Citation:
Abstract:
We present the first measurement of the spatial clustering ofmid-infrared-selected obscured and unobscured quasars, using a sample inthe redshift range 0.7 < z < 1.8 selected from the 9deg2 Boötes multiwavelength survey. Recently, theSpitzer Space Telescope and X-ray observations have revealed largepopulations of obscured quasars that have been inferred from models ofthe X-ray background and supermassive black hole evolution. To date,little is known about obscured quasar clustering, which allows us tomeasure the masses of their host dark matter halos and explore theirrole in the cosmic evolution of black holes and galaxies. In this study,we use a sample of 806 mid-infrared-selected quasars and ≈250,000galaxies to calculate the projected quasar-galaxy cross-correlationfunction wp (R). The observed clustering yieldscharacteristic dark matter halo masses of log(M halo [h-1 M sun]) = 12.7+0.4-0.6and 13.3+0.3-0.4 for unobscured quasars (QSO-1s)and obscured quasars (Obs-QSOs), respectively. The results for QSO-1sare in excellent agreement with previous measurements for opticallyselected quasars, while we conclude that the Obs-QSOs are at least asstrongly clustered as the QSO-1s. We test for the effects of photometricredshift errors on the optically faint Obs-QSOs, and find that ourmethod yields a robust lower limit on the clustering; photo-z errors maycause us to underestimate the clustering amplitude of the Obs-QSOs by at