A Halo Occupation Interpretation of Quasars at z ∼1.5 Using Very Small-Scale Clustering Information

Abstract

We combine the most precise small-scale (< 100 h-1kpc) quasar clustering constraints to date with recent measurements at large scales (> 1h-1Mpc) from the extended Baryon Oscillation Spectroscopic Survey (eBOSS) to better constrain the satellite fraction of quasars at z ∼1.5 in the halo occupation formalism. We build our Halo Occupation Distribution (HOD) framework based on commonly used analytic forms for the one and two-halo terms with two free parameters: the minimum halo mass that hosts a central quasar and the fraction of satellite quasars that are within one halo. Inspired by recent studies that propose a steeper density profile for the dark matter haloes that host quasars, we explore HOD models at kiloparsec scales and best-fit parameters for models with 10 × higher concentration parameter. We find that an HOD model with a satellite fraction of fsat = 0.071-0.004+0.009 and minimum mass of Mm = 2.31-0.38+0.41 × 1012 h-1M⊙ for the host dark matter haloes best describes quasar clustering (on all scales) at z ∼1.5. Our results are marginally inconsistent with earlier work that studied brighter quasars, hinting at a luminosity-dependence to the one-halo term.