The Luminosity Dependence of Ultraviolet Absorption in Active Galactic Nuclei

Abstract

We describe the results of a survey of the UV absorption properties of the Boroson & Green sample of active galactic nuclei (AGNs), which extends from the Seyfert (MV ’?21) to the luminous quasar (MV ’?27) level. The survey is based mostly on Hubble Space Telescope archival data available for &1 2 of the 87 sample objects. Our main result is that soft X-ray–weak quasars (SXWQs; 10 AGNs with ?ox ??2) show the strongest UV absorption at a given luminosity, and their maximum outflow velocity, vmax,is strongly correlated withMV (rS ¼?0:95). This suggests that vmax is largely set by the luminosity, as expected for radiation pressure–driven outflows. Luminous SXWQs have preferentially low [O iii] luminosity, which suggests that they are physically distinct from unabsorbed AGNs, while non-SXWQs with UV absorption are consistent with being drawn from the unabsorbed AGN population. We also find an indication that vmax=vBLR increases with L=LEdd, as expected for radiation pressure–driven outflows. This relation and the vmax versus MV relation may indicate that the radiation-pressure force multiplier increases with luminosity and that the wind-launching radius in non-SXWQs is?10 times larger than inSXWQs