The Suzaku view of highly ionized outflows in AGN - I. Statistical detection and global absorber properties

We present the results of a new spectroscopic study of Fe K-band absorption in active galactic nuclei (AGN). Using data obtained from the Suzaku public archive we have performed a statistically driven blind search for Fe XXV He alpha and/or Fe XXVI Ly alpha absorption lines in a large sample of 51 Type 1.0-1.9 AGN. Through extensive Monte Carlo simulations we find that statistically significant absorption is detected at E greater than or similar to 6.7 keV in 20/51 sources at the P-MC = 95 per cent level, which corresponds to similar to 40 per cent of the total sample. In all cases, individual absorption lines are detected independently and simultaneously amongst the two (or three) available X-ray imaging spectrometer detectors, which confirms the robustness of the line detections. The most frequently observed outflow phenomenology consists of two discrete absorption troughs corresponding to Fe XXV He alpha and Fe XXVI Ly alpha at a common velocity shift. From xstar fitting the mean column density and ionization parameter for the Fe K absorption components are log (N-H/cm(-2)) approximate to 23 and log (xi/erg cm s(-1)) approximate to 4.5, respectively. Measured outflow velocities span a continuous range from < 1500 km s(-1) up to similar to 100 000 km s(-1), with mean and median values of similar to 0.1 c and similar to 0.056 c, respectively. The results of this work are consistent with those recently obtained using XMM-Newton and independently provides strong evidence for the existence of very highly ionized circumnuclear material in a significant fraction of both radio-quiet and radio-loud AGN in the local universe.