We have analysed HST WFPC2 F555W and F814W ( i.e. , V and I ) images for fifteen elliptical galaxies with kinematically-distinct cores .
For each of them we have derived surface brightness and isophotal parameter profiles in the two bands , color maps , and radial profiles in V - I .
Most galaxies show patchy dust absorption close to their nuclei .
However , there are generally no indications of homogeneous , diffuse dust components close to the nuclei .
The nuclear colors in the unobscured regions are most likely representative of the central stellar populations .

We have detected photometric evidence for faint stellar disks , on scales of a few tens to a few arcseconds , in seven galaxies , namely NGC 1427 , 1439 , 1700 , 4365 , 4406 , 4494 and 5322 .
In NGC 1700 , the isophotes are slightly boxy at the scale of the counter-rotating component , and disky at larger radii .
We find no difference in V - I color greater than 0.02 mag between these disks and the surrounding galactic regions .
Hence the stellar populations in the kinematically distinct cores are not strongly deviant from the population of the main body .
Specifically , there is no evidence for a dominating population of blue , very metal weak stars , as predicted by some of the formation scenarios .
This argues against models in which small galaxies fall in and survive in the nuclei , unless super massive black holes are present .
These would in fact disrupt the accreted small systems .

For one galaxy , NGC 4365 , the innermost region is bluer than the surrounding regions .
This area extends to \sim 15 pc , and contains a luminosity of \sim 2.5 \times 10 ^ { 6 } L _ { \odot } .
If interpreted as a stellar population effect , an age difference of \sim 3-4 Gyrs , or an [ Fe / H ] variation of about 0.2 dex , is derived .

The nuclear intensity profiles show a large variety : some galaxies have steep cusp profiles , others have shallow cusps and a “ break radius ” .
The nuclear cusps of galaxies with kinematically-distinct cores follow the same trends as the nuclei of normal galaxies .

We have not been able to identify a unique , qualifying feature in the WFPC2 images which distinguish the galaxies with kinematically distinct cores from the kinematically normal cores .
It is possible that statistical differences exist : possibly , the kinematically distinct cores have a higher fraction of nuclear disks .
The similarity of both types of cores puts strong constraints on the formation scenarios .
Simulations of galaxy mergers , with the inclusion of star formation and nuclear black holes , are needed to resolve the question how these structures may have formed .
Spectra with high spatial resolution are needed to study the nuclear structure of the distinct component in detail .