Quasars as a tracer of large-scale structures in the distant universe

Hyunmi Song

We study the dependence of the number density and properties of quasars on the background galaxydensity using the currently largest spectroscopic datasets of quasars and galaxies. We construct agalaxy number density eld smoothed over the variable smoothing scale of between approximately10 and 20 Mpc/h 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 preparedfrom the SDSS-I/II DR7. We examine the correlation of incidence of quasars with the large-scalebackground density and dependence of quasar properties such as bolometric luminosity, black holemass, and Eddington ratio on the large-scale density. We find a monotonic correlation between thequasar number density and large-scale galaxy number density, which is fitted well with a power lawrelation, nQ \prop 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.