The Spitzer Extragalactic Representative Volume Survey (SERVS): The   Environments of High-z SDSS Quasi-Stellar-Objects
  This paper presents a study of the environments of SDSS Quasi-Stellar-Objects (QSOs) in the Spitzer Extragalactic Representative Volume Survey (SERVS). We concentrate on the high-redshift QSOs as these have not been studied in large numbers with data of this depth before. We use the IRAC 3.6-4.5{\mu}m colour of objects and ancillary r-band data to filter out as much foreground contamination as possible. This technique allows us to find a significant (> 4-{\sigma}) over-density of galaxies around QSOs in a redshift bin centred on z ~ 2.0 and a (> 2-{\sigma}) over-density of galaxies around QSOs in a redshift bin centred on z ~ 3.3. We compare our findings to the predictions of a semi-analytic galaxy formation model, based on the {\Lambda}CDM millennium simulation, and find for both redshift bins that the model predictions match well the source-density we have measured from the SERVS data. 
J. T. Falder, J. A. Stevens, Matt J. Jarvis, D. G. Bonfield, M. Lacy,   D. Farrah, S. Oliver, J. Surace, J.-C. Mauduit, M. V...
astro-ph.CO