A search for relativistic outflows signatures in the X-ray spectra of radio-quiet AGNs

Tombesi, Francesco; Reeves, J. N.; Palumbo, G. G. C.; Yaqoob, T.; Braito, V.; Dadina, M.; Comastri, A.; Angelini, L.; Cappi, M.

doi:10.1063/1.3475250

Cited by 20 publications

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“…A substantial improvement is expected from the higher effective area and supreme energy resolution (down to ∼2−5 eV) in the Fe K band offered by the calorimeters on board the future Astro-H and IXO missions (e.g., Tombesi et al 2009). …”

Section: Discussionmentioning

confidence: 99%

Evidence for ultra-fast outflows in radio-quiet AGNs

Tombesi

Cappi²,

Reeves

et al. 2010

A&A

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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 <10 −7 . We identify the lines as Fe XXV and Fe XXVI K-shell resonant absorption. They are systematically blue-shifted, with a velocity distribution ranging from zero up to ∼0.3c, with a peak and mean value at ∼0.1c. We detect variability of the lines on both EWs and blue-shifted velocities among different XMM-Newton observations even on time-scales as short as a few days, possibly suggesting somewhat compact absorbers. Moreover, we find no significant correlation between the cosmological red-shifts of the sources and the lines blue-shifted velocities, ruling out any systematic contamination by local absorption. If we define ultra-fast outflows (UFOs) those highly ionized absorbers with outflow velocities higher than 10 4 km s −1 , then the majority of the lines are consistent with being associated to UFOs and the fraction of objects with detected UFOs in the whole sample is at least ∼35%. This fraction is similar for type 1 and type 2 sources. The global covering fraction of the absorbers is consequently estimated to be in the range C ∼ 0.4−0.6, thereby implying large opening angles. Conclusions. From our systematic X-ray spectral analysis on a large sample of radio-quiet AGNs we have been able to clearly assess the global veracity of the blue-shifted Fe K absorption lines at E > 7 keV and to overcome their publication bias. These lines indicate that UFOs are a rather ...

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Section: Discussionmentioning

confidence: 99%

Evidence for ultra-fast outflows in radio-quiet AGNs

Tombesi

Cappi²,

Reeves

et al. 2010

A&A

Self Cite

645

750

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“…However, the detection of line variability on a timescale less than 4 yr, suggesting a compact ∼parsec scale absorber, and the extreme parameters of the absorber, e.g., log ξ ∼ 3-4 erg s −1 cm and N H ∼ 10 22 -10 23 cm −2 , led Reeves et al (2008) to exclude such interpretation. As pointed out by the authors, the evidence of several other radio-quiet AGNs with Fe K absorption with associated blueshifted velocities higher than the relative cosmological redshift suggested that the case of PG 1211+143 was a mere coincidence (see also Tombesi et al 2010).…”

Section: Evidence For Ultra-fast Outflows In Blrgsmentioning

confidence: 99%

“…To quantify their significance, we computed the Δχ 2 deviations with respect to the baseline model (Section 3.1) over the whole 3.5-10.5 keV interval. The method is similar to the one used by the steppar command in XSPEC to visualize the error contours, but in this case the inner contours indicate higher significance than the outer ones (e.g., Miniutti & Fabian 2006;Miniutti et al 2007;Cappi et al 2009;Tombesi et al 2010).…”

Section: Fe K Absorption Line Searchmentioning

confidence: 99%

“…Moreover, it has been demonstrated that the F-test method can slightly overestimate the actual detection significance for a blind search of emission/absorption lines as it does not take into account the possible range of energies where a line might be expected to occur, nor does it take into account the number of bins (resolution elements) present over that energy range (e.g., Protassov et al 2002). This problem requires an additional test on the red/blueshifted lines significance and can be solved by determining the unknown underlying statistical distribution by performing extensive Monte Carlo (MC) simulations (e.g., Porquet et al 2004;Yaqoob & Serlemitsos 2005;Miniutti & Fabian 2006;Markowitz et al 2006;Cappi et al 2009;Tombesi et al 2010).…”

Section: Line Significance From Monte Carlo Simulationsmentioning

confidence: 99%

“…The energies of these absorption lines are systematically blueshifted and the corresponding velocities can reach up to mildly relativistic values of ∼0.2-0.4c. In particular, a uniform and systematic search for blueshifted Fe K absorption lines in a large sample of radio-quiet AGNs observed with XMM-Newton has been performed by Tombesi et al (2010). This allowed the authors to assess their global detection significance and to overcome any possible publication bias (e.g., Vaughan & Uttley 2008).…”

Section: Introductionmentioning

confidence: 99%

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DISCOVERY OF ULTRA-FAST OUTFLOWS IN A SAMPLE OF BROAD-LINE RADIO GALAXIES OBSERVED WITHSUZAKU

Tombesi

Sambruna

Reeves

et al. 2010

ApJ

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175

180

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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 v 0.04-0.15c. A fit with specific photoionization models gives ionization parameters in the range log ξ 4-5.6 erg s −1 cm and column densities of N H 10 22 -10 23 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.

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Exploring accretion disk physics and black hole growth with regular monitoring of ultrafast active galactic nucleus winds

2017

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Fifteen years of XMM-Newton observations have established that ultrafast highly ionized winds (UFOs) are common in radio-quiet active galactic nucleus (AGN). A simple theory of Eddington-limited accretion correctly predicts the typical velocity (∼0.1c) and high ionization of such winds, with observed flow energy capable of ejecting star-forming gas. An extended XMM-Newton observation of the archetypal UFO PG 1211+143 recently found a more complex flow pattern, suggesting that intensive XMM-Newton observations offer exciting potential for probing the inner accretion disk structure and super-massive black hole (SMBH) growth.

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A search for relativistic outflows signatures in the X-ray spectra of radio-quiet AGNs

Cited by 20 publications

References 0 publications

Evidence for ultra-fast outflows in radio-quiet AGNs

Evidence for ultra-fast outflows in radio-quiet AGNs

DISCOVERY OF ULTRA-FAST OUTFLOWS IN A SAMPLE OF BROAD-LINE RADIO GALAXIES OBSERVED WITHSUZAKU

Exploring accretion disk physics and black hole growth with regular monitoring of ultrafast active galactic nucleus winds

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