8 Conclusions

We presented the results of deep IR imaging for three subsamples of radio sources of the WENSS catalogue: 36 USS, 14 GPS and 13 FS sources. We show images in the J- or K-bands of the identified objects: 29 USS sources, 13 GPS sources and 10 FS sources. We have found IR counterparts for 44% of USS sources, 93% of GPS sources and 77% of FS sources. In addition, there are uncertain IR counterparts for 36% of USS sources and 15% of FS sources. In some cases, we find the IR counterparts of radio sources still lacking optical identifications. We remark that for the USS sources we find a larger percentage of certain IR identifications for the A and B sub-samples than for the high flux control sub-sample C.

We analyse the IR-radio alignment effect on 15 USS and 9 GPS radio galaxies and we do not find evidence for an alignment of the IR morphology with the radio axis.

Finally, we present the J-band image of the gravitational lens system 1600+434, before and after subtraction of the quasar images. This procedure allows us to provide an estimate of the J- and K-magnitudes of the lensing galaxy.

Acknowledgements

We thank Ruggero Stanga and Carlo Baffa for their support to the observations with ARNICA at the NOT (La Palma). We are grateful to Leslie Hunt for her kindness in helping with the data reduction, and to Richard Hook for providing the "drizzling'' software. We thank George Miley for the hospitality at the Sterrewacht Observatory of Leiden and Malcolm Bremer, Andrea Cimatti, Roeland Rengelink and Ignas Snellen for useful discussions and for providing unpublished data.