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We use the Hubble Space Telescope to analyse the extended [O  iii ] 5007 Å emission in seven bright radio-quiet type 1 quasars (QSO1s), focusing on the morphology and physical conditions of their extended Narrow-Line Regions (NLRs). We find NLRs extending 3–9 kpc, with four quasars showing roughly symmetrical structures (⁠|$b/a$| =1.2–1.5) and three displaying asymmetric NLRs (⁠|$b/a$| =2.4–5.6). When included with type 1 and type 2 AGNs from previous studies, the sizes of the extended [O  iii ] regions scale with luminosity as |$R_{\rm [O\,{\rm {\small III}}]}\sim L_{\rm [O\,{\rm {\small III}}]}^{0.5}$|⁠ , consistent with photoionization. However, when analysed separately, type 1s exhibit a steeper slope (⁠|$\gamma _{1}$| = 0.57 |$\pm$| 0.05) compared to type 2 AGNs (⁠|$\gamma _{2}$| = 0.48 |$\pm$| 0.02). We use photoionization modelling to estimate the maximum NLRs sizes, assuming a minimum ionization parameter of log |$(U)=-3$|⁠ , an ionizing luminosity based on the |$L_{\rm [O\,{\rm {\small III}}]}$| -derived bolometric luminosity, and a minimum gas number density |$n_{\rm H}\sim 100$|  cm |$^{-3}$|⁠ , assuming that molecular clouds provide a reservoir for the ionized gas. The derived sizes agree well with direct measurements for a sample of type 2 quasars, but are underestimated for the current sample of QSO1s. A better agreement is obtained for the QSO1s using bolometric luminosities derived from the 5100 Å continuum luminosity. Radial mass profiles for the QSO1s show significant extended mass in all cases, but with less [O  iii ]-emitting gas near the central AGN compared to QSO2s. This may suggest that the QSO1s are in a later evolutionary stage than QSO2s, further past the blow-out stage. [ABSTRACT FROM AUTHOR]

We use cloudy photoionization models to predict the flux profiles for optical/infrared (IR) emission lines that trace the footprint of X-ray gas, such as [Fe  x ] 6375 Å and [Si  x ] 1.43 |$\mu\mathrm{m}$|⁠. These are subset of coronal lines, from ions with ionization potential greater than or equal to that of O  vii , i.e. 138 eV. The footprint lines are formed in gas over the same range in ionization state as the H- and He-like of O and Ne ions, which are also the source of X-ray emission lines. The footprint lines can be detected with optical and IR telescopes, such as the Hubble Space Telescope /STIS and James Webb Space Telescope /NIRSpec, and can potentially be used to measure the kinematics of the extended X-ray emission gas. As a test case, we use the footprints to quantify the properties of the X-ray outflow in the type 1 Seyfert galaxy NGC 4151. To confirm the accuracy of our method, we compare our model predictions to the measured flux from archival STIS spectra and previous ground-based studies, and the results are in good agreement. We also use our X-ray footprint method to predict the mass profile for the X-ray emission-line gas in NGC 4151 and derive a total spatially integrated X-ray mass of |$7.8(\pm 2.1) \times 10^{5}\, {\rm M}_{\odot }$|⁠ , in comparison to |$5.4(\pm 1.1) \times 10^{5}\, {\rm M}_{\odot }$| measured from a Chandra X-ray analysis. Our results indicate that high-ionization footprint emission lines in the optical and near-IR can be used to accurately trace the kinematics and physical conditions of active galactic nucleus-ionized, X-ray emission-line gas. [ABSTRACT FROM AUTHOR]

We present a dynamical study of the narrow-line regions in two nearby type 2 quasars (QSO2s). We construct dynamical models based on detailed photoionization models of the emission-line gas, including the effects of internal dust, to apply to observations of large-scale outflows from these active galactic nuclei (AGNs). We use Mrk 477 and Mrk 34 in order to test our models against recent Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) observations of [O  iii ] emission-line kinematics, since these AGNs possess more energetic outflows than found in Seyfert galaxies. We find that the outflows within 500 pc are consistent with radiative acceleration of dusty gas, however the outflows in Mrk 34 are significantly more extended and may not be directly accelerated by radiation. We characterize the properties of X-ray winds found from the expansion of [O  iii ]-emitting gas close to the black hole. We show that such winds possess the kinetic energy density to disturb [O  iii ] gas at ∼1.8 kpc, and have sufficient energy to entrain the [O  iii ] clouds at ∼1.2 kpc. Assuming that the X-ray wind possesses the same radial mass distribution as the [O  iii ] gas, we find that the peak kinetic luminosity for this wind is 2 per cent of Mrk 34's bolometric luminosity, which is in the 0.5–5 per cent range required by some models for efficient feedback. Our work shows that, although the kinetic luminosity as measured from [O  iii ]-emitting gas is frequently low, X-ray winds may provide more than one order of magnitude higher kinetic power. [ABSTRACT FROM AUTHOR]

We use Hubble Space Telescope /Space Telescope Imaging Spectrograph long-slit G430M and G750M spectra to analyse the extended [O  iii ] λ5007 emission in a sample of 12 nearby (z < 0.12) luminous (L bol > 1.6 × 1045 erg s−1) QSO2s. The purpose of the study is to determine the properties of the mass outflows of ionized gas and their role in active galactic nucleus feedback. We measure fluxes and velocities as functions of radial distances. Using cloudy models and ionizing luminosities derived from [O  iii ] λ5007, we are able to estimate the densities for the emission-line gas. From these results, we derive masses of [O  iii ]-emitting gas, mass outflow rates, kinetic energies, kinetic luminosities, momenta, and momentum flow rates as a function of radial distance for each of the targets. For the sample, masses are several times |$10^{3}$| – |$10^{7}\, {\rm M_{\odot }}$| and peak outflow rates are from 9.3 × 10−3 to |$10.3\, {\rm M_{\odot }}\, {\rm yr^{-1}}$|⁠. The peak kinetic luminosities are (3.4 × 10−8)–(4.9 × 10−4) of the bolometric luminosity, which does not approach the (5.0 × 10−3)–(5.0 × 10−2) range required by some models for efficient feedback. For Mrk 34, which has the largest kinetic luminosity of our sample, in order to produce efficient feedback there would have to be 10 times more [O  iii ]-emitting gas than that we detected at its position of maximum kinetic luminosity. Three targets show extended [O  iii ] emission, but compact outflow regions. This may be due to different mass profiles or different evolutionary histories. [ABSTRACT FROM AUTHOR]

A joint XMM–Newton and NuSTAR observation was conducted for the bright, local Seyfert 1.9 galaxy, NGC 1194. The hard spectral form of this active galactic nucleus (AGN) was modelled using the toroidal reprocessor mytorus. The decoupled model form provides a good description of the spectrum, with reflection arising from gas with a global average column density >4 × 1024 cm−2 and transmission of the continuum through an order-of-magnitude lower column. In this model, the reflection strength is a factor of ∼3 higher than expected from a simple torus. Such a result may indicate that much of the intrinsic X-ray continuum is hidden from view. An alternative model is that of a patchy torus, where 85 per cent of sightlines are obscured by Compton-thick gas and the remaining 15 per cent by Compton-thin gas. The patchy torus model is based on a solar abundance of Fe and is consistent with X-ray partial-covering results found in other AGN. That a patchy torus model would relieve the issue with the strength of the reflection signature is not an intuitive result: such an insight regarding the geometry of the global reprocessing gas could not have been obtained using ad hoc model components to describe the spectral form. [ABSTRACT FROM AUTHOR]

We have analysed Chandra /High Energy Transmission Gratings spectra of the X-ray emission line gas in the Seyfert galaxy NGC 4151. The zeroth-order spectral images show extended H- and He-like O and Ne, up to a distance r ∼ 200 pc from the nucleus. Using the first-order spectra, we measure an average line velocity ∼−230 km s−1, suggesting significant outflow of X-ray gas. We generated cloudy photoionization models to fit the first-order spectra; the fit required three distinct emission line components. To estimate the total mass of ionized gas and the mass outflow rates, we applied the model parameters to fit the zeroth-order emission line profiles of Ne  ix and Ne  x. We determined the total mass of ≈5.4 × 105 M⊙. Assuming the same kinematic profile as that for the [O  iii ] gas, derived from our analysis of Hubble Space Telescope /Space Telescope Imaging Spectrograph spectra, the peak X-ray mass outflow rate was ≈1.8 M⊙ yr−1, at r ∼ 150 pc. The total mass and mass outflow rates are similar to those determined using [O  iii ], implying that the X-ray gas is a major outflow component. However, unlike the optical outflows, the X-ray outflow rate does not drop off at r > 100 pc, which suggests that it may have a greater impact on the host galaxy. [ABSTRACT FROM AUTHOR]

We have analyzed Chandra/High Energy Transmission Grating spectra of the X-ray emission line gas in the Seyfert galaxy NGC 4151. The zeroth-order spectral images show extended H- and He-like O and Ne, up to a distance r ˜ 200 pc from the nucleus. Using the 1st-order spectra, we measure an average line velocity ˜230 km s–1, suggesting significant outflow of X-ray gas. We generated Cloudy photoionization models to fit the 1st-order spectra; the fit required three distinct emission-line components. To estimate the total mass of ionized gas (M) and the mass outflow rates, we applied the model parameters to fit the zeroth-order emission-line profiles of Ne IX and Ne X. We determined an M ≍ 5.4 × 105Mʘ. Assuming the same kinematic profile as that for the [O III] gas, derived from our analysis of Hubble Space Telescope/Space Telescope Imaging Spectrograph spectra, the peak X-ray mass outflow rate is approximately 1.8 Mʘ yr–1, at r ˜ 150 pc. The total mass and mass outflow rates are similar to those determined using [O III], implying that the X-ray gas is a major outflow component. However, unlike the optical outflows, the X-ray emitting mass outflow rate does not drop off at r > 100pc, which suggests that it may have a greater impact on the host galaxy. [ABSTRACT FROM AUTHOR]

NGC 3227 exhibits rapid flux and spectral variability in the X-ray band. To understand this behaviour, we conducted a coordinated observing campaign using 320 ks of XMM–Newton exposures together with 160 ks of overlapping NuSTAR observations, spanning a month. Here, we present a rapid variability event that occurs toward the end of the campaign. The spectral hardening event is accompanied by a change in the depth of an unresolved transition array (UTA), whose time-dependent behaviour is resolved using the RGS data. This UTA fingerprint allows us to identify this as a transit event, where a clump of gas having |$N_\mathrm{ H} \sim 5 \times 10^{22}\, {\rm atoms\, cm^{-2}}$|⁠, log ξ ∼ 2 occults |${\sim } 60{{\ \rm per\ cent}}$| of the continuum photons over the course of approximately a day. This occulting gas is likely associated with clouds in the inner broad-line region. An additional zone of gas with lower column and higher ionization, matches the outflow velocity of the variable zone, and may represent transmission through the cloud limb. [ABSTRACT FROM AUTHOR]

We present the discovery of a new candidate for a fast disc wind, in the nearby Seyfert 2 galaxy MCG-03-58-007. This wind is discovered in a deep Suzaku observation that was performed in 2010. Overall the X-ray spectrum of MCG-03-58-007 is highly absorbed by a neutral column density of N H ∼1023 cm−2, in agreement with the optical classification as a type 2 active galactic nucleus. In addition, this observation unveiled the presence of two deep absorption troughs at E = 7.4 ± 0.1 and 8.5 ± 0.2 keV. If associated with blueshifted Fe  xxvi, these features can be explained with the presence of two highly ionized (log ξ/erg cm s−1 ∼5.5) and high column density (N H ∼ 5–8 × 1023 cm−2) outflowing absorbers with v out1 ∼ −0.1 c and v out2 ∼ −0.2 c. The disc wind detected during this observation is most likely launched from within a few hundreds gravitational radii from the central black and has a kinetic output that matches the prescription for significant feedback. The presence of the lower velocity component of the disc wind is independently confirmed by the analysis of a follow-up XMM–Newton and NuSTAR observation. A faster (v out ∼ −0.35 c) component of the wind is also seen in this second observation. During this observation we also witnessed an occultation event lasting Δ t ∼ 120 ks, which we ascribe to an increase of the opacity of the disc wind (Δ N H ∼ 1.4 × 1024 cm−2). Our interpretation is that the slow zone (v out ∼ −0.1 c) of the wind is the most stable but inhomogeneous component, while the faster zones could be associated with two different inner streamlines of the wind. [ABSTRACT FROM AUTHOR]

A NuSTAR/Swift observation of the luminous Seyfert 1 galaxy 1H 0419-577 taken during 2015 reveals one of the most extreme high-energy cut-offs observed to date from an AGN - an origin due to thermal Comptonization would imply a remarkably low coronal temperature kT ~ 15 keV. The low-energy peak of the spectrum in the hard X-ray NuSTAR band, which peaks before the expected onset of a Compton hump, rules out strong reflection as the origin of the hard excess in this AGN. We show the origin of the high-energy rollover is likely due to a combination of both thermal Comptonization and an intrinsically steeper continuum, which is modified by absorption at lower energies. Furthermore, modelling the broad-band XUV continuum shape as a colour-corrected accretion disc, requires the presence of a variable warm absorber to explain all flux and spectral states of the source, consistent with the previous work on this AGN. While absorber variations produce marked spectral variability in this AGN, consideration of all flux states allows us to isolate a colourless component of variability that may arise from changes in the inner accretion flow, typically at around 10 rg. [ABSTRACT FROM AUTHOR]

We present an analysis of a 190 ks (net exposure) Suzaku observation, carried out in 2007, of the nearby (z = 0.184) luminous (Lbol ~ 1047 erg s-1) quasar PDS 456. In this observation, the intrinsically steep bare continuum is revealed compared to subsequent observations, carried out in 2011 and 2013, where the source is fainter, harder and more absorbed. We detected two pairs of prominent hard and soft flares, restricted to the first and second halves of the observation, respectively. The flares occur on time-scales of the order of ~50 ks, which is equivalent to a light-crossing distance of ~10 Rg in PDS 456. From the spectral variability observed during the flares, we find that the continuum changes appear to be dominated by two components: (i) a variable soft component (<2 keV), which may be related to the Comptonized tail of the disc emission, and (ii) a variable hard power-law component (>2 keV). The photon index of the latter power-law component appears to respond to changes in the soft band flux, increasing during the soft X-ray flares. Here, the softening of the spectra, observed during the flares, may be due to Compton cooling of the disc corona induced by the increased soft X-ray photon seed flux. In contrast, we rule out partial covering absorption as the physical mechanism behind the observed short time-scale spectral variability, as the time-scales are likely too short to be accounted for by absorption variability. [ABSTRACT FROM AUTHOR]

Fairall 9 is one of several type 1 active galactic nuclei for which it has been claimed that the angular momentum (or spin) of the supermassive black hole can be robustly measured, using the Fe Kα emission line and Compton-reflection continuum in the X-ray spectrum. The method rests upon the interpretation of the Fe Kα line profile and associated Compton-reflection continuum in terms of relativistic broadening in the strong gravity regime in the innermost regions of an accretion disc, within a few gravitational radii of the black hole. Here, we re-examine a Suzaku X-ray spectrum of Fairall 9 and show that a face-on toroidal X-ray reprocessor model involving only non-relativistic and mundane physics provides an excellent fit to the data. The Fe Kα line emission and Compton-reflection continuum are calculated self-consistently, the iron abundance is solar, and an equatorial column density of ∼ 1024 cm− 2 is inferred. In this scenario, neither the Fe Kα line nor the Compton-reflection continuum provides any information on the black hole spin. Whereas previous analyses have assumed an infinite column density for the distant-matter reprocessor, the shape of the reflection spectrum from matter with a finite column density eliminates the need for a relativistically broadened Fe Kα line. We find a 90 per cent confidence range in the Fe Kα line full width at half-maximum of 1895–6205 km s− 1, corresponding to a distance of ∼3100 to 33 380 gravitational radii from the black hole, or 0.015–0.49 pc for a black hole mass of ∼1–3 × 108 M⊙. [ABSTRACT FROM AUTHOR]

Mkn 3 is a Seyfert 2 galaxy that is widely regarded as an exemplary Compton-thick Active Galactic Nucleus (AGN). We study the Suzaku X-ray spectrum using models of the X-ray reprocessor that self-consistently account for the Fe Kα fluorescent emission line and the associated Compton-scattered, or reflection, continuum. We find a solution in which the average global column density, 0.234-0.010+0.012 × 1024 cm-2, is very different to the line-of-sight column density, 0.902-0.013+0.012 × 1024 cm-2. The global column density is ~5 times smaller than that required for the matter distribution to be Compton thick. Our model accounts for the profiles of the Fe Kα and Fe Kβ lines, and the Fe K edge remarkably well, with a solar abundance of Fe. The matter distribution could consist of a clumpy medium with a line-of-sight column density higher than the global average. A uniform, spherically symmetric distribution alone cannot simultaneously produce the correct fluorescent line spectrum and reflection continuum. Previous works on Mkn 3, and other AGN, that assumed a reflection continuum from matter with an infinite column density could therefore lead to erroneous or 'puzzling' conclusions if the matter out of the line of sight is really Compton thin. Whereas studies of samples of AGN have generally only probed the line-of-sight column density, with simplistic, one-dimensional models, it is important now to establish the global column densities in AGN. It is the global properties that affect the energy budget in terms of reprocessing of X-rays into infrared emission, and that constrain population synthesis models of the cosmic X-ray background. [ABSTRACT FROM AUTHOR]

Ongoing studies with XMM-Newton have shown that powerful accretion disc winds, as revealed through highly ionized Fe K-shell absorption at E = 6.7 keV, are present in a significant fraction of active galactic nuclei (AGNs) in the local Universe (Tombesi et al. 2010a). In Gofford et al., we analysed a sample of 51 Suzaku-observed AGNs and independently detected Fe K absorption in ~40 per cent of the sample, and we measured the properties of the absorbing gas. In this work, we build upon these results to consider the properties of the associated wind. On average, the fast winds (vw > 0.01c) are located ~ 1015-18 cm (typically ~102-4 rs) from their black hole, their mass outflow rates are of the order of w>~0.01-1 M⊙ yr-1 or ~(0.01-1)MEdd and kinetic power is constrained to w> ~ 1043-45 erg s-1, equivalent to ~(0.1-10 per cent)LEdd. We find a fundamental correlation between the source bolometric luminosity and the wind velocity, with vw∝Lbolα and α=0.4-0.2+0.3 (90 per cent confidence), which indicates that more luminous AGN tend to harbour faster Fe K winds. The mass outflow rate Mw, kinetic power Lw and momentum flux pw of the winds are also consequently correlated with Lbol, such that more massive and more energetic winds are present in more luminous AGN. We investigate these properties in the framework of a continuum-driven wind, showing that the observed relationships are broadly consistent with a wind being accelerated by continuum-scattering. We find that, globally, a significant fraction (~85 per cent) of the sample can plausibly exceed the Lw/Lbol ~ 0.5 per cent threshold thought necessary for feedback, while 45 per cent may also exceed the less conservative ~5 per cent of Lbol threshold as well. This suggests that the winds may be energetically significant for AGN-host-galaxy feedback processes. [ABSTRACT FROM AUTHOR]

Context. Arakelian 564 (Ark 564, z = 0.0247) is an X-ray-bright narrow-line Seyfert 1 galaxy. By using advanced X-ray timing techniques, an excess of "delayed" emission in the hard X-ray band (4-7.5 keV) following about 1000 s after "flaring" light in the soft X-ray band (0.4-1 keV) was recently detected. Aims. We report on the X-ray spectral analysis of eight XMM-Newton and one Suzaku observation of Ark 564. Our aim is to characterise the X-ray spectral properties of the source in the light of these recently reported results. Methods. High-resolution spectroscopy was performed with the RGS in the soft X-ray band, while broad-band spectroscopy was performed with the EPIC-pn and XIS/PIN instruments. We analysed time-averaged, flux-selected, and time-resolved spectra. Results. Despite the strong variability in flux during our observational campaign, the broad-band spectral shape of Ark 564 does not vary dramatically and can be reproduced either by a superposition of a power law and a blackbody emission or by a Comptonized power-law emission model. High-resolution spectroscopy revealed ionised gas along the line of sight at the systemic redshift of the source, with a low column density (NH ~ 1021 cm-2) and a range of ionisation states (-0.8 < log(ξ/erg cms-1) < 2.4). Broad-band spectroscopy revealed a very steep intrinsic continuum (photon index Γ ~ 2.6) and a rather weak emission feature in the iron K band (EW ~ 150 eV); modelling this feature with a reflection component requires highly ionised gas, log(ξ/erg cms-1) > 3.5. A reflection-dominated or an absorption-dominated model are similarly able to well reproduce the time-averaged data from a statistical point of view, in both cases requiring contrived geometries and/or unlikely physical parameters. Finally, through time-resolved analysis we spectroscopically identified the "delayed" emission as a spectral hardening above ~4 keV; the most likely interpretation for this component is a reprocessing of the "flaring" light by gas located at 10-100 rg from the central supermassive black hole that is so hot that it can Compton-upscatter the flaring intrinsic continuum emission. [ABSTRACT FROM AUTHOR]

We present a comparison of two Suzaku X-ray observations of the nearby (z = 0.184), luminous (Lbol ∼ 1047 erg s–1) type I quasar, PDS 456. A new 125 ks Suzaku observation in 2011 caught the quasar during a period of low X-ray flux and with a hard X-ray spectrum, in contrast with a previous 190 ks Suzaku observation in 2007 when the quasar appeared brighter and had a steep (Γ > 2) X-ray spectrum. The 2011 X-ray spectrum contains a pronounced trough near 9 keV in the quasar rest frame, which can be modeled with blueshifted iron K-shell absorption, most likely from the He- and H-like transitions of iron. The absorption trough is observed at a similar rest-frame energy as in the earlier 2007 observation, which appears to confirm the existence of a persistent high-velocity wind in PDS 456, at an outflow velocity of 0.25-0.30c. The spectral variability between 2007 and 2011 can be accounted for by variations in a partial covering absorber, increasing in covering fraction from the brighter 2007 observation to the hard and faint 2011 observation. Overall, the low-flux 2011 observation can be explained if PDS 456 is observed at relatively low inclination angles through a Compton-thick wind, originating from the accretion disk, which significantly attenuates the X-ray flux from the quasar. [ABSTRACT FROM AUTHOR]

High resolution X-ray spectroscopy of the warm absorber in a nearby quasar, MR 2251-178 (z = 0.06398), is presented. The observations were carried out in 2011 using the Chandra High Energy Transmission Grating (HETG) and the XMM-Newton Reflection Grating Spectrometer, with net exposure times of approximately 400 ks each. A multitude of absorption lines from C to Fe are detected, revealing at least three warm absorbing components ranging in ionization parameter from log (ξ/erg cm s–1) = 1-3 with outflow velocities ≲ 500 km s–1. The lowest ionization absorber appears to vary between the Chandra and XMM-Newton observations, which implies a radial distance of between 9 and 17 pc from the black hole. Several broad soft X-ray emission lines are strongly detected, most notably from He-like oxygen, with FWHM velocity widths of up to 10,000 km s–1, consistent with an origin from broad-line region (BLR) clouds. In addition to the warm absorber, gas partially covering the line of sight to the quasar appears to be present, with a typical column density of NH = 1023 cm–2. We suggest that the partial covering absorber may arise from the same BLR clouds responsible for the broad soft X-ray emission lines. Finally, the presence of a highly ionized outflow in the iron K band from both the 2002 and 2011 Chandra HETG observations appears to be confirmed, which has an outflow velocity of –15600 ± 2400 km s–1. However, a partial covering origin for the iron K absorption cannot be excluded, resulting from low ionization material with little or no outflow velocity. [ABSTRACT FROM AUTHOR]

This work presents an integrated experimental and modeling approach for examining the deformation of a pure nickel polycrystal utilizing micromechanical testing and a crystal-based elasto-viscoplastic finite-element model (CPFEM). The objective is to study the influence of microstructure on the heterogeneous deformation in polycrystalline materials, and to utilize a modeling framework to explore aspects of the deformation that are difficult or impossible to measure experimentally. To accomplish this, a microtension specimen containing 259 grains was created from a pure nickel foil material and deformed in uniaxial tension. After the deformation, the specimen was destructively serial sectioned in concert with electron back scattering diffraction, and these data were used to instantiate a CPFEM simulation. The material parameters in the CPFEM model were calibrated by matching the experimental macroscopic stress-strain response of the microtension specimen, and then the simulation results were compared with experimental surface deformations measured with digital image correlation. After validating the simulation results by comparing measured and predicted surface strain distributions, a parametric study of the influence of both crystallographic texture and grain morphology is presented to better understand the influence of microstructure on the development of heterogeneous deformation in the pure nickel polycrystalline material. [ABSTRACT FROM AUTHOR]

ABSTRACT Ultraviolet and X-ray observations show evidence of outflowing gas around many active galactic nuclei. It has been proposed that some of these outflows are driven off gas infalling towards the central supermassive black hole. We perform radiative transfer calculations to compute the gas ionization state and the emergent X-ray spectra for both two- and three-dimensional (3D) hydrodynamical simulations of this outflow-from-inflow scenario. By comparison with observations, our results can be used to test the theoretical models and guide future numerical simulations. We predict both absorption and emission features, most of which are formed in a polar funnel of relatively dense (10−20-10−18 g cm−3) outflowing gas. This outflow causes strong absorption for observer orientation angles of ≲35°. Particularly in 3D, the strength of this absorption varies significantly for different lines of sight owing to the fragmentary structure of the gas flow. Although infalling material occupies a large fraction of the simulation volume, we do not find that it imprints strong absorption features in the X-ray spectra since the ionization state is predicted to be very high. Thus, an absence of observed inflow absorption features does not exclude the models. The main spectroscopic consequence of the infalling gas is a Compton-scattered continuum component that partially re-fills the absorption features caused by the outflowing polar funnel. Fluorescence and scattering in the outflow are predicted to give rise to several emission features including a multicomponent Fe Kα emission complex for all observer orientations. For the hydrodynamical simulations considered, we predict both ionization states and column densities for the outflowing gas that are too high to be quantitatively consistent with well-observed X-ray absorption systems. Nevertheless, our results are qualitatively encouraging and further exploration of the model parameter space is warranted. Higher resolution hydrodynamic simulations are needed to determine whether the outflows fragment on scales unresolved in our current study, which may yield the denser lower ionization material that could reconcile the models and the observations. [ABSTRACT FROM AUTHOR]

BSTRACT [ABSTRACT FROM AUTHOR]

We present the results of a deep 300 ks Chandra High Energy Transmission Grating (HETG) observation of the highly variable narrow-line Seyfert Type 1 galaxy NGC 4051. The HETG spectrum reveals 28 significant soft X-ray ionized lines in either emission or absorption; primarily originating from H-like and He-like K-shell transitions of O, Ne, Mg and Si (including higher order lines and strong forbidden emission lines from O and Ne ) plus high-ionization L-shell transitions from Fe to Fe and lower ionization inner-shell lines (e.g. O ). Modelling the data with requires four distinct ionization zones for the gas, all outflowing with velocities 1000 km s. A selection of the strongest emission/absorption lines appear to be resolved with full width at half-maximum (FWHM) of 600 km s. We also present the results from a quasi-simultaneous 350 ks Suzaku observation of NGC 4051 where the X-ray Imaging Spectrometer (XIS) spectrum reveals strong evidence for blueshifted absorption lines at 6.8 and 7.1 keV, consistent with previous findings. Modelling with suggests that this is the signature of a highly ionized, high-velocity outflow (log ; ) which potentially may have a significant effect on the host galaxy environment via feedback. Finally, we also simultaneously model the broad-band 2008 XIS+HXD (Hard X-ray Detector) 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 allowing for large variations in the normalization of the intrinsic power-law component which may be interpreted as being due to significant changes in the covering fraction of a Compton-thick partial-coverer obscuring the central continuum emission. [ABSTRACT FROM AUTHOR]

The narrow-line Seyfert 1 galaxy 1H 495 has previously been identified as showing time lags between flux variations in the soft-energy (0.3-1 keV) and medium-energy (1-4 keV) X-ray bands that oscillate between positive and negative values as a function of the frequency of the mode of variation. Here we measure and analyse the lags also between a harder X-ray band (4-7.5 keV) and the soft and medium bands, using existing XMM-Newton data, and demonstrate that the entire spectrum of lags, considering both the full energy range, 0.3-7.5 keV, and the full frequency range, Hz, are inconsistent with previous claims of arising as reverberation associated with the inner accretion disc. Instead we demonstrate that a simple reverberation model, in which scattering or reflection is present in all X-ray bands, explains the full set of lags without requiring any ad hoc explanation for the time lag sign changes. The range of time delays required to explain the observed lags extends up to about 1800 s in the hard band. The results are consistent with reverberation caused by scattering of X-rays passing through an absorbing medium whose opacity decreases with increasing energy and that partially covers the source. A high covering factor of absorbing and scattering circumnuclear material is inferred. [ABSTRACT FROM AUTHOR]

We perform multidimensional radiative transfer simulations to compute spectra for a hydrodynamical simulation of a line-driven accretion disc wind from an active galactic nucleus. The synthetic spectra confirm expectations from parametrized models that a disc wind can imprint a wide variety of spectroscopic signatures including narrow absorption lines, broad emission lines and a Compton hump. The formation of these features is complex with contributions originating from many of the different structures present in the hydrodynamical simulation. In particular, spectral features are shaped both by gas in a successfully launched outflow and in complex flows where material is lifted out of the disc plane but ultimately falls back. We also confirm that the strong Fe Kα line can develop a weak, red-skewed line wing as a result of Compton scattering in the outflow. In addition, we demonstrate that X-ray radiation scattered and reprocessed in the flow has a pivotal part in both the spectrum formation and determining the ionization conditions in the wind. We find that scattered radiation is rather effective in ionizing gas which is shielded from direct irradiation from the central source. This effect likely makes the successful launching of a massive disc wind somewhat more challenging and should be considered in future wind simulations. [ABSTRACT FROM AUTHOR]

ABSTRACT 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 Γ= 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 × 1023 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 103-104 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. [ABSTRACT FROM AUTHOR]

Long-exposure Suzaku X-ray observations of the nearby active galaxy NGC 4051 from 2005 and 2008 are analysed, in an attempt to reach a self-consistent understanding of both the spectral variability on long time-scales and the broad-band variability at high time resolution. The techniques of principal components analysis and a maximum likelihood method of power spectrum analysis are used. In common with other type I active galactic nuclei (AGN), the spectral variability is dominated by a varying-normalization power-law component together with a quasi-steady, hard-spectrum offset component that contains Fe K atomic features. NGC 4051 displays a strong excess over a power law at energies of above 20 keV, some fraction of which also appears to vary with the power-law continuum. The fast time-scale power spectrum has a shape generally consistent with previous determinations, with the previously known dependence on broad-band photon energy, but in the new data significant differences are found between the low and high flux states of the source, demonstrating that the power spectrum is non-stationary. Frequency-dependent time lags between the hard and soft bands of up to s are measured. The existence of the observed time lags excludes the possibility that the hard spectral component originates as reflection from the inner accretion disc. We instead show that the time lags and their frequency and energy dependence may be explained simply by the effects of reverberation in the hard band, caused by reflection from a thick shell of material with maximum lags of about 10 000 s. If the reflecting material surrounds the AGN, it extends to a distance of about cm, 600 gravitational radii, from the illuminating source and the global covering factor is , confirming previous suggestions that type I AGN have high covering factors of absorbing and reflecting material. Given the spectral and timing similarities with other type I AGN, we infer that this source structure is common in the type I population. [ABSTRACT FROM AUTHOR]

The absolute luminosity of the Fe Kα emission line from matter illuminated by X-rays in astrophysical sources is non-trivial to calculate except when the line-emitting medium is optically thin to absorption and scattering. We characterize the Fe Kα line flux using a dimensionless efficiency, defined as the fraction of continuum photons above the Fe K shell absorption edge threshold energy that appear in the line. The optically thin approximation begins to break down even for column densities as small as . We show how to obtain reliable estimates of the Fe Kα line efficiency in the case of cold, neutral matter, even for the Compton-thick regime. We find that, regardless of geometry and covering factor, the largest Fe Kα line efficiency is attained well before the medium becomes Compton-thick. For cosmic elemental abundances it is difficult to achieve an efficiency higher than a few per cent under the most favourable conditions and lines of sight. For a given geometry, Compton-thick lines-of-sight may have Fe Kα line efficiencies that are orders of magnitude less than the maximum possible for that geometry. Configurations that allow unobscured views of a Compton-thick reflecting surface are capable of yielding the highest efficiencies. Our results can be used to estimate the predicted flux of the narrow Fe Kα line at from absorption models in active galactic nucleus (AGN). In particular we show that contrary to a recent claim in the literature, absorption-dominated models for the relativistic Fe Kα emission line in 6-30-15 do not overpredict the narrow Fe Kα line for any column density or covering factor. [ABSTRACT FROM AUTHOR]

MCG–6-30-15 is the archetypal example of a type I active galaxy showing broad ‘red-wing’ emission in its X-ray spectrum at energies below the 6.4 keV Fe Kα emission line and a continuum excess above 20 keV. Miller et al. showed that these spectral features could be caused by clumpy absorbing material, but Reynolds et al. have argued that the observed Fe Kα line luminosity is inconsistent with this explanation unless the global covering factor of the absorber(s) is very low. However, the Reynolds et al. calculation effectively considers the only source of opacity to be the Fe K bound–free transition and neglects the opacity at the line energy: correction to realistic opacity decreases the predicted line flux by a large factor. We also discuss the interpretation of the covering factor and the possible effect of occultation by the accretion disc. Finally, we consider a model for MCG–6-30-15 dominated by clumpy absorption, which is consistent with a global covering factor of 0.45, although models that include the effects of Compton scattering are required to reach a full understanding. Variations in covering fraction may dominate the observed X-ray spectral variability. [ABSTRACT FROM AUTHOR]

We use a multidimensional Monte Carlo code to compute X-ray spectra for a variety of active galactic nucleus (AGN) disc–wind outflow geometries. We focus on the formation of blueshifted absorption features in the Fe K band and show that line features similar to those which have been reported in observations are often produced for lines of sight through disc–wind geometries. We also discuss the formation of other spectral features in highly ionized outflows. In particular, we show that, for sufficiently high wind densities, moderately strong Fe K emission lines can form and that electron scattering in the flow may cause these lines to develop extended red wings. We illustrate the potential relevance of such models to the interpretation of real X-ray data by comparison with observations of a well-known AGN, Mrk 766. [ABSTRACT FROM AUTHOR]

We compute Fourier-resolved X-ray spectra of the Seyfert 1 Markarian 766 to study the shape of the variable components contributing to the 0.3–10 keV energy spectrum and their time-scale dependence. The fractional variability spectra peak at 1–3 keV, as in other Seyfert 1 galaxies, consistent with either a constant contribution from a soft excess component below 1 keV and Compton reflection component above 2 keV or variable warm absorption enhancing the variability in the 1–3 keV range. The rms spectra, which show the shape of the variable components only, are well described by a single power law with an absorption feature around 0.7 keV, which gives it an apparent soft excess. This spectral shape can be produced by a power law varying in normalization, affected by an approximately constant (within each orbit) warm absorber, with parameters similar to those found by Turner et al. for the warm-absorber layer covering all spectral components in their scattering scenario . The total soft excess in the average spectrum can therefore be produced by a combination of constant warm absorption on the power-law plus an additional less variable component. On shorter time-scales, the rms spectrum hardens and this evolution is well described by a change in power-law slope, while the absorption parameters remain the same. The frequency dependence of the rms spectra can be interpreted as variability arising from propagating fluctuations through an extended emitting region, whose emitted spectrum is a power law that hardens towards the centre. This scenario reduces the short time-scale variability of lower energy bands making the variable spectrum harder on shorter time-scales and at the same time explains the hard lags found in these data by Markowitz et al. [ABSTRACT FROM AUTHOR]

A methodology for incorporating a description of material structure into a finite element formulation is presented. This work describes an experiment/simulation - based methodology for characterizing attributes of material structure, and then incorporating those attributes into a modeling framework. The modeling framework was used to study the development of deformation induced surface roughening in thin sheets mnachined from AA 7050 thick plate. Predicting this roughening phenomenon necessitates the quantification and representation of material structure and processes that exist over several size scales. Electron backscatter diffraction experiments were used for material structure characterization, which included crystallographic texture, distributions in grain sizes, and a distribution in intragrain mnisorientation. These distributions in structure were incorporated in digital micro structures which represented virtual specimens composed of finite element-discretized crystals. A continuum slip-polycrystal plasticity model was coupled with the digital microstructures to study the differences in roughening seen in specimens deformed along the rolling direction and transverse direction of the plate material. The success of these simulations build additional insight into how to incorporate material structure into deformation simulations, and build representative virtual specimens that can be used to study the complicated processes that underlie deformation mechanics in polycrystalline materials. [ABSTRACT FROM AUTHOR]

We have investigated the relationship between the X-ray variability amplitude and black hole mass for a sample of 46 radio-quiet active galactic nuclei observed byASCA. 33 of the objects in our sample exhibited significant variability over a time-scale of∼40 ks. We determined the normalized excess variance in the 2–10 keV light curves of these objects and found a significant anticorrelation between excess variance and black hole mass. Unlike most previous studies, we have quantified the variability using nearly the same time-scale for all objects. Moreover, we provide a prescription for estimating the uncertainties in variance which accounts both for measurement uncertainties and for the stochastic nature of the variability. We also present an analytical method to predict the excess variance from a model power spectrum accounting for binning, sampling and windowing effects. Using this, we modelled the variance–mass relation assuming all objects have a universal twice-broken power spectrum, with the position of the breaks being dependent on mass. This accounts for the general form of the variance–mass relationship but is formally a poor fit and there is considerable scatter. We investigated this scatter as a function of the X-ray photon index, luminosity and Eddington ratio. After accounting for the primary dependence of excess variance on mass, we find no significant correlation with either luminosity or X-ray spectral slope. We do find ananticorrelationbetween excess variance and the Eddington ratio, although this relation might be an artefact owing to the uncertainties in the mass measurements. It remains to be established that enhanced X-ray variability is a property of objects with steep X-ray slopes or large Eddington ratios. Narrow-line Seyfert 1 galaxies, in particular, are consistent with being more variable than their broad-line counterparts solely because they tend to have smaller masses. [ABSTRACT FROM AUTHOR]

This paper describes how performance measures were selected and then implemented in two small to medium size enterprises (SMEs) in Central Scotland. It then goes on to consider the impact of these measures on the performance of those businesses using data generated from an action research approach. A review of academic literature on the barriers to implementation of performance measurement systems in general, and those specifically relating to SMEs, suggested that considerable difficulties can be found in implementing performance measures. These perceived difficulties are considered and discussed in relation to the SMEs in question and the approaches used to minimize and overcome them are described. A systematic approach that is well resourced and focused on measuring variation in performance of entire ‘operate’ processes during execution is found to enable business improvement activity. The impact of using this approach on operations management strategy in each SME is reported. The research suggests that implementation of performance measures in an SME will have considerable impact on business performance if the process for implementation is well structured, resourced and focused on improving the capability of ‘operate’ processes. [ABSTRACT FROM AUTHOR]