Context. Accretion models predict that fluorescence lines broadened by relativistic effects should arise from reflection of X-ray emission onto the inner region of the accretion disc surrounding the ...central black hole of active galactic nuclei (AGN). The theory behind the origin of relativistic lines is well established, and observational evidence from a moderate number of sources seems to support the existence of these lines. Aims: The aim of this work is to establish the fraction of AGN with relativistic Fe Kα lines, and study possible correlations with source physical properties. Methods: An XMM-Newton collection of 149 radio-quiet Type 1 AGN has been systematically and uniformly analysed in order to search for evidence of a relativistically broadened Fe Kα line. To enable statistical studies, an almost complete, flux-limited subsample of 31 sources has been defined by selecting the FERO sources observed by the RXTE all-sky Slew Survey with a count rate in the 3-8 keV energy band greater than 1 cts/sec. The 2-10 keV spectra of the FERO sources where compared with a complex model including most of the physical components observed in the X-ray spectra of Seyfert galaxies: a power law primary continuum modified by non-relativistic Compton reflection and warm absorption, plus a series of narrow Fe line reflection features. Results: The observed fraction of sources in the flux-limited sample that show strong evidence of a relativistic Fe Kα line is 36%. This number can be interpreted as a lower limit to the fraction of sources that present a relativistic broad Fe Kα line in the wider AGN population. The average line equivalent width (EW) is of the order of 100 eV. The outcome of the fit yields an average disc inclination angle of 28 ± 5° and an average power-law index of the radial disc emissivity law of 2.4 ± 0.4. The spin value is well constrained only in 2 cases (MCG-6-30-15 and MRK 509); in the rest of the cases, whenever a constraint can be placed, it always implies the rejection of the static black hole solution. The Fe Kα line EW does not correlate with disc parameters or with system physical properties, such as black hole mass, accretion rate, and hard X-ray luminosity. Appendices are only available in electronic form at www.aanda.org
ABSTRACT
The narrow-line Seyfert 1 galaxy IRAS 17020+4544 is one of the few sources where both an X-ray ultrafast outflow and a molecular outflow were observed to be consistent with energy ...conservation. However, IRAS 17020+4544 is less massive and has a much more modest active galactic nucleus (AGN) luminosity than the other examples. Using recent CO(1–0) observations with the NOrthern Extended Millimeter Array, we characterized the molecular gas content of the host galaxy for the first time. We found that the molecular gas is distributed into an apparent central disc of 1.1 × 109 M⊙, and a northern extension located up to 8 kpc from the centre with a molecular gas mass $M_{\mathrm{ H}_2}\sim 10^8\, \mathrm{ M}_\odot$. The molecular gas mass and the CO dynamics in the northern extension reveal that IRAS 17020+4544 is not a standard spiral galaxy, instead it is interacting with a dwarf object corresponding to the northern extension. This interaction possibly triggers the high accretion rate on to the supermassive black hole. Within the main galaxy, which hosts the AGN, a simple analytical model predicts that the molecular gas may lie in a ring, with less molecular gas in the nuclear region. Such distribution may be the result of the AGN activity that removes or photodissociates the molecular gas in the nuclear region (AGN feedback). Finally, we have detected a molecular outflow of mass $M_{\mathrm{ H}_2}=(0.7\!-\!1.2)\times 10^7\, \mathrm{ M}_\odot$ in projection at the location of the northern galaxy, with a similar velocity to that of the massive outflow reported in previous millimetre data obtained by the Large Millimeter Telescope.
Abstract
In this work, we present the results of the survey carried out on one of the deepest X-ray fields observed by the XMM-Newton satellite. The 1.75 Ms Ultra Narrow Deep Field (XMM175UNDF) ...survey is made by 13 observations taken over 2 yr with a total exposure time of 1.75 Ms (1.372 Ms after flare-filtered) in a field of 30′ × 30′ centered around the blazar 1ES 1553+113. We stacked the 13 observations reaching flux limits of 4.03 × 10
−16
, 1.3 × 10
−15
, and 9.8 × 10
−16
erg s
−1
cm
−2
in the soft (0.2–2 keV), hard (2–12 keV), and full (0.2–12 keV) bands, respectively. Using a conservative threshold of Maximum Likelihood significance of ML ≥ 6, corresponding to 3
σ
, we detected 301 point-sources for which we derived positions, fluxes in different bands, and hardness ratios. Thanks to an optical follow-up that was carried out using the 10.4m the Gran Telescopio Canarias on the same field in the
u
′
g
′
r
′
i
′
z
′ bands, combined with WISE/2MASS IR data, we identified 244 optical/IR counterpart candidates for our X-ray sources and estimated their X-ray luminosities, redshift distribution, X-ray/optical–X-ray/IR flux ratios, and absolute magnitudes. Finally, we divided this subsample into 40 non-active sources and 204 active galactic nuclei, of which 139 are classified as Seyfert galaxies and 41 as Quasars.
Context. The unified scenario for active galactic nuclei (AGN) postulates that our orientation with respect to a parsec-scale azimuthally-symmetric gas and dust system causes the difference in their ...phenomenology in the optical/UV and X-ray bands. Only recently have high-resolution radio (VLBI) and IR interferometric observations provided direct constraints on the size and structure of this obscuring system (known historically as the “torus”). On the other hand, variability in optically-thick X-ray absorption and reprocessing in heavily obscured AGN often probe smaller scales, down to the broad line region and beyond. Aims. We aim at constraining the geometry of the reprocessing matter in the nearby prototypical Seyfert 2 Galaxy Markarian 3 by studying the time evolution of the spectral components associated to the primary AGN emission and to its Compton-scattering. Methods. We analyzed archival spectroscopic observations of Markarian 3 taken over the last ≃ 12 years with the XMM-Newton, Suzaku and Swift observatories, as well as data taken during a monitoring campaign activated by us in 2012. Results. The timescale of the Compton-reflection component variability (originally discovered by ASCA in the mid-’90s) is ≲ 64 days. This upper limit improves by more than a factor of 15 on previous estimates of the Compton-reflection variability timescale for this source. When the light curve of the Compton-reflection continuum in the 4−5 keV band is correlated with the 15–150 keV Swift/BAT curve, a delay ≳1200 days is found. The cross-correlation results depend on the model used to fit the spectra, although the detection of the Compton-reflection component variability is independent of the range of models employed to fit the data. Reanalysis of an archival Chandra image of Markarian 3 indicates that the Compton-reflection and the Fe Kα emitting regions are extended to the north up to ≃300 pc. The combination of these findings suggests that the optically-thick reprocessor in Markarian 3 is clumpy. Conclusions. There is mounting experimental evidence that the structure of the optically-thick gas and dust in the nuclear environment of nearby heavily obscured AGN is extended and complex. We discuss possible modifications to the standard unification scenarios encompassing this complexity. Markarian 3, which exhibits X-ray absorption and reprocessing on widely different spatial scales, is an ideal laboratory to test these models.
Aims. NGC2617 is a nearby (z~ 0.01) active galaxy that recently switched from being a Seyfert 1.8 to be a Seyfert 1.0. At the same time, it underwent a strong increase of X-ray flux by one order of ...magnitude with respect to archival measurements. We characterise the X-ray spectral and timing properties of NGC2617 with the aim of studying the physics of a changing-look active galactic nucleus (AGN). Methods. We performed a comprehensive timing and spectral analysis of two XMM-Newton pointed observations spaced by one month, complemented by archival quasi-simultaneous INTEGRAL observations. Results. We found that, to the first order, NGC2617 looks like a type 1 AGN in the X-ray band and, with the addition of a modest reflection component, its continuum can be modelled well either with a power law plus a phenomenological blackbody, a partially covered power law, or a double Comptonisation model. Independent of the continuum adopted, in all three cases a column density of a few 10 super(23) cm super(-2) of neutral gas covering 20-40% of the continuum source is required by the data. Most interestingly, absorption structures due to highly ionised iron have been detected in both observations with a redshift of about 0.1c with respect to the systemic redshift of the host galaxy. Conclusions. The redshifted absorber can be ascribed to a failed wind/aborted jets component, to gravitational redshift effects, and/or to matter directly falling towards the central supermassive black hole. In either case, we are probing the innermost accretion flow around the central supermassive black hole of NGC2617 and might be even watching matter in a direct inflow towards the black hole itself.
Recent high-resolution measurements suggest that the soft X-ray spectrum of obscured radio galaxies exhibits signatures of photoionized gas (e.g. 3C 445 and 3C 33) similar to those observed in ...radio-quiet obscured active galactic nuclei. While signatures of warm absorbing gas covering a wide range of temperature and ionization states have been detected in about one-half of the population of nearby type 1 Seyfert galaxies, no traces of warm absorber gas have been reported to date in the high-resolution spectra of broad-line radio galaxies (BLRG). We present here the first detection of a soft X-ray warm absorber in the powerful Fanaroff–Riley type II BLRG 3C 382 using the Reflection Grating Spectrometer on-board XMM–Newton. The absorption gas appears to be highly ionized, with column density of the order of 1022 cm−2, ionization parameter log ξ > 2 erg cm s−1 and outflow velocities of the order of 103 km s−1. The absorption lines may come from regions located outside the torus, however, at distances less than 60 pc. This result may indicate that a plasma ejected at velocities near the speed of light and a photoionized gas with slower outflow velocities can coexist in the same source beyond the broad-line regions.
In this work, the analysis of multi-epoch (1995–2010) X-ray observations of the Seyfert 1 galaxy H0557-385 is presented. The wealth of data presented in this analysis show that the source exhibits ...dramatic spectral variability, from a typical unabsorbed Seyfert 1 type spectrum to a Compton-thin absorbed state, on time-scales of ∼5 yr. This extreme change in spectral shape can be attributed to variations in the column density and covering fraction of a neutral absorbing medium attenuating the emission from the central continuum source. Evidence for Compton reflection of the intrinsic nuclear emission is present in each of the spectra, though this feature is most prominent in the low-state spectra, where the associated Fe emission line complex is clearly visible. In addition to the variable absorbing medium, a warm absorber component has been detected in each spectral state. Optical spectroscopy concurrent with the 2010 XMM–Newton observation campaign has detected the presence of broad optical emission lines during an X-ray absorption event. From the analysis of both X-ray and optical spectroscopic data, it has been inferred that the X-ray spectral variability is a result of obscuration of the central emission region by a clumpy absorber covering ≥ 80 per cent of the source with an average column density of N
H ∼ 7 × 1023 cm−2, and which is located outside the broad line region at a distance from the central source consistent with the dust sublimation radius of the AGN.
Context. The morphology of the circumnuclear gas accreting onto supermassive black holes in Seyfert galaxies remains a topic of much debate. As the innermost regions of active galactic nuclei (AGN) ...are spatially unresolved, X-ray spectroscopy, and in particular line-of-sight absorption variability, is a key diagnostic to map out the distribution of gas. Aims. Observations of variable X-ray absorption in multiple Seyferts and over a wide range of timescales indicate the presence of clumps/clouds of gas within the circumnuclear material. Eclipse events by clumps transiting the line of sight allow us to explore the properties of the clumps over a wide range of radial distances from the optical/UV broad line region (BLR) to beyond the dust sublimation radius. Time-resolved absorption events have been extremely rare so far, but suggest a range of density profiles across Seyferts. We resolve a weeks-long absorption event in the Seyfert NGC 3227. Methods. We examine six Suzaku and 12 Swift observations from a 2008 campaign spanning five weeks. We use a model accounting for the complex spectral interplay of three absorbers with different levels of ionization. We perform time-resolved spectroscopy to discern the absorption variability behavior. We also examine the IR to X-ray spectral energy distribution (SED) to test for reddening by dust. Results. The 2008 absorption event is due to moderately-ionized (log ξ ~ 1.2–1.4) gas covering 90% of the line of sight. We resolve the density profile to be highly irregular, in contrast to a previous symmetric and centrally-peaked event mapped with RXTE in the same object. The UV data do not show significant reddening, suggesting that the cloud is dust-free. Conclusions. The 2008 campaign has revealed a transit by a filamentary, moderately-ionized cloud of variable density that is likely located in the BLR, and possibly part of a disk wind.
Abstract
We report on the redshift of the BL Lac object 3FGL J0909.0+2310 based on observations obtained with the OSIRIS Multi-Object Spectrograph (MOS) mounted on the 10.4-m Gran Telescopio ...Canarias. A redshift of 0.432 ± 0.002 was obtained by the identification of three absorption features (Ca ii K&H and the G band) detected in the spectrum of the BL Lac host galaxy. The closest object to the BL Lac at an angular separation of 3.8 arcsec (∼21 kpc at this distance) has a similar redshift of 0.431 ± 0.002. This companion galaxy could be the most likely cause of the nuclear activity as postulated by studies based on more extended data sets and cosmological models. MOS allows us to study the object's neighbourhood within a field of view of approximately 7 × 2 arcmin2 and we find two small groups of galaxies at redshifts 0.28 and 0.39 which are probably not related to the activity of 3FGL J0909.0+2310.
Context. Soft X-ray high resolution spectroscopy of obscured AGNs shows a complex soft X-ray spectrum dominated by emission lines of He and H-like transitions of elements from carbon to neon, as well ...as L-shell transitions due to iron ions. Aims. In this paper we characterize the XMM-Newton RGS spectrum of the Seyfert 1 galaxy NGC 4051 observed during a low flux state and infer the physical properties of the emitting and absorbing gas in the soft X-ray regime. Methods. X-ray high-resolution spectroscopy offers a powerful diagnostic tool because the observed spectral features strongly depend on the physical properties of matter (ionization parameter U, electron density ne, hydrogen column density NH), which in turn are tightly related to the location and size of the X-ray emitting clouds. We carried out a phenomenological study to identify the atomic transitions detected in the spectra. This study suggests that the spectrum is dominated by emission from a photoionized plasma. Then we used the photoionization code Cloudy to produce synthetic models for the emission line component and the warm absorber observed during phases of high intrinsic luminosity. Results. The low state spectrum cannot be described by a single photoionization component. A multi-ionization phase gas with an ionization parameter in the range of log U ~ 0.63–1.90 and a column density log NH = 22.10–22.72 cm-2 is required, while the electron density ne remains unconstrained. A warm absorber medium is required by the fit with the parameters log U ~ 0.85, log NH = 23.40 and log ne $\la$ 5. The model is consistent with an X-ray emitting region at a distance $\ga$ 5 × 10-2 pc from the central engine.
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