V. Braito

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

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.

The XMM-Newton serendipitous survey - VII. The third XMM-Newton serendipitous source catalogue

© ESO, 2016.Context. Thanks to the large collecting area (3 × ∼1500 cm2 at 1.5 keV) and wide field of view (30′ across in full field mode) of the X-ray cameras on board the European Space Agency X-ray observatory XMM-Newton, each individual pointing can result in the detection of up to several hundred X-ray sources, most of which are newly discovered objects. Since XMM-Newton has now been in orbit for more than 15 yr, hundreds of thousands of sources have been detected. Aims. Recently, many improvements in the XMM-Newton data reduction algorithms have been made. These include enhanced source characterisation and reduced spurious source detections, refined astrometric precision of sources, greater net sensitivity for source detection, and the extraction of spectra and time series for fainter sources, both with better signal-to-noise. Thanks to these enhancements, the quality of the catalogue products has been much improved over earlier catalogues. Furthermore, almost 50% more observations are in the public domain compared to 2XMMi-DR3, allowing the XMM-Newton Survey Science Centre to produce a much larger and better quality X-ray source catalogue. Methods. The XMM-Newton Survey Science Centre has developed a pipeline to reduce the XMM-Newton data automatically. Using the latest version of this pipeline, along with better calibration, a new version of the catalogue has been produced, using XMM-Newton X-ray observations made public on or before 2013 December 31. Manual screening of all of the X-ray detections ensures the highest data quality. This catalogue is known as 3XMM. Results. In the latest release of the 3XMM catalogue, 3XMM-DR5, there are 565 962 X-ray detections comprising 396 910 unique X-ray sources. Spectra and lightcurves are provided for the 133 000 brightest sources. For all detections, the positions on the sky, a measure of the quality of the detection, and an evaluation of the X-ray variability is provided, along with the fluxes and count rates in 7 X-ray energy bands, the total 0.2-12 keV band counts, and four hardness ratios. With the aim of identifying the detections, a cross correlation with 228 catalogues of sources detected in all wavebands is also provided for each X-ray detection. Conclusions. 3XMM-DR5 is the largest X-ray source catalogue ever produced. Thanks to the large array of data products associated with each detection and each source, it is an excellent resource for finding new and extreme objects.

The Suzaku View of Highly Ionized Outflows in AGN. 1; 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 Fexxv He and/or Fexxvi Ly absorption lines in a large sample of 51 type 1:0 1:9 AGN. Through extensive Monte Carlo simulations we nd that statistically signicant absorption is detected at E & 6:7 keV in 20/51 sources at the PMC > 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 conrms the robustness of the line detections. The most frequently observed outow phenomenology consists of two discrete absorption troughs corresponding to Fexxv He and Fexxvi Ly at a common velocity shift. From xstar tting the mean column density and ionisation parameter for the Fe K absorption components are log(NH=cm 2 ) 23 and log(= erg cm s 1 ) 4:5, respectively. Measured outow 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 signicant fraction of both radio-quiet and radio-loud AGN in the local universe.

Evidence for ultrafast outflows in radio-quiet AGNs – III. Location and energetics

Using the results of a previous X-ray photo-ionization modelling of blue-shifted Fe K absorption lines on a sample of 42 local radio-quiet AGNs observed with XMM-Newton, in this letter we estimate the location and energetics of the associated ultrafast outflows (UFOs). Due to significant uncertainties, we are essentially able to place only lower/upper limits. On average, their location is in the interval approx.0.0003-0.03pc (approx.10(exp 2)-10(exp 4)tau(sub s) from the central black hole, consistent with what is expected for accretion disk winds/outflows. The mass outflow rates are constrained between approx.0.01- 1 Stellar Mass/y, corresponding to approx. or >5-10% of the accretion rates. The average lower-upper limits on the mechanical power are logE(sub K) approx. or = 42.6-44.6 erg/s. However, the minimum possible value of the ratio between the mechanical power and bolometric luminosity is constrained to be comparable or higher than the minimum required by simulations of feedback induced by winds/outflows. Therefore, this work demonstrates that UFOs are indeed capable to provide a significant contribution to the AGN r.osmological feedback, in agreement with theoretical expectations and the recent observation of interactions between AGN outflows and the interstellar medium in several Seyferts galaxies .

Black hole feedback in the luminous quasar PDS 456

Finding the necessary negative feedback The evolution of galaxies seems to be tied to the growth of the supermassive black holes at their centers, but its not entirely clear why. Models have suggested a mechanism in which the growth of the black hole results in an outflow of gas that interrupts star formation. However, evidence for enough of this negative feedback has been lacking. Nardini et al. now see a signature in x-ray spectra of a strong persistent outflow in the quasar PDS 456. They estimate a broad solid angle spanned by the wind that enables a far greater impact on the host galaxy than narrower jet outflows. Science, this issue p. 860 A broad wind outflow from an accreting supermassive black hole could stunt star formation in its host galaxy. The evolution of galaxies is connected to the growth of supermassive black holes in their centers. During the quasar phase, a huge luminosity is released as matter falls onto the black hole, and radiation-driven winds can transfer most of this energy back to the host galaxy. Over five different epochs, we detected the signatures of a nearly spherical stream of highly ionized gas in the broadband x-ray spectra of the luminous quasar PDS 456. This persistent wind is expelled at relativistic speeds from the inner accretion disk, and its wide aperture suggests an effective coupling with the ambient gas. The outflow’s kinetic power larger than 1046 ergs per second is enough to provide the feedback required by models of black hole and host galaxy coevolution.

A Suzaku survey of Fe K lines in Seyfert 1 active galactic nuclei

We construct full broad-band models in an analysis of Suzaku observations of nearby Seyfert 1 active galactic nuclei (AGN) (z ≤ 0.2) with exposures >50 ks and with greater than 30 000 counts in order to study their iron line profiles. This results in a sample of 46 objects and 84 observations. After a full modelling of the broad-band Suzaku and Swift-Burst Alert Telescope data (0.6–100 keV), we find complex warm absorption is present in 59 per cent of the objects in this sample which has a significant bearing upon the derived Fe K region parameters. Meanwhile 35 per cent of the 46 objects require some degree of high column density partial coverer in order to fully model the hard X-ray spectrum. We also find that a large number of the objects in the sample (22 per cent) require high velocity, high ionization outflows in the Fe K region resulting from Fe xxv and Fe xxvi. A further four AGN feature highly ionized Fe K absorbers consistent with zero outflow velocity, making a total of 14/46 (30 per cent) AGN in this sample showing evidence for statistically significant absorption in the Fe K region. Narrow Fe Kα emission from distant material at 6.4 keV is found to be almost ubiquitous in these AGN. Examining the 6–7 keV Fe K region we note that narrow emission lines originating from Fe xxv at 6.63–6.70 keV and from Fe xxvi at 6.97 keV are present in 52 and 39 per cent of objects, respectively. Our results suggest statistically significant relativistic Fe Kα emission is detected in 23 of 46 objects (50 per cent) at >99.5 per cent confidence, measuring an average emissivity index of q = 2.4 ± 0.1 and equivalent width  eV using the relline model. When parametrized with a Gaussian we find an average line energy of 6.32 ± 0.04 keV, σwidth = 0.470 ± 0.05 keV and  eV. Where we can place constraints upon the black hole spin parameter a, we do not require a maximally spinning black hole in all cases.

A Suzaku survey of Fe K lines in Seyfert 1 AGN

We construct full broad-band models in an analysis of Suzaku observations of nearby Seyfert 1 active galactic nuclei (AGN) (z ≤ 0.2) with exposures >50 ks and with greater than 30 000 counts in order to study their iron line profiles. This results in a sample of 46 objects and 84 observations. After a full modelling of the broad-band Suzaku and Swift-Burst Alert Telescope data (0.6–100 keV), we find complex warm absorption is present in 59 per cent of the objects in this sample which has a significant bearing upon the derived Fe K region parameters. Meanwhile 35 per cent of the 46 objects require some degree of high column density partial coverer in order to fully model the hard X-ray spectrum. We also find that a large number of the objects in the sample (22 per cent) require high velocity, high ionization outflows in the Fe K region resulting from Fe xxv and Fe xxvi. A further four AGN feature highly ionized Fe K absorbers consistent with zero outflow velocity, making a total of 14/46 (30 per cent) AGN in this sample showing evidence for statistically significant absorption in the Fe K region. Narrow Fe Kα emission from distant material at 6.4 keV is found to be almost ubiquitous in these AGN. Examining the 6–7 keV Fe K region we note that narrow emission lines originating from Fe xxv at 6.63–6.70 keV and from Fe xxvi at 6.97 keV are present in 52 and 39 per cent of objects, respectively. Our results suggest statistically significant relativistic Fe Kα emission is detected in 23 of 46 objects (50 per cent) at >99.5 per cent confidence, measuring an average emissivity index of q = 2.4 ± 0.1 and equivalent width  eV using the relline model. When parametrized with a Gaussian we find an average line energy of 6.32 ± 0.04 keV, σwidth = 0.470 ± 0.05 keV and  eV. Where we can place constraints upon the black hole spin parameter a, we do not require a maximally spinning black hole in all cases.

Contemporaneous Chandra HETG and Suzaku X-ray observations of NGC 4051

We present the results of a deep 300 ks Chandra HETG observation of the highly variable narrow-line Seyfert Type 1 galaxy NGC 4051. The HETG spectrum reveals 28 significant soft X-ray ionised lines in either emission or absorption; primarily originating from H-like and Helike K-shell transitions of O, Ne, Mg and Si (including higher order lines and strong forbidden emission lines from O VII and Ne IX) plus high ionisation L-shell transitions from Fe XVII to Fe XXII and lower ionisation inner-shell lines (e.g. O VI). Modelling the data with XSTAR requires four distinct ionisation zones for the gas, all outflo wing with velocities <1 000 km s 1 . A selection of the strongest emission/absorption lines app ear to be resolved with FWHM of �600 km s 1 . We also present the results from a quasi-simultaneous 350 ks Suzaku observation of NGC 4051 where the XIS spectrum reveals strong evidence for blueshifted absorption lines at �6.8 and �7.1 keV, consistent with previous findings. Modelling with XSTAR suggests that this is the signature of a highly ionised, high vel ocity outflow (log � = 4.1 +0.2 0.1 ; vout � 0.02c) which potentially may have a significant effect on the host g alaxy environment via feedback. Finally, we also simultaneously model the broad-band 2008 XIS+HXD Suzaku data with archival Suzaku data from 2005 when the source was observed to have entered an extended period of low flux in an attempt to analyse the cause of the long-term spectral variability. We find that we can account for this by a llowing for large variations in the normalisation of the intrinsic power-law component which may be interpreted as being due to significant changes in the covering fraction of a Compton-th ick partial-coverer obscuring the central continuum emission.

Evidence for a truncated accretion disc in the low-luminosity Seyfert galaxy, NGC 7213?

We present the broad-band 0.6–150 keV Suzaku and Swift BAT spectra of the low-luminosity Seyfert galaxy, NGC 7213. The time-averaged continuum emission is well fitted by a single power law of photon index � = 1.75, and from consideration of the Fermi flux limit we constrain the high-energy cut-off to be 350 keV < Ecut < 25 MeV. Line emission from both near-neutral iron Kα at 6.39 keV and highly ionized iron, from Fe XXV and Fe XXVI, is strongly detected in the Suzaku spectrum, further confirming the results of previous observations with Chandra and XMM–Newton. We find the centroid energies for the emission from Fe XXV and Fe XXVI to be 6.60 and 6.95 keV respectively, with the latter appearing to be resolved in the Suzaku spectrum. From modelling, we show that the Fe XXV and Fe XXVI emission can result from a highly photoionized plasma, with a column density of NH ∼ 3 × 10 23 cm −2 . A Compton reflection component, e.g. originating from an optically thick accretion disc or a Compton-thick torus, appears either very weak or absent in this active galactic nucleus (AGN), subtending <1 sr to the X-ray source, consistent with previous findings. Indeed, the absence of Compton reflection from either neutral or ionized material coupled with the lack of any relativistic Fe K signatures in the spectrum suggests that an inner, optically thick accretion disc is absent in this source. Instead, the accretion disc could be truncated with the inner regions perhaps replaced by a Compton-thin radiatively inefficient accretion flow (RIAF). Thus, the Fe XXV and Fe XXVI emission could both originate in ionized material perhaps at the transition region between the hot, inner flow and the cold, truncated accretion disc on the order of 10 3 –10 4 gravitational radii from the black hole. The origin for the unresolved neutral Fe Kα emission is then likely to be further out, perhaps originating in the optical broad-line region or a Compton-thin pc-scale torus.

A broad-band X-ray view of the warm absorber in radio-quiet quasar MR 2251−178

We present the analysis of a new broad-band X-ray spectrum (0.6―180.0 keV) of the radio-quiet quasar MR 2251—178 which uses both Suzaku and Swift/Burst Alert Telescope data. In accordance with previous observations, we find that the general continuum can be well described by a power law with Γ = 1.6 and an apparent soft excess below 1 keV. Warm absorption is clearly present, and absorption lines due to the Fe unresolved transition array, Fe L (Fe XXIII-XXIV), S xv and S XVI are detected below 3 keV. At higher energies, Fe K absorption from Fe XXV―XXVI is detected and a relatively weak (EW = 25 +12 ―8 eV) narrow Fe Kα emission line is observed (E = 6.44 ± 0.04 keV) which is well modelled by the presence of a mildly ionized (ξ ≲ 30) reflection component with a low reflection fraction (R < 0.2). At least five ionized absorption components with 10 20 ≲ N H ≲ 10 23 cm ―2 and 0 ≲ logξ/erg cm s ―1 ≲ 4 are required to achieve an adequate spectral fit. Alternatively, we show that the continuum can also be fit if a Γ ∼ 2.0 power law is absorbed by a column of N H ∼ 10 23 cm ―2 which covers ∼30 per cent of the source flux. Independent of which continuum model is adopted, the Fe L and Fe xxv Heα lines are well fit by a single absorber outflowing with υ out ∼ 0.14c. Such an outflow/disc-wind is likely to be substantially clumped (b ∼ 10 ―3 ) in order to not vastly exceed the likely accretion rate of the source.