Abstract
The unusual behavior of the spectral lines of NGC5548 during the STORM campaign demonstrated a missing piece in the structure of AGNs. For a two-month period in the middle of the campaign, ...the spectral lines showed a deficit in flux and a reduced response to the variations of the UV continuum. This was the first time that this behavior was unequivocally observed in an AGN. Our previous papers explained this as being due to a variable disk wind that acts as a shield and alters the SED. Here, we use Cloudy to create an atlas of photoionization models for a variety of disk winds, in order to study their effects on the SED. We show that the winds have three different cases: Case 1 winds are transparent, fully ionized, and have minimal effects on the intrinsic SED, although they can produce some line emission, especially He
ii
or FeK
α
. We propose that this is the situation in most of the AGNs. Case 2 winds, which have a He
++
–He
+
ionization front, block part of the XUV continuum but transmit much of the Lyman continuum. They lead to the observed abnormal behavior. Case 3 winds have a H
+
ionization front and block much of the Lyman continuum. The results show that the presence of these winds has important effects on the spectral lines of AGNs. They will thus have an effect on the measurements of the black hole mass and the geometry of the AGN. This atlas of spectral simulations can serve as a guide to future reverberation campaigns.
The X-ray/UV absorber in NGC 4593 Ebrero, J; Kaastra, J. S; Kriss, G. A ...
Monthly notices of the Royal Astronomical Society,
11/2013, Letnik:
435, Številka:
4
Journal Article
Recenzirano
We present the results of a recent (2011 March) 160 ks Chandra-LETGS (Low Energy Transmission Grating Spectrometre) observation of the Seyfert galaxy NGC 4593, and the analysis of archival X-ray and ...UV spectra taken with XMM-Newton and Hubble Space Telescope (HST)/STIS (Space Telescope Imaging Spectrograph) in 2002. We find evidence of a multi-component warm absorber (WA) in the X-rays with four distinct ionization degrees (log ξ = 1.0, log ξ = 1.7, log ξ = 2.4 and log ξ = 3.0) outflowing at several hundreds of km s−1. In the UV we detect 15 kinematic components in the absorbers, blueshifted with respect to the systemic velocity of the source, ranging from −60 km s−1 to −1520 km s−1. Although the predicted C iv and N v column densities from the low-ionization X-ray outflow are in agreement with those measured for some components in the STIS spectrum, there are kinematic discrepancies that may prevent both the X-ray and UV absorbers from originating in the same intervening gas. We derive upper limits on the location of the absorbers finding that the high-ionization gas lies within ∼6-29 pc from the central ionizing source, while the low-ionization gas is located at several hundreds of pc. This is consistent with our line of sight passing through different parts of a stratified wind. The total kinetic energy of the outflows injected into the surroundings of the host galaxy only accounts for a tiny fraction of the bolometric luminosity of the source and it is therefore unlikely that they may cause a significant impact on the interstellar medium of NGC 4593 in a given single episode of activity.
In 2013, we conducted a large multi-wavelength campaign on the archetypical Seyfert 1 galaxy NGC 5548. Unexpectedly, this usually unobscured source appeared strongly absorbed in the soft X-rays ...during the entire campaign, and signatures of new and strong outflows were present in the almost simultaneous UV HST/COS data. Here we carry out a comprehensive spectral analysis of all available XMM-Newton observations of NGC 5548 (precisely 14 observations from our campaign plus three from the archive, for a total of ~763 ks) in combination with three simultaneous NuSTAR observations. We obtain a best-fit underlying continuum model composed by i) a weakly varying flat (Gamma ~ 1.5-1.7) power-law component; ii) a constant, cold reflection (FeK + continuum) component; iii) a soft excess, possibly owing to thermal Comptonization; and iv) a constant, ionized scattered emission-line dominated component. Our main findings are that, during the 2013 campaign, the first three of these components appear to be partially covered by a heavy and variable obscurer that is located along the line of sight (LOS), which is consistent with a multilayer of cold and mildly ionized gas. We characterize in detail the short timescale (mostly ~ks-to-days) spectral variability of this new obscurer, and find it is mostly due to a combination of column density and covering factor variations, on top of intrinsic power-law (flux and slope) variations. In addition, our best-fit spectrum is left with several (but marginal) absorption features at rest-frame energies ~6.7-6.9 keV and ~8 keV, aswell as a weak broad emission line feature redwards of the 6.4 keV emission line. These could indicate a more complex underlying model, e.g. a P-Cygni-type emission profile if we allow for a large velocity and wide-angle outflow. These findings are consistent with a picture where the obscurer represents the manifestation along the LOS of a multilayer of gas, which is also in multiphase, and which is likely outflowing at high speed, and simultaneously producing heavy obscuration and scattering in the X-rays, as well as broad absorption features in the UV.
Aims: More than half of all active galactic nuclei show strong photoionised outflows. A major uncertainty in models for these outflows is the distance of the gas to the central black hole. We use the ...results of a massive multiwavelength monitoring campaign on the bright Seyfert 1 galaxy Mrk 509 to constrain the location of the outflow components dominating the soft X-ray band. Methods: Mrk 509 was monitored by XMM-Newton and other satellites in 2009. We have studied the response of the photoionised gas to the changes in the ionising flux produced by the central regions. We used the five discrete ionisation components A-E that we detected in the time-averaged spectrum taken with the RGS instrument. By using the ratio of fluxed EPIC-pn and RGS spectra, we were able to put tight constraints on the variability of the absorbers. Monitoring with the Swift satellite started six weeks before the XMM-Newton observations. This allowed us to use the history of the ionising flux and to develop a model for the time-dependent photoionisation in this source. Results: Components A and B are too weak for variability studies, but the distance for component A is already known from optical imaging of the O iii line to be about 3 kpc. During the five weeks of the XMM-Newton observations we found no evidence of changes in the three X-ray dominant ionisation components C, D, and E, despite a huge soft X-ray intensity increase of 60% in the middle of our campaign. This excludes high-density gas close to the black hole. Instead, using our time-dependent modelling, we find that the density is very low, and we derive firm lower limits to the distance of these components. For component D we find evidence for variability on longer time scales by comparing our spectra to archival data taken in 2000 and 2001, yielding an upper limit to the distance. For component E we derive an upper limit to the distance based on the argument that the thickness of the absorbing layer must be less than its distance to the black hole. Combining these results, at the 90% confidence level, component C has a distance of >70 pc, component D is between 5-33 pc, and component E has a distance >5 pc but smaller than 21-400 pc, depending upon modelling details. These results are consistent with the upper limits that we derived from the HST/COS observations of our campaign and point to an origin of the dominant, slow (v < 1000 km s-1) outflow components in the NLR or torus-region of Mrk 509.
We present the results of our 600 ks RGS observation as part of the multiwavelength campaign on Mrk 509. The very high quality of the spectrum allows us to investigate the ionized outflow with an ...unprecedented accuracy due to the long exposure and the use of the RGS multipointing mode. We detect multiple absorption lines from the interstellar medium and from the ionized absorber in Mrk 509. A number of emission components are also detected, including broad emission lines consistent with an origin in the broad line region, the narrow O vii forbidden emission line and also (narrow) radiative recombination continua. The ionized absorber consists of two velocity components (v = -13 ± 11 km s-1 and v = -319 ± 14 km s-1), which both are consistent with earlier results, including UV data. There is another tentative component outflowing at high velocity, -770 ± 109 km s-1, which is only seen in a few highly ionized absorption lines. The outflow shows discrete ionization components, spanning four orders of magnitude in ionization parameter. Due to the excellent statistics of our spectrum, we demonstrate for the first time that the outflow in Mrk 509 in the important range of log ξ between 1-3 cannot be described by a smooth, continuous absorption measure distribution, but instead shows two strong, discrete peaks. At the highest and lowest ionization parameters we cannot differentiate smooth and discrete components.
Anatomy of the AGN in NGC 5548 Di Gesu, L; Costantini, E; Ebrero, J ...
Astronomy and astrophysics (Berlin),
7/2015, Letnik:
579
Journal Article
Recenzirano
During an extensive multiwavelength campaign that we performed in 2013-2014, we found the prototypical Seyfert 1 galaxy NGC 5548 in an unusual condition of heavy and persistent obscuration. The newly ...discovered "obscurer" absorbs most of the soft X-ray continuum along our line of sight and lowers the ionizing luminosity received by the classical warm absorber. We present the analysis of the high resolution X-ray spectra collected with XMM-Newton and Chandra throughout the campaign, which are suitable to investigate the variability of both the obscurer and classical warm absorber. The time separation between these X-ray observations range from two days to eight months. On these timescales the obscurer is variable both in column density and in covering fraction. This is consistent with the picture of a patchy wind. The most significant variation occurred in September 2013 when the source brightened for two weeks. A higher and steeper intrinsic continuum and a lower obscurer covering fraction are both required to explain the spectral shape during the flare. We suggest that a geometrical change of the soft X-ray source behind the obscurer causes the observed drop in the covering fraction. Because of the higher soft X-ray continuum level, the September 2013 Chandra spectrum is the only X ray spectrum of the campaign in which individual features of the warm absorber could be detected. The spectrum shows absorption from Fe-UTA, O IV, and O V, consistent with belonging to the lower-ionization counterpart of the historical NGC 5548 warm absorber. Hence, we confirm that the warm absorber has responded to the drop in the ionizing luminosity caused by the obscurer.
We obtained high-resolution Far Ultraviolet Spectroscopic Explorer (FUSE; R approx 20,000) and Very Large Telescope (VLT; R approx 45,000) spectra of the quasar HE 2347-4342 in order to study the ...properties of the intergalactic medium between redshifts z = 2.0 and 2.9. The high-quality optical spectrum allows us to identify approximately 850 H I absorption lines with column densities between N approx 5 x 10 super(11) and 10 super(18) cm super(-2). The reprocessed FUSE spectrum extends the wavelength coverage of the H IIE absorption down to an observed wavelength of 920 Aa. Source flux is detected to rest-frame wavelengths as short as approx237 Aa. Approximately 1400 H IIE absorption lines are identified, including 917 H IIE Lyalpha systems and some of their H IIE Ly beta , Lygamma, and Ly delta counterparts. The ionization structure of H IIE is complex, with approximately 90 absorption lines that are not detected in the hydrogen spectrum. These features may represent the effect of soft ionizing sources. The ratio eta = N(He imageimage)/N(H image) varies approximately from unity to more than a thousand, with a median value of 62 and a distribution consistent with the intrinsic spectral indexes of quasars. This provides evidence that the dominant ionizing field is from the accumulated quasar radiation, with contributions from other soft sources such as star- forming regions and obscured active galactic nuclei, which do not ionize helium. We find an evolution in eta toward smaller values at lower redshift, with the gradual disappearance of soft components. At redshifts z > 2.7, the large but finite increase in the H IIE opacity, tau = 5 plus or minus 1, suggests that we are viewing the end stages of a reionization process that began at an earlier epoch. Fits of the absorption profiles of unblended lines indicate comparable velocities between hydrogen and He super(+) ions. For line widths bimage = xib sub(H), we find xi = 0.95 plus or minus 0.12, indicating a velocity field in the intergalactic medium dominated by turbulence. At hydrogen column densities N < 3 x 10 super(12) cm super(-2), the number of forest lines shows a significant deficit relative to a power law and becomes negligible below N = 10 super(11) cm super(-2).
Multiwavelength campaign on Mrk 509 Costantini, E; Kriss, G; Kaastra, J S ...
Astronomy and astrophysics (Berlin),
11/2016, Letnik:
595
Journal Article
Recenzirano
Aims. We model the broad emission lines present in the optical, UV, and X-ray spectra of Mrk 509, a bright type 1 Seyfert galaxy. The broad lines were simultaneously observed during a large ...multiwavelength campaign, using the XMM-Newton-OM for the optical lines, HST-COS for the UV lines, and XMM-Newton-RGS and Epic for the X-ray lines. We also used FUSE archival data for the broad lines observed in the far-ultraviolet. The goal is to find a physical connection among the lines measured at different wavelengths and to determine the size and the distance from the central source of the emitting gas components. Methods. We used the Locally Optimally emission Cloud (LOC) model which interprets the emissivity of the broad line region (BLR) as regulated by power law distributions of both gas density and distances from the central source. Results. We find that one LOC component cannot model all the lines simultaneously. In particular, we find that the X-ray and UV lines may likely originate in the more internal part of the AGN at radii in the range ~5 x 10 super(14)-3 x 10 super(17)cm, while the optical lines and part of the UV lines may likely originate farther out at radii ~3 x 10 super(17)-3 x 10 super(18)cm. These two gas components are parametrized by a radial distribution of the luminosities with a slope gamma of ~1.15 and ~1.10, respectively, both of them covering at least 60% of the source. This simple parametrization points to a structured broad line region where the higher ionized emission comes from closer in, while the emission of the low-ionization lines is more concentrated in the outskirts of the broad line region.
We conducted a multi-wavelength 6-month campaign to observe the Seyfert Galaxy NGC 7469, using the space-based observatories HST, Swift, XMM-Newton and NuSTAR. We report the results of the spectral ...analysis of the seven simultaneous XMM-Newton and NuSTAR observations. The source shows significant flux variability within each observation, but the average flux is less variable among the different pointings of our campaign. Our spectral analysis reveals a prominent narrow neutral Fe Kα emission line in all the spectra and weaker contributions from Fe Kβ, neutral Ni Kα, and ionized iron. We find no evidence for variability or relativistic effects acting on the emission lines, which indicates that they originate from distant material. In the joint analysis of XMM-Newton and NuSTAR data, a constant photon index is found (Γ = 1.78 ± 0.02) together with a high energy cut-off Ecut = 170−40+60 $E_{\rm{cut}}=170^{+60}_{-40}$Ecut=170−40+60 keV. Adopting a self-consistent Comptonization model, these values correspond to an average coronal electron temperature of kT = 45−12+15 $kT=45^{+15}_{-12}$kT=45−12+15 keV and, assuming a spherical geometry, an optical depth τ = 2.6 ± 0.9. The reflection component is consistent with being constant and the reflection fraction is in the range R = 0.3−0.6. A prominent soft excess dominates the spectra below 4 keV. This is best fit with a second Comptonization component, arising from a warm corona with an average kT = 0.67 ± 0.03 keV and a corresponding optical depth τ = 9.2 ± 0.2.
Aims: Active galactic nuclei (AGN) often show evidence of photoionized outflows. A major uncertainty in models for these outflows is the distance (R) to the gas from the central black hole. In this ...paper we use the HST/COS data from a massive multi-wavelength monitoring campaign on the bright Seyfert I galaxy Mrk 509, in combination with archival HST/STIS data, to constrain the location of the various kinematic components of the outflow. Methods: We compare the expected response of the photoionized gas to changes in ionizing flux with the changes measured in the data using the following steps: 1) We compare the column densities of each kinematic component measured in the 2001 STIS data with those measured in the 2009 COS data; 2) We use time-dependent photionization calculations with a set of simulated lightcurves to put statistical upper limits on the hydrogen number density (nH) that are consistent with the observed small changes in the ionic column densities; 3) From the upper limit on nH, we calculate a lower limit on the distance to the absorber from the central source via the prior determination of the ionization parameter. Our method offers two improvements on traditional timescale analysis. First, we account for the physical behavior of AGN lightcurves. Second, our analysis accounts for the quality of measurement in cases where no changes are observed in the absorption troughs. Results: The very small variations in trough ionic column densities (mostly consistent with no change) between the 2001 and 2009 epochs allow us to put statistical lower limits on R between 100-200 pc for all the major UV absorption components at a confidence level of 99%. These results are mainly consistent with the independent distance estimates derived for the warm absorbers from the simultaneous X-ray spectra. Based on the 100-200 pc lower limit for all the UV components, this absorber cannot be connected with an accretion disc wind. The outflow might have originated from the disc, but based on simple ballistic kinematics, such an event had to occur at least 300 000 years ago in the rest frame of the source.
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