SIMBAD references

We present the results of a K-band imaging survey of 40arcmin² in fields around 14 radio-loud active galactic nuclei (AGN), comprising six radio galaxies and eight quasars, with z>1.5. The survey, which is 80per cent complete to K<19.2mag and complemented by R-band imaging, aimed at investigating whether extremely red objects are present in excess around high-z AGN, and to study the environment of z>1.5 radio galaxies and radio-loud quasars. At 18<K<19mag, the differential galaxy counts in our fields suggest a systematic excess over the general field counts. At K<19.2mag we find an excess of galaxies with R-K>6 in comparison with the general field. Consistently, we also find that the R-K colour distribution of all the galaxies in the AGN fields is significantly redder than the colour distribution of the field galaxies. On the other hand, the distribution of the R-K colours is indistinguishable from that of galaxies taken from literature fields around radio-loud quasars at 1<z<2. We discuss the main implications of our findings and we compare the possible scenarios that could explain our results.