Evidence for ultra-fast outflows in radio-quiet AGNs - I. Detection and statistical incidence of Fe K-shell absorption lines

By F. Tombesi, M. Cappi, J. Reeves, G. Palumbo, T. Yaqoob, V. Braito, M. Bologna, B. University, Jhu, NasaGsfc and 2 more. 2010

494 citations recorded by the source corpus.

Context. Blue-shifted Fe K absorption lines have been detected in recent years between 7 and 10 keV in the X-ray spectra of several radio-quiet AGNs. The derived blue-shifted velocities of the lines can often reach mildly relativistic values, up to 0.2–0.4c. These findings are important because they suggest the presence of a previously unknown massive and highly ionized absorbing material outflowing from their nuclei, possibly connected with accretion disk winds/outflows. Aims. The scope of the present work is to statistically quantify the parameters and incidence of the blue-shifted Fe K absorption lines through a uniform analysis on a large sample of radio-quiet AGNs. This allows us to assess their global detection significance and to overcome any possible publication bias. Methods. We performed a blind search for narrow absorption features at energies greater than 6.4 keV in a sample of 42 radio-quiet AGNs observed with XMM-Newton. A simple uniform model composed by an absorbed power-law plus Gaussian emission and absorption lines provided a good fit for all the data sets. We derived the absorption lines parameters and calculated their detailed detection significance making use of the classical F-test and extensive Monte Carlo simulations. Results. We detect 36 narrow absorption lines on a total of 101 XMM-Newton EPIC pn observations. The number of absorption lines at rest-frame energies higher than 7 keV is 22. Their global probability to be generated by random fluctuations is very low, less than 3 × 10 −8 , and their detection have been independently confirmed by a spectral analysis of the MOS data, with associated random probability 7 keV and to overcome their publication bias. These lines indicate that UFOs are a rather common phenomenon observable in the central regions of these sources and they are probably the direct signature of AGN accretion disk winds/ejecta. The detailed photo-ionization modeling of these absorbers is presented in a companion paper.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/b3545a6fa7430d73a92c58a98b1846d497deb46e

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Nuclear and High Energy Physics

Citations in the corpus

Unification of X-ray winds in Seyfert galaxies: from ultra-fast outflows to warm absorbers (2012, background): “It is important to note that Tombesi et al. (2010b, 2011b, 2012b) detected the presence of UFOs also in a small sample of (3 out of 5) radio-loud AGNs observed with Suzaku.”
BAT AGN Spectroscopic Survey. V. X-Ray Properties of the Swift/BAT 70-month AGN Catalog (2017, background): “The analysis of high-quality Suzaku and XMMNewton spectra has additionally pointed out that some objects also show highly ionized outflows with velocities exceeding 10,000 km s−1, the so-called ultra-fast outflows (e.g., Tombesi et al. 2010a,b; Gofford et al. 2013).”
Energy, momentum and mass outflows and feedback from thick accretion discs around rotating black holes (2013, background): “Observations of starburst galaxies (e.g. McNamara et al. 2006), and midly relativistic winds in AGN (Tombesi et al. 2010a,b) confirm this picture.”
CLEARING OUT A GALAXY (2012, background): “This strongly suggests that AGN activity is what sweeps galaxies clear of their gas on a dynamical timescale and makes them red and dead.”
The Suzaku View of Highly Ionized Outflows in AGN. 1; Statistical Detection and Global Absorber Properties (2012, background): “Moreover, such outflows have also been detected in a small sample of local broad line radio galaxies (BLRGs; Tombesi et al. 2010b, hereafter T10B) which thus suggests that they may represent an important addition to the commonly held AGN unification model (e.g. Antonucci 1993; Urry & Padovani 1995).”
DRIVING OUTFLOWS WITH RELATIVISTIC JETS AND THE DEPENDENCE OF ACTIVE GALACTIC NUCLEUS FEEDBACK EFFICIENCY ON INTERSTELLAR MEDIUM INHOMOGENEITY (2012, background): “Warm absorbers are observationally distinct from the ultrafast outflows (UFOs) detected in radio-quiet AGNs at high incidence (at least 35%; Tombesi et al. 2010) through highly ionized and blueshifted Fe K-shell absorption lines in the hard X-ray band (Cappi 2006).”
DISCOVERY OF ULTRA-FAST OUTFLOWS IN A SAMPLE OF BROAD-LINE RADIO GALAXIES OBSERVED WITH SUZAKU (2010, methodology): “In particular, a uniform and systematic search for blue-shifted Fe K absorption lines in a large sample of radio-quiet AGN observed with XMM-Newton has been performed by Tombesi et al. (2010).”
Kiloparsec-scale outflows are prevalent among luminous AGN: outflows and feedback in the context of the overall AGN population (2014, background): “…has shown that a highfraction, and potentially all, of high-accretion rate AGN drive highvelocity outflows (v ≈ 0.1c) close to their accretion disks (i.e., on sub-parsec scales; e.g., Blustin et al. 2003; Reeves et al. 2003; Ganguly & Brotherton 2008; Tombesi et al. 2010; Gofford et al. 2011).”
Mechanical AGN feedback: controlling the thermodynamical evolution of elliptical galaxies (2012, background): “…ISM mass (the active mass Mact, defined below) or perhaps that a wind originates from the accretion disc (Crenshaw, Kraemer & George 2003; Morganti et al. 2007; Nesvadba et al. 2008; Cappi et al. 2009; Cappi, Giustini & Tombesi 2011; Tombesi et al. 2010a,b, 2012; see also the references in G11a,b).”
Powerful Outflows and Feedback from Active Galactic Nuclei (2015, background): “In addition, the ‘hit rate’ of UFOs for multiply-observed AGN in the archival XMM-Newton data search (Tombesi et al. 2010) was relatively low, being 1 of 6 observations for NGC4151, MCG-6-30-15 (0/5), Mrk509 (3/5), NGC 4051(1/2), Mrk79 (1/3), Mrk205 (1/3), and Mrk290 (1/4).”
Gas expulsion by quasar-driven winds as a solution to the overcooling problem in galaxy groups and clusters (2010, background): “Indeed, there are already signs that such ‘quasar mode’ outflows are operating both at low and high redshift (see e.g. Moe et al. 2009; Dunn et al. 2010; Feruglio et al. 2010; Raimundo et al. 2010; Tombesi et al. 2010a,b).”
Numerical simulations of super-critical black hole accretion flows in general relativity (2013, background): “This mode of accretion is observed in quiescent AGN and in the low/hard state of X-ray binaries.”
CAUSE AND EFFECT OF FEEDBACK: MULTIPHASE GAS IN CLUSTER CORES HEATED BY AGN JETS (2011, background): “The velocity of AGN outflows is still poorly constrained and observations suggest values from several 103 to several 104 km s−1 (e.g., Crenshaw et al. 2003; Tombesi et al. 2010).”
The physics of galactic winds driven by active galactic nuclei (2012, background): “X-ray observations also find evidence for AGN winds with velocities ∼ 0.1c, albeit with lower significance and with more ambiguous interpretation (e.g., Chartas et al. 2002; Pounds et al. 2003; Tombesi et al. 2010).”
Suzaku observations of 'bare' active galactic nuclei (2012, background): “In addition, there has been growing evidence for AGN displaying highly blueshifted absorption features from highly ionized iron (see e.g. Tombesi et al. 2010), typically interpreted as evidence for rapid outflows (although see Gallo & Fabian 2011, for an alternative explanation).”