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

Abstract

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 Heα and/or Fe xxvi Lyα 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 6.7 keV in 20/51 sources at the P MC 95% level, which corresponds to ∼ 40% of the total sample. In all cases, individual absorption lines are detected independently and simultaneously amongst the two (or three) available XIS 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 Heα and Fe xxvi Lyα at a common velocity shift. From xstar fitting the mean column density and ionisation parameter for the Fe K absorption components are log(N H /cm −2 ) ≈ 23 and log(ξ/erg cm s −1 ) ≈ 4.5, respectively. Measured outflow velocities span a continuous range from < 1, 500 km s −1 up to ∼ 100, 000 km s −1 , with mean and median values of ∼ 0.1 c and ∼ 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-ionised circumnuclear material in a significant fraction of both radio-quiet and radio-loud AGN in the local universe.

Detection of a second high-velocity component in the highly ionized wind from PG 1211+143

“…Observational support for that picture is provided by recent archival searches (Tombesi et al 2010(Tombesi et al , 2011Gofford et al 2013) which find a substantial fraction of luminous AGN having a highly ionized wind with a velocity in the range ∼0.03-0.3c…”

“…Examination of archival data from XMM-Newton and Suzaku subsequently showed ultra-fast, highly-ionized outflows (UFOs) to be relatively common in nearby, luminous AGN (Tombesi 2010(Tombesi , 2011Gofford 2013). The frequency of these detections appeared to confirm a substantial covering factor, with a persistent wind having sufficient mechanical energy to disrupt the bulge gas in the host galaxy (Pounds 2014a).…”

“…Spectral modelling over a wider energy band reduces ambiguities in line identification, as first demonstrated in Pounds and Page (2006), while also providing additional outflow parameters, including the mean ionization parameter and column density. Such broad-band spectral modelling was used in the second paper on the XMM-Newton archival data (Tombesi et al (2011) and by Gofford (2013) in their similar analysis of Suzaku data.…”

The Complex Circumnuclear Environment of the Broad-Line Radio Galaxy 3c 390.3 Revealed by Chandra Hetg

“…A UFO with velocity v out ;0.15c was detected in 3C390.3 (Tombesi et al 2010bGofford et al 2013Gofford et al , 2015. The lower and upper limits on the distance, mass outflow rate, and mechanical power are d;0.002-0.02 pc,…”

“…This material can be observed in the X-ray spectra through blueshifted absorption lines from various elements over a wide range of ionizations, column densities, and velocities. The parameters of these winds range from logξ;0-4 erg s −1 cm, N H ;10 20 -10 22 cm −2 , and v out ∼100-1000 km s −1 for the socalled "warm absorbers" (WAs) (e.g., Halpern 1984;Nandra & Pounds 1992;Reynolds 1997;Crenshaw & Kraemer 2012;Tombesi et al 2013a;Kaastra et al 2014) to more extreme values of logξ;4-6 erg s −1 cm, N H ;10 22 -10 24 cm −2 , and v out ∼10,000-100,000 km s −1 for the so-called "ultrafast outflows" (UFOs; e.g., Tombesi et al 2010a; Gofford et al 2013). …”