A Compton-thick Wind in the High-luminosity Quasar, PDS 456

PDS 456 is a nearby (z = 0.184), luminous (L _bol ~ 10⁴⁷ erg s^-1) type I quasar. A deep 190 ks Suzaku observation in 2007 February revealed the complex, broadband X-ray spectrum of PDS 456. The Suzaku spectrum exhibits highly statistically significant absorption features near 9 keV in the quasar rest frame. We show that the most plausible origin of the absorption is from blueshifted resonance (1s-2p) transitions of hydrogen-like iron (at 6.97 keV in the rest frame). This indicates that a highly ionized outflow may be present moving at near relativistic velocities (~ 0.25c). A possible hard X-ray excess is detected above 15 keV with the Hard X-ray Detector (at 99.8% confidence), which may arise from high column density gas (N _H > 10²⁴ cm^-2) partially covering the X-ray emission, or through strong Compton reflection. Here we propose that the iron K-shell absorption in PDS 456 is associated with a thick, possibly clumpy outflow, covering about 20% of 4π steradian solid angle. The outflow is likely launched from the inner accretion disk, within 15-100 gravitational radii of the black hole. The kinetic power of the outflow may be similar to the bolometric luminosity of PDS 456. Such a powerful wind could have a significant effect on the co-evolution of the host galaxy and its supermassive black hole, through feedback.