All Tables

• Table 1: Summary of data from the literature for our sample. The spectral classification is from Willott's catalog at the URL http://www-astro.physics.ox.ac.uk/~cjw/3crr/3crr.html, except (^a) for which we used the classification published in Jackson & Rawlings (1997) (spectra by Jackson & Browne 1991, for 3C 345, Tadhunter et al. 1993, for 3C 327.1 and Spinrad et al. 1985, for the rest) and (^b) for which we report the classification available in the NASA/IPAC Extragalactic Database (no references for the spectra).
• Table 2: Log of HST observations.
• Table 3: Result from identification and photometry of central compact cores in our sample.
• Table 4: Summary of the optical properties of the sources at 0.4<z<0.6 observed with HST and results of our study on the images. Note that only one source of our sample (classified as HEG) has no HST data available (3C 327.1). 3C 275 has also been excluded because of a cosmic ray event in the central region of the HST image (see text, Sect.3).