Kinematics from spectral lines for AGN outflows based on time-independent radiation-driven wind theory (original) (raw)
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THE RISE OF AN IONIZED WIND IN THE NARROW-LINE SEYFERT 1 GALAXY Mrk 335 OBSERVED BYXMM-NEWTONANDHST
The Astrophysical Journal, 2013
We present the discovery of an outflowing ionized wind in the Seyfert 1 galaxy Mrk 335. Despite having been extensively observed by most of the largest X-ray observatories in the last decade, this bright source was not known to host warm absorber gas until recent XMM-Newton observations in combination with a long-term Swift monitoring program have shown extreme flux and spectral variability. High-resolution spectra obtained by the XMM-Newton Reflection Grating Spectrometer (RGS) detector reveal that the wind consists of three distinct ionization components, all outflowing at a velocity of ∼5000 km s −1. This wind is clearly revealed when the source is observed at an intermediate flux state (2-5 × 10 −12 erg cm −2 s −1). The analysis of multi-epoch RGS spectra allowed us to compare the absorber properties at three very different flux states of the source. No correlation between the warm absorber variability and the X-ray flux has been determined. The two higher ionization components of the gas (log ξ ∼ 2.3 and 3.3) may be consistent with photoionization equilibrium, but we can exclude this for the only ionization component that is consistently present in all flux states (log ξ ∼ 1.8). We have included archival, non-simultaneous UV data from Hubble Space Telescope (FOS, STIS, COS) with the aim of searching for any signature of absorption in this source that so far was known for being absorption-free in the UV band. In the Cosmic Origins Spectrograph (COS) spectra obtained a few months after the X-ray observations, we found broad absorption in C iv lines intrinsic to the active galactic nucleus and blueshifted by a velocity roughly comparable to the X-ray outflow. The global behavior of the gas in both bands can be explained by variation of the covering factor and/or column density, possibly due to transverse motion of absorbing clouds moving out of the line of sight at broad line region scale.
The X-ray evolution of inflows and outflows in active galactic nuclei
2010
The evolution 2 of the space density of AGNs might have spectral counterparts which could be observable in X-rays. The main objective of this thesis is to study the spectral properties of AGNs in X-rays in order to increase our current knowledge of AGN evolution. We are especially interested in high redshift AGNs with z 1.0, because the analysis of their spectra may indicate what parameters show evolutionary trends and provide insight as to which physical processes are markers of AGN evolution. The thesis begins with an introduction and review of the scientific topics that are pursued in this study. The core of my research is presented in chapters 2, 3 and 4 of the thesis. In chapter 2, we present results from a statistical analysis of 173 bright radioquiet AGNs selected from the Chandra Deep Field-North and Chandra Deep Field-South surveys (hereafter, CDFs) in the redshift range of 0.1 z 4. We find that the Xray power-law photon index (Γ) of radio-quiet AGNs is correlated with their 2-10 keV rest-frame X-ray luminosity (L X) at the > 99.5% confidence level in two redshift bins, 0.3 z 0.96, and 1.5 z 3.3 and is slightly less significant in the redshift bin 0.96 z 1.5. The X-ray spectral slope steepens as the X-ray luminosity increases for AGNs in the luminosity range 10 42 to 10 45 erg s −1. Combining our results from the CDFs with those from previous studies in the redshift range 1.5 z 3.3, we find that the Γ − L X correlation has a null-hypothesis probability of 1.6 ×10 −9. We investigate the redshift evolution of the correlation between the power-law photon index and the hard X-ray luminosity and find that the slope and offset of a linear fit to the correlation change significantly (at the > 99.9% confidence level) between redshift bins of 0.3 z 0.96 and 1.5 z 3.3. We explore physical scenarios explaining the origin of this correlation and its possible evolution with redshift in the context of steady corona models focusing on its dependency on variations of the properties of the hot corona with redshift. In chapter 3, we present results from three Suzaku observations of the z = 3.91 gravitationally lensed broad absorption line quasar APM 08279+5255. We detect strong and broad absorption at rest-frame energies of 2 keV (low-energy) and 7-12 keV (highenergy). The detection of these features confirms the results of previous long-exposure (80-90 ks) Chandra and XMM-Newton observations. The low and high-energy absorption is detected in both the back-illuminated (BI) and front-illuminated (FI) Suzaku XIS spectra (with an F-test significance of 99%). We interpret the low-energy absorption as arising from a low-ionization absorber with log (N H /cm −2) ∼ 23 and the high-energy absorption as due to lines arising from highly ionized (2.75 log ξ 4.0; where ξ is the ionization parameter) iron in a near-relativistic outflowing wind. Assuming this interpretation we find that the velocities in the outflow range between 0.1c and 0.6c. We constrain the angle between the outflow direction of the X-ray absorber and our line of sight to be 36 o. We also detect likely variability of the absorption lines
2009
We use XSCORT, together with the hydrodynamic accretion disc wind simulation from , to calculate the impact that the accretion disk wind has on the X-ray spectrum from a 10 8 solar mass black hole Active Galactic Nuclei (AGN) accreting at 0.5 L/L Edd . The numerical simulation provides a set of self-consistent physical properties for the outflow that mitigates many of the problems inherent to previous XSCORT simulations. The properties of the resulting spectra depend on viewing angle and clearly reflect the distinct regions apparent in the original hydrodynamic simulation. Very equatorial lines-of-sight (l.o.s) encounter extremely Compton thick column densities and produce spectra that are dominated by Compton scattering and nearly-neutral absorption. Polar l.o.s encounter small, highly ionized, column densities, and result in largely featureless spectra. Finally, l.o.s that intersect the transition region between these extremes encounter moderately ionized, marginally Compton thick column densities, that imprint a wide range of absorption features on the spectrum. Both polar and transition region l.o.s produce spectra that show highly-ionized, blueshifted, Fe absorption features that are qualitatively similar to features observed in the X-ray spectra of a growing number of AGN. The spectra cannot reproduce the >8 keV lines, or the deep ∼7-13 keV absorption trough, observed in some high redshift quasars, although a considerably faster wind may well be able to
Unification of X-ray winds in Seyfert galaxies: from ultra-fast outflows to warm absorbers
Monthly Notices of the Royal Astronomical Society, 2013
The existence of ionized X-ray absorbing layers of gas along the line of sight to the nuclei of Seyfert galaxies is a well established observational fact. This material is systematically outflowing and shows a large range in parameters. However, its actual nature and dynamics are still not clear. In order to gain insights into these important issues we performed a literature search for papers reporting the parameters of the soft X-ray warm absorbers (WAs) in 35 type 1 Seyferts and compared their properties to those of the ultra-fast outflows (UFOs) detected in the same sample. The fraction of sources with WAs is >60 per cent, consistent with previous studies. The fraction of sources with UFOs is >34 per cent, >67 per cent of which also show WAs. The large dynamic range obtained when considering all the absorbers together, spanning several orders of magnitude in ionization, column, velocity and distance allows us, for the first time, to investigate general relations among them. In particular, we find significant correlations indicating that the closer the absorber is to the central black hole, the higher the ionization, column, outflow velocity and consequently the mechanical power. In all the cases, the absorbers continuously populate the whole parameter space, with the WAs and the UFOs lying always at the two ends of the distribution. These evidence strongly suggest that these absorbers, often considered of different types, could actually represent parts of a single large-scale stratified outflow observed at different locations from the black hole. The UFOs are likely launched from the inner accretion disc and the WAs at larger distances, such as the outer disc and/or torus. We argue that the observed parameters and correlations are, to date, consistent with both radiation pressure through Compton scattering and magnetohydrodynamic processes contributing to the outflow acceleration, the latter playing a major role. Most of the absorbers, especially the UFOs, show a sufficiently high mechanical power (at least ˜0.5 per cent of the bolometric luminosity) to provide a significant contribution to active galactic nuclei (AGN) feedback and thus to the evolution of the host galaxy. In this regard, we find possible evidence for the interaction of the AGN wind with the surrounding environment on large scales.
Astrophys J Suppl Ser, 2006
We present a detailed analysis of the intrinsic X-ray absorption in the Seyfert 1 galaxy NGC 4151 using Chandra/HETGS data obtained 2002 May, as part of a program which included simultaneous UV spectra using HST/STIS and FUSE. NGC 4151 was in a relatively low flux state during the observations reported here, although roughly 2.5 times as bright in the 2 --10 keV band as during a Chandra observation in 2000. The soft X-ray band was dominated by emission lines, which show no discernible variation in flux between the two observations. The 2002 data show the presence of a very highly ionized absorber, in the form of H-like and He-like Mg, Si, and S lines, as well as lower ionization gas via the presence of inner-shell absorption lines from lower-ionization species of these elements. The former is too highly ionized to be radiatively accelerated in a sub-Eddington source such as NGC 4151. We find that the lower ionization gas had a column density a factor of ~ 3 higher during the 2000 observation. If due to bulk motion, we estimate that this component must have a velocity of more than 1250 km/sec transverse to our line-of-sight. We suggest that these results are consistent with a magneto-hydrodynamic flow.
Understanding the origin of active galactic nucleus (AGN) absorption line profiles and their diversity could help to explain the physical structure of the accretion flow, and also to assess the impact of accretion on the evolution of the AGN host galaxies. Here, we present our first attempt to systematically address the issue of the origin of the complexities observed in absorption profiles. Using a simple method, we compute absorption line profiles against a continuum point source for several simulations of accretion disk winds. We investigate the geometrical, ionization, and dynamical effects on the absorption line shapes. We find that significant complexity and diversity of the absorption line profile shapes can be produced by the non-monotonic distribution of the wind velocity, density, and ionization state. Non-monotonic distributions of such quantities are present even in steady-state, smooth disk winds, and naturally lead to the formation of multiple and detached absorption troughs. These results demonstrate that the part of a wind where an absorption line is formed is not representative of the entire wind. Thus, the information contained in the absorption line is incomplete if not even insufficient to well estimate gross properties of the wind such as the total mass and energy fluxes. In addition, the highly dynamical nature of certain portions of disk winds can have important effects on the estimates of the wind properties. For example, the mass outflow rates can be off by up to two orders of magnitude with respect to estimates based on a spherically symmetric, homogeneous, constant velocity wind.
The Astrophysical Journal, 2007
Using a 100 ks XMM-Newton exposure of the well studied, low black hole mass (M BH = 1.9 × 10 6 M ⊙ ) Narrow Line Seyfert 1 NGC 4051, we show that the time evolution of the ionization state of the X-ray absorbers in response to the rapid and highly variable X-ray continuum constrains all the main physical and geometrical properties of an AGN Warm Absorber wind. We use a technique that takes advantage of the complementary high resolution in the RGS grating data and the high S/N in the EPIC CCD data. The absorber consists of two different ionization components, with a difference of ≈ 100 in ionization parameter, and a difference of ≈ 5 in column density. By tracking the response in the opacity of the gas in each component to changes in the ionizing continuum, we were able to constrain the electron density of the system. We find n e = (5.8 − 21.0) × 10 6 cm −3 for the high ionization absorber and n e >8.1×10 7 cm −3 for the low ionization absorber. Combined with the X-ray luminosity and ionization parameter, these densities require that the high and low ionization absorbing components of NGC 4051 must be compact, at distances 0.5-1.0 l-d (2200 -4400R s ) and < 3.5 l-d (< 15800R s ) from the continuum source, respectively. This rules out an origin in the dusty obscuring torus, as the dust sublimation radius is at least an order of magnitude larger (∼12 l-d), and also rules out an association with the low ionization Hβ emitting broad emission line region (radius 5.6 l-d). An accretion disk origin for the warm absorber wind is strongly suggested, and an association with the high ionization, HeII emitting, broad emission line region (radius <2 l-d) is possible. The warm absorber has a relative thickness, ∆R/R ∼ 10% -20%, and the two detected phases are consistent with pressure equilibrium, which suggests that the absorber consists of a two phase medium. A radial flow in a spherical geometry is unlikely, and a conical wind geometry is preferred. The implied mass outflow rate from this wind, can be well constrained, and is 2 − 5 % of the mass accretion rate. If the mass outflow rate scaling with accretion rate is representative of all quasars, our results imply that warm absorbers in powerful quasars are unlikely to produce important evolutionary effects on their larger environment, unless we are observing the winds before they get fully accelerated. Only in such a scenario can AGN winds be important for cosmic feedback. 1 We note that while extended and blueshifted narrow emission lines have been observed in Seyfert 2 Galaxies, it is not clear yet where these outflows (that extend for tens of parsecs away from the nucleus) originate. It is not clear either that these outflows are the same systems that form the ionized absorbers in Seyfert 1s. In §7 we will argue that the narrow emission lines and the absorption could arise from the same wind, but at very different locations.
A TWO-PHASE LOW-VELOCITY OUTFLOW IN THE SEYFERT 1 GALAXY Ark 564
The Astrophysical Journal, 2013
The Seyfert 1 galaxy Ark 564 was observed with Chandra high energy transmission gratings for 250 ks. We present the high resolution X-ray spectrum that shows several associated absorption lines. The photoionization model requires two warm absorbers with two different ionization states (logU = 0.39 ± 0.03 and logU = −0.99 ± 0.13), both with moderate outflow velocities (∼100 km s −1) and relatively low line of sight column densities (logN H = 20.94 and 20.11 cm −2). The high ionization phase produces absorption lines of O vii, O viii, Ne ix, Ne x, Mg xi, Fe xvii and Fe xviii while the low ionization phase produces lines at lower energies (O vi & O vii). The pressure-temperature equilibrium curve for the Ark 564 absorber does not have the typical "S" shape, even if the metallicity is super-solar; as a result the two warm-absorber phases do not appear to be in pressure balance. This suggests that the continuum incident on the absorbing gas is perhaps different from the observed continuum. We also estimated the mass outflow rate and the associated kinetic energy and find it to be at most 0.009% of the bolometric luminosity of Ark 564. Thus it is highly unlikely that these outflows provide significant feedback required by the galaxy formation models.
The Two-Phase, Two-Velocity Ionized Absorber in the Seyfert 1 Galaxy NGC 5548
The Astrophysical Journal, 2010
We present an analysis of X-ray high quality grating spectra of the Seyfert 1 galaxy NGC 5548 using archival Chandra-HETGS and LETGS observations for a total exposure time of 800 ks. The continuum emission (between 0.2-8 keV) is well represented by a power law (Γ = 1.6) plus a black-body component (kT = 0.1 keV). We find that the well known X-ray warm absorber in this source consists of two different outflow velocity systems. One absorbing system has a velocity of -1110 ± 150 km s −1 and the other of -490 ± 150 km s −1 . Recognizing the presence of these kinematically distinct components allows each system to be fitted independently, each with two absorption components with different ionization levels. The high velocity system consists of a component with temperature of 2.7 ± 0.6 × 10 6 K, log U = 1.23 and another component with temperature of 5.8 ± 1.0 × 10 5 K, log U = 0.67. The high-velocity, high-ionization component produces absorption by charge states Fe xxi-xxiv, while the high-velocity, lowionization component produces absorption by Ne ix-x, Fe xvii-xx, O vii-viii. The low-velocity system required also two absorbing components, one with temperature of 5.8 ± 0.8 × 10 5 K, log U = 0.67, producing absorption by Ne ix-x, Fe xvii-xx, O vii-viii. The other with lower temperature (3.5 ± 0.35 × 10 4 K), and lower ionization (log U = −0.49); producing absorption by O vi-vii and the Fe vii-xii M-shell UTA. Once these components are considered, the data do not require any further absorbers. In particular, a model consisting of a continuous radial range of ionization structures (as suggested by a previous analysis) is not required.
X-ray outflows of active galactic nuclei warm absorbers: A 900 ks Chandra simulated spectrum
We report on the performance of the statistical, X-ray absorption lines identification procedure xline-id. As illustration, it is used to estimate the time averaged gas density n H (r) of a representative AGN's warm absorber (T ≈ 10 5 K) X-ray simulated spectrum. The method relies on three key ingredients: (1) a well established emission continuum level; (2) a robust grid of photoionization models spanning several orders of magnitude in gas density (n H), plasma column density (N H), and in ionization states; (3) theoretical curves of growth for a large set of atomic lines. By comparing theoretical and observed equivalent widths of a large set of lines, spanning highly ionized charge states from O, Ne, Mg, Si, S, Ar, and the Fe L-shell and K-shell, we are able to infer the location of the X-ray warm absorber.