The Connection between Ultraviolet and X-ray Outflows in AGN: the case of PDS 456

High-velocity outflows from AGN are a well-known phenomena in terms of the Broad Absorption Lines seen in the UV/optical. More recently, similar, possibly related, outflows have been reported in the X-ray. The most extreme example is seen in the nearby, luminous QSO PDS 456, which displays a massive, high velocity (50000 km s-1), high-ionization X-ray outflow of 10 solar masses yr-1. Here we present the UV spectrum of PDS 456 as observed by the Hubble Space Telescope. We find the UV spectrum is also extreme, displaying very broad emission-lines, with CIV 1549 blueshifted by 5000 km s-1 and a broad Ly-alpha absorption trough blueshifted by 14000-24000 km s-1. No strong, broad high-ionization absorption features are seen. We interpret the combined UV and X-ray spectrum of PDS 456 as the signature of a decelerating, cooling outflow, which may be driven by radiation and/or magnetic field. This outflow may be the source of some of the broad emission and absorption-line gas.