A Compton-Thick Wind in the High-Luminosity Quasar, PDS 456

PDS 456 is a nearby ( z = 0.184), luminous ( L bol ∼ 10 47 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 (1 s –2 p ) 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 (∼ 0.25 c ). 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 > 10 24 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.