Overdensity of galaxies in the environment of quasar pairs
  We report on a study of the galaxy environments of low redshift physical
quasars pairs. We selected 20 pairs having projected separation $<$ 0.5 Mpc and
difference of systemic velocity $<$ 800 km s$^{-1}$. Using Sloan Digital Sky
Survey images we evaluated the galaxy overdensity around these quasars in pairs
and then compare it with that of a sample of isolated quasars with same
redshift and luminosity. It is found that on average there is a systematic
larger overdensity of galaxies around quasars in pairs with respect to that of
isolated quasars. This may represent a significant link between nuclear
activity and galaxy environment. However, at odds with that, the closest quasar
pairs seem to inhabit poorer environments. Implications of present results and
perspectives for future work are briefly discussed.
