The density of extremely red objects around high-z radio-loud AGN
  We present the results of a K-band imaging survey of 40 arcmin^{2} in fields around 14 radio-loud AGN (6 radio galaxies and 8 quasars) with z>1.5. The survey, 80% complete to K<19.2 and complemented by R-band imaging, aimed at investigating whether extremely red objects (EROs) are present in excess around high-z AGN, and to study the environment of z>1.5 radio galaxies and radio-loud quasars. At $18<K<19$ the differential galaxy counts in our fields suggest a systematic excess over the general field counts. At K<19.2, we find an excess of galaxies with R-K>6 compared to the general field. Consistently, we also find that the R-K colour distribution of all the galaxies in the AGN fields are significantly redder than the colour distribution of the field galaxies. On the other hand, the distribution of the R-K colours is undistinguishable 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 which could explain our results. 
A. Cimatti (Arcetri), D. Villani (Firenze), L. Pozzetti (Arcetri), S.   di Serego Alighieri (Arcetri)