Ratio of radio luminosity of the core and of extended emission as a function of total radio luminosity at 1400 MHz of 21 remnant candidates. The green line represents the relation from de Ruiter et al. (1990), corrected for H₀. Markers filled with colour are the ones with less reliable redshift, affecting the total radio luminosity (see Table 1). Points filled with a yellow star symbol represent sources with USS. Sources with ‘✗’ written inside them are those with observed hotspots at 150 MHz (see Sect. 6.3). ‘UL’ in the legend stands for the ‘upper limit value’.