Quasars as a tracer of large-scale structures in the distant universe
  We study the dependence of the number density and properties of quasars on
the background galaxy density using the currently largest spectroscopic
datasets of quasars and galaxies. We construct a galaxy number density field
smoothed over the variable smoothing scale of between approximately 10 and
$20\,h^{-1}$Mpc over the redshift range of $0.46<z<0.59$ using the Sloan
Digital Sky Survey (SDSS) Data Release 12 (DR12) Constant MASS (CMASS)
galaxies. The quasar sample is prepared from the SDSS I/II DR7. We examine the
correlation of incidence of quasars with the large-scale background density and
dependence of quasar properties such as bolometric luminosity, black hole mass,
and Eddington ratio on the large-scale density. We find a monotonic correlation
between the quasar number density and large-scale galaxy number density, which
is fitted well with a power law relation, $n_Q\propto\rho_G^{0.618}$. We detect
weak dependences of quasar properties on the large-scale density such as a
positive correlation between black hole mass and density, and a negative
correlation between luminosity and density. We discuss the possibility of using
quasars as a tracer of large-scale structures at high redshifts, which may be
useful for studies of growth of structures in the high redshift universe.
