Discovery of ultra-fast outflows in a sample of broad-line radio galaxies observed with Suzaku

Abstract

We present the results of a uniform and systematic search for blueshifted Fe K absorption lines in the X-ray spectra of five bright broad-line radio galaxies observed with Suzaku. We detect, for the first time in radio-loud active galactic nuclei (AGNs) at X-rays, several absorption lines at energies greater than 7 keV in three out of five sources, namely, 3C 111, 3C 120, and 3C 390.3. The lines are detected with high significance according to both the F-test and extensive Monte Carlo simulations. Their likely interpretation as blueshifted Fe xxv and Fe xxvi K-shell resonance lines implies an origin from highly ionized gas outflowing with mildly relativistic velocities, in the range ν ≃ 0.04-0.15c. A fit with specific photoionization models gives ionization parameters in the range log ℰ ≃ 4-5.6 erg s-1 cm and column densities of NH ≃ 1022-1023 cm-2. These characteristics are very similar to those of the ultra-fast outflows (UFOs) previously observed in radio-quiet AGNs. Their estimated location within ∼0.01-0.3 pc of the central super-massive black hole suggests a likely origin related with accretion disk winds/outflows. Depending on the absorber covering fraction, the mass outflow rate of these UFOs can be comparable to the accretion rate and their kinetic power can correspond to a significant fraction of the bolometric luminosity and is comparable to their typical jet power. Therefore, these UFOs can play a significant role in the expected feedback from the AGN to the surrounding environment and can give us further clues on the relation between the accretion disk and the formation of winds/jets in both radio-quiet and radio-loud AGNs. © 2010. The American Astronomical Society. All rights reserved.