2018ApJ...865...90M

We analyze new HST/COS spectra for two quasar absorption outflows seen in the quasi-stellar object LBQS 1206+1052. These data cover, for the first time, absorption troughs from S IV, Si II, and P V. From the ratio of the S IV* to S IV column densities, we measure the electron number density of the higher-velocity (-1400 km s^–1, v1400) outflow to be log(n_e)=4.23_–0.09^+0.09 cm^–3 and constrain the lower-velocity (-730 km s^–1, v700) outflow to log(n_e) > 5.3 cm^–3. The n_e associated with the higher-velocity outflow is an order of magnitude larger than reported in prior work. We find that the previous measurement was unreliable since it was based on density-sensitive absorption troughs that were likely saturated. Using photoionization models, we determine the best χ²-minimization fit for the ionization parameter and hydrogen column density of the higher-velocity outflow: log(U_H)=-1.73_–0.12^+0.21 and log(N_H)=21.03_–0.15^+0.25 cm^–2, respectively. We calculate from U_H and n_e a distance of 500_–110⁺¹⁰⁰ pc from the central source to the outflow. Using an SED attenuated by the v700 outflow yields a two-phase photoionization solution for the v1400 outflow, separated by a ΔU ~= 0.7. Otherwise, the resultant distance, mass flux, and kinetic luminosity are similar to the unattenuated case. However, the attenuated analysis has significant uncertainties due to a lack of constraints on the v700 outflow in 2017.