DOIAbstract
We have conducted a NIR study of the environments of seven radio-loud quasars at redshifts $1<z<1.6$. In present paper we describe deep K band images obtained for the fields of $\sim6\times6$ arcmin around the quasars with 3σ limiting magnitudes of $K\sim20.5$. These fields were previously studied using deep B and R band images (Sánchez & González-Serrano 1999). Using optical and NIR data together, a significant excess of galaxies has been found whose optical-NIR colours, luminosity, spatial scale, and number of galaxies are compatible with clusters at the redshift of the quasar. We have selected a sample of cluster candidates analyzing the $R-K$ vs. K diagram. A ~25% of the candidates present red optical-NIR colours and an ultraviolet exce...
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