Moderate C_IV absorber systems require 10¹² M _⊙ dark matter halos at z ∼ 2.3: A cross-correlation study of C_IV absorber systems and quasars in SDSS-III boss DR9

We measure the two-point cross-correlation function of C IV absorber systems and quasars, using spectroscopic data from the Sloan Digital Sky Survey III Baryon Oscillation Spectroscopic Survey (BOSS; Data Release 9). The 19,701 quasars and 6149 C IV "moderate" absorbers, 0.28 Å < rest-frame equivalent width (EW) < 5 Å, in our study cover a redshift range of 2.1 < z < 2.5 over 3300 deg² and represent a factor of two increase in sample size over previous investigations. We find a correlation scale length and slope of the redshift-space cross-correlation function of s ₀ = 8.46 ± 1.24 Mpc, γ = 1.68 ± 0.19, in the redshift-space range 10 < s < 100 Mpc. We find a projected cross-correlation function of C IV absorption systems and quasars of r ₀ = 7.76 ± 2.80 Mpc, γ = 1.74 ± 0.21. We measure the combined quasar and C IV bias to be b _QSO b C _IV = 8.81 ± 2.28. Using an estimate of b _QSO from the quasar auto-correlation function we find b_CIV = 2.38 ± 0.62. This b_CIV implies that EW > 0.28 Å C IV absorbers at z ∼ 2.3 are typically found in dark matter halos that have masses ≥10^11.3-10^13.4 M _⊙ at that redshift. The complete BOSS sample will triple the number of both quasars and absorption systems and increase the power of this cross-correlation measurement by a factor of two.