Seminars and Colloquia at ESO Garching and on the campus
Powerful quasars can be seen out to large distances. As they reside in massive dark matter haloes, they provide a useful tracer of large-scale structure. Stacking far-infrared and sub-millimeter maps on the locations of quasars has proved a useful tool in studying quasars and their environments. We stack Herschel-SPIRE images at 250, 350, and 500 μm at the location of 11,235 quasars in 10 redshift bins spanning 0.5 ≤ z ≤ 3.5. The unresolved dust emission of the quasar and its host galaxy dominate on instrumental beam scales, while extended emission is spatially resolved on physical scales of order a megaparsec. This emission is due to dusty star-forming galaxies (DSFGs) clustered around the dark matter haloes hosting quasars. We measure radial surface brightness profiles of the stacked images to compute the angular correlation function of DSFGs correlated with quasars. We then model the profiles to determine large-scale clustering properties of quasars and DSFGs as a function of redshift. We adopt a halo model and parametrize it by the most effective halo mass at hosting star-forming galaxies, finding log(M_eff/M_⊙)=(13.8+/0.1) at z = 2.21-2.32, and, at z = 0.5-0.81, the mass is log(M_eff/M_⊙)=(10.7+/-0.2). Our results indicate a downsizing of dark matter haloes hosting DSFGs between 0.5 ≤ z ≲ 2.9. The derived dark matter halo masses are consistent with other measurements of star-forming and sub-millimeter galaxies. The physical properties of DSFGs inferred from the halo model depend on details of the quasar halo occupation distribution in ways that we explore at z > 2.5, where the quasar HOD parameters are not well constrained.