The luminosity dependence of ultraviolet absorption in active galactic nuclei.
LAOR A. and BRANDT W.N.
Abstract (from CDS):
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 αox≤-2) show the strongest UV absorption at a given luminosity, and their maximum outflow velocity, vmax, is strongly correlated with MV (rS=-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 in SXWQs.