Ultra-fast outflows in radio-loud active galactic nuclei

TL;DR

This study investigates ultra-fast outflows in radio-loud active galactic nuclei, revealing their high incidence, diverse velocities, and ionization states, and demonstrating that jets do not prevent the presence of accretion disk winds.

Contribution

It extends the search for Fe K absorption lines to a larger sample of radio-loud AGNs, quantifies the incidence of UFOs, and characterizes their properties through photo-ionization modeling.

Findings

UFOs detected in >27% of sources, likely around 50%.

Outflow velocities range from <1,000 km/s to ~0.4c, with mean ~0.133c.

Material is highly ionized with N_H > 10^22 cm^-2.

Abstract

Recent X-ray observations show absorbing winds with velocities up to mildly-relativistic values of the order of ~0.1c in a limited sample of 6 broad-line radio galaxies. They are observed as blue-shifted Fe XXV-XXVI K-shell absorption lines, similarly to the ultra-fast outflows (UFOs) reported in Seyferts and quasars. In this work we extend the search for such Fe K absorption lines to a larger sample of 26 radio-loud AGNs observed with XMM-Newton and Suzaku. The sample is drawn from the Swift BAT 58-month catalog and blazars are excluded. X-ray bright FR II radio galaxies constitute the majority of the sources. Combining the results of this analysis with those in the literature we find that UFOs are detected in >27% of the sources. However, correcting for the number of spectra with insufficient signal-to-noise, we can estimate that the incidence of UFOs is this sample of radio-loud AGNs is likely in the range f=(50+/-20)%. A photo-ionization modeling of the absorption lines with XSTAR allows to estimate the distribution of their main parameters. The observed outflow velocities are broadly distributed between v_out<1,000 km s^-1 and v_out~0.4c, with mean and median values of v_out~0.133c and v_out~0.117c, respectively. The material is highly ionized, with an average ionization parameter of log\xi~4.5 erg s^-1 cm, and the column densities are larger than N_H > 10^22 cm^-2. Overall, these characteristics are consistent with the presence of complex accretion disk winds in a significant fraction of radio-loud AGNs and demonstrate that the presence of relativistic jets does not preclude the existence of winds, in accordance with several theoretical models.