Environments of Nearby Quasars in Sloan Digital Sky Survey
  For the first time spectroscopic galaxy redshift surveys are reaching the
scales where galaxies can be studied together with the nearest quasars. This
gives an opportunity to study the dependence between the activity of a quasar
and its environment in a more extensive way than before. We study the spatial
distribution of galaxies and groups of galaxies in the environments of low
redshift quasars in the Sloan Digital Sky Survey (SDSS). Our aim is to
understand how the nearby quasars are embedded in the local and global density
field of galaxies and how the environment affects quasar activity. We analyse
the environments of nearby quasars using number counts of galaxies. We also
study the dependence of group properties to their distance to the nearest
quasar. The large scale environments are studied by analysing the locations of
quasars in the luminosity density field. Our study of the number counts of
galaxies in quasar environments shows an underdensity of bright galaxies at a
few Mpc from quasars. Also, the groups of galaxies that have a quasar closer
than 2Mpc are poorer and less luminous than in average. Our analysis on the
luminosity density field shows that quasars clearly avoid rich superclusters.
Nearby quasars seem to be located in outskirts of superclusters or in filaments
connecting them. Our results suggest that quasar evolution may be affected by
density variations both on supercluster scales and in the local environment.
