The density of extremely red objects around high-z radio-loud active galactic nuclei

We present the results of a K-band imaging survey of 40arcmin 2 in fields around 14 radioloud 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 2 K . 6 in comparison with the general field. Consistently, we also find that the R 2 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 2 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.