilson (1984) have
studied the radio luminosity function of Seyferts, radio galaxies and spirals
and suggest that the luminosity functions do not smoothly merge.
We have shown here that in our radio galaxy sample there are five
sources ( 
) which can be classified as disky galaxies.
(There are additional sources with D/B;SPMgt;0.3 but with 
FWHM
of the PSF. We do not consider these to be disky galaxies, since
the ``disk'' cannot be distinguished from a point source.)
The
optical morphology of these objects is complex. Spiral arm like features
are visible in only one of them. Examples have been reported before
of spiral galaxies being associated with FR II radio sources. However, these
have turned out to be chance superpositions (see e.g.
Rönnback and Shaver, 1997). However, 1222-252 clearly seems to have
spiral like features.
Previous claims related to detection of disks in powerful radio galaxies have been controversial e.g. 3C 293 and 3C 305 both have a disk of rotating emission line gas but no evidence for a stellar disk (Heckman et al., 1985). 0313-192 in Abell 428 is an FR I source reported to be hosted by a disk dominated galaxy showing spiral arms in the B band (Ledlow et al., 1998). Barring a possible exception of 1053-282, all the disk dominated radio galaxies in our sample are FR II sources.
The D/B classification puts these galaxies in the Sa+ categories.
However, when the 
ratio is considered, it is clear that the
disks present in these galaxies are of a different nature than in
normal spiral galaxies, in which 
.
Except in one case, we do not see spiral structure in case
of the disky radio galaxies. However, we have seen above that
two more galaxies
show hints of spiral structure after they are operated on with the
morphological gradient filter.
An interesting example of the efficacy of the filter is the anonymous
galaxy shown in Figure 
. We believed at one time that this galaxy
was the host of the radio source MRC 0503-284. We found
subsequently that this was a misidentification, and the anonymous
galaxy was dropped from the sample.
Figure shows the direct B
image and the morphologically processed image of this galaxy.
The direct image clearly shows the presence of a spiral structure
to the south-east. There is a hint of an asymmetry towards the
north-west. The spiral structure in the south-east is seen much more
clearly after the image has passed through the morphological gradient.
In addition, the corresponding spiral structure in the north-west
also stands out. Thus, the
morphological gradient operator is clearly of help in detecting
spiral structure.
