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

Abstract

Abstract We combine the most precise small-scale ($\lt 100\, \rm h^{-1}kpc$) quasar clustering constraints to date with recent measurements at large scales ($\gt 1\, \rm h^{-1}Mpc$) 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 $f_{\rm sat} = 0.071_{-0.004}^{+0.009}$ and minimum mass of $\rm M_{m} = 2.31_{-0.38}^{+0.41} \times 10^{12}\, \, \rm h^{-1} M_{\odot }$ 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.