(NLR), presumably driven by radio jets or outflows; an example is 3C 48 [@Cha99; @Sto07]. In addition, many CSS sources show distorted radio structures, suggestive of violent interaction between the jet and the ambient interstellar medium [@Wil84; @Fan85; @Nan91; @Spe91; @Nan92; @Aku91]. The ample supply of cold gas in their host galaxies and their strong radio activity, which results in a detection rate as high as $\sim30$ per cent in flux-density limited radio source surveys [@Pea82; @Fan90], make CSS sources good laboratories for the study of AGN triggering and feedback.

3C 48 ($z=0.367$) is associated with the first quasar to be discovered [@Mat61; @Gre63] in the optical band. Its host galaxy is brighter than that of most other low redshift quasars. The radio source 3C 48 is classified as a CSS source due to its small size and steep radio spectrum [@Pea82]. Optical and NIR spectroscopic observations suggest that the active nucleus is located in a gas-rich environment and that the line-emitting gas clouds are interacting with the jet material [@Can90; @Sto91; @Cha99; @Zut04; @Kri05; @Sto07]. VLBI images [@Wil90; @Wil91; @Nan91; @Wor04] have revealed a disrupted jet in 3C 48, indicative of strong interactions between the jet flow and the 