We present a detailed analysis of a recent, 2013 Suzaku campaign on the nearby (z = 0.184) luminous (L
bol ∼ 1047 erg s−1) quasar PDS 456. This consisted of three observations, covering a total ...duration of ∼1 Ms and a net exposure of 455 ks. During these observations, the X-ray flux was unusually low, suppressed by a factor of >10 in the soft X-ray band when compared to previous observations. We investigated the broad-band continuum by constructing a spectral energy distribution (SED), making use of the optical/UV photometry and hard X-ray spectra from the later simultaneous XMM–Newton and NuSTAR campaign in 2014. The high-energy part of this low-flux SED cannot be accounted for by physically self-consistent accretion disc and corona models without attenuation by absorbing gas, which partially covers a substantial fraction of the line of sight towards the X-ray continuum. At least two layers of absorbing gas are required, of column density log (N
H,low/cm−2) = 22.3 ± 0.1 and log (N
H,high/cm−2) = 23.2 ± 0.1, with average line-of-sight covering factors of ∼80 per cent (with typical ∼5 per cent variations) and 60 per cent (±10–15 per cent), respectively. During these observations PDS 456 displays significant short-term X-ray spectral variability, on time-scales of ∼100 ks, which can be accounted for by variable covering of the absorbing gas along the line of sight. The partial covering absorber prefers an outflow velocity of
$v_{\rm pc} = 0.25^{+0.01}_{-0.05}\,c$
at the >99.9 per cent confidence level over the case where v
pc = 0. This is consistent with the velocity of the highly ionized outflow responsible for the blueshifted iron K absorption profile. We therefore suggest that the partial covering clouds could be the denser, or clumpy part of an inhomogeneous accretion disc wind. Finally estimates are placed upon the size-scale of the X-ray emission region from the source variability. The radial extent of the X-ray emitter is found to be of the order ∼15–20R
g, although the hard X-ray (>2 keV) emission may originate from a more compact or patchy corona of hot electrons, which is typically ∼6–8R
g in size.
The evolution of galaxies is connected to the growth of supermassive black holes in their centers. During the quasar phase, a huge luminosity is released as matter falls onto the black hole, and ...radiation-driven winds can transfer most of this energy back to the host galaxy. Over five different epochs, we detected the signatures of a nearly spherical stream of highly ionized gas in the broadband x-ray spectra of the luminous quasar PDS 456. This persistent wind is expelled at relativistic speeds from the inner accretion disk, and its wide aperture suggests an effective coupling with the ambient gas. The outflow's kinetic power larger than 1046 ergs per second is enough to provide the feedback required by models of black hole and host galaxy coevolution.
Past X-ray observations of the nearby luminous quasar PDS 456 (at z = 0.184) have revealed a wide angle accretion disk wind, with an outflow velocity of ∼−0.25c. Here, we unveil a new, relativistic ...component of the wind through hard X-ray observations with NuSTAR and XMM-Newton, obtained in 2017 March when the quasar was in a low-flux state. This very fast wind component, with an outflow velocity of −0.46 0.02c, is detected in the iron K band, in addition to the −0.25c wind zone. The relativistic component may arise from the innermost disk wind, launched from close to the black hole at a radius of ∼10 gravitational radii. The opacity of the fast wind also increases during a possible obscuration event lasting for 50 ks. We suggest that the very fast wind may only be apparent during the lowest X-ray flux states of PDS 456, becoming overly ionized as the luminosity increases. Overall, the total wind power may even approach the Eddington value.
AGN X-ray spectroscopy with neural networks Parker, M L; Lieu, M; Matzeu, G A
Monthly Notices of the Royal Astronomical Society,
06/2022, Volume:
514, Issue:
3
Journal Article
Peer reviewed
Open access
ABSTRACT
We explore the possibility of using machine learning to estimate physical parameters directly from active galactic nucleus (AGN) X-ray spectra without needing computationally expensive ...spectral fitting. Specifically, we consider survey quality data, rather than long pointed observations, to ensure that this approach works in the regime where it is most likely to be applied. We simulate Athena Wide Field Imager spectra of AGN with warm absorbers, and train simple neural networks to estimate the ionization and column density of the absorbers. We find that this approach can give comparable accuracy to spectral fitting, without the risk of outliers caused by the fit sticking in a false minimum, and with an improvement of around three orders of magnitude in speed. We also demonstrate that using principal component analysis to reduce the dimensionality of the data prior to inputting it into the neural net can significantly increase the accuracy of the parameter estimation for negligible computational cost, while also allowing a simpler network architecture to be used.
ABSTRACT
We present XMM–Newton, NuSTAR, Swift, and Hubble Space Telescope observations of the Narrow-line Seyfert 1 galaxy Mrk 335 in a protracted low state in 2018 and 2019. The X-ray flux is at the ...lowest level so far observed, and the extremely low continuum flux reveals a host of soft X-ray emission lines from photoionized gas. The simultaneous UV flux drop suggests that the variability is intrinsic to the source, and we confirm this with broad-band X-ray spectroscopy. The dominance of the soft X-ray lines at low energies and distant reflection at high energies, is therefore due to the respective emission regions being located far enough from the X-ray source that they have not yet seen the flux drop. Between the two XMM–Newton spectra, taken 6 months apart, the emission line ratio in the O vii triplet changes drastically. We attribute this change to a drop in the ionization of intervening warm absorption, which means that the absorber must cover a large fraction of the line emitting region, and extend much further from the black hole than previously assumed. The HST spectrum, taken in 2018, shows that new absorption features have appeared on the blue wings of C iii*, Ly α, N v, Si iv, and C iv, likely due to absorbing gas cooling in response to the low flux state.
ABSTRACT
New Swift monitoring observations of the variable, radio-quiet quasar, PDS 456, are presented. A bright X-ray flare was captured in 2018 September, the flux increasing by a factor of 4 and ...with a doubling time-scale of 2 d. From the light crossing argument, the coronal size is inferred to be ≲30 gravitational radii for a black hole mass of 109 M⊙ and the total flare energy exceeds 1051 erg. A hardening of the X-ray emission accompanied the flare, with the photon index decreasing from Γ = 2.2 to Γ = 1.7 and back again. The flare is produced in the X-ray corona, the lack of any optical or UV variability being consistent with a constant accretion rate. Simultaneous XMM–Newton and NuSTAR observations were performed, 1–3 d after the flare peak and during the decline phase. These caught PDS 456 in a bright, bare state, where no disc wind absorption features are apparent. The hard X-ray spectrum shows a high energy roll-over, with an e-folding energy of $E_{\rm fold}=51^{+11}_{-8}$ keV. The deduced coronal temperature, of kT = 13 keV, is one of the coolest measured in any AGN and PDS 456 lies well below the predicted pair annihilation line in X-ray corona. The spectral variability, becoming softer when fainter following the flare, is consistent with models of cooling X-ray coronae. Alternatively, an increase in a non-thermal component could contribute towards the hard X-ray flare spectrum.
Abstract
We present a spectral-variability analysis of the low-redshift quasar PDS 456 using principal component analysis. In the XMM–Newton data, we find a strong peak in the first principal ...component at the energy of the Fe absorption line from the highly blueshifted outflow. This indicates that the absorption feature is more variable than the continuum, and that it is responding to the continuum. We find qualitatively different behaviour in the Suzaku data, which is dominated by changes in the column density of neutral absorption. In this case, we find no evidence of the absorption produced by the highly ionized gas being correlated with this variability. Additionally, we perform simulations of the source variability, and demonstrate that PCA can trivially distinguish between outflow variability correlated, anticorrelated and un-correlated with the continuum flux. Here, the observed anticorrelation between the absorption line equivalent width and the continuum flux may be due to the ionization of the wind responding to the continuum. Finally, we compare our results with those found in the narrow-line Seyfert 1 IRAS 13224–3809. We find that the Fe K UFO feature is sharper and more prominent in PDS 456, but that it lacks the lower energy features from lighter elements found in IRAS 13224–3809, presumably due to differences in ionization.
Abstract
We report the first Atacama large millimeter/submillimeter array observations of MCG-03-58-007, a local (z = 0.03236 ± 0.00002, this work) AGN ($L_{\mathrm{ AGN}\mathrm{ }}\sim 10^{45}~\rm ...erg~s^{-1}$), hosting a powerful X-ray ultrafast (v = 0.1c) outflow (UFO). The CO(1-0) line emission is observed across ∼18 kpc scales with a resolution of $\sim 1\, \rm kpc$. About 78 per cent of the CO(1-0) luminosity traces a galaxy-size rotating disc. However, after subtracting the emission due to such rotating disc, we detect with a S/N = 20 a residual emission in the central ∼4 kpc. Such residuals may trace a low velocity (vLOS = 170 km s−1) outflow. We compare the momentum rate ($\dot{P}$) and kinetic power ($\dot{E}$) of such putative molecular outflow with that of the X-ray UFO and find $\dot{P}_{\mathrm{ mol}}/\dot{P}_{\mathrm{ UFO}}\sim 0.4$ and $\dot{E}_{\mathrm{ mol}}/\dot{E}_{\mathrm{ UFO}}\sim 4\times 10^{-3}$. This result is at odds with the energy-conserving scenario suggested by the large momentum boosts measured in some other molecular outflows. An alternative interpretation of the residual CO emission would be a compact rotating structure, distinct from the main disc, which would be a factor of ∼10–100 more extended and massive than typical circumnuclear discs revealed in Seyferts. In conclusion, in both scenarios, our results rule out the hypothesis of a momentum-boosted molecular outflow in this AGN, despite the presence of a powerful X-ray UFO.
Abstract
We present a newly discovered correlation between the wind outflow velocity and the X-ray luminosity in the luminous (Lbol ∼ 1047erg s − 1) nearby (z = 0.184) quasar PDS 456. All the ...contemporary XMM–Newton, NuSTAR and Suzaku observations from 2001–2014 were revisited and we find that the centroid energy of the blueshifted Fe K absorption profile increases with luminosity. This translates into a correlation between the wind outflow velocity and the hard X-ray luminosity (between 7 and 30 keV) where we find that $v_{\rm w}/c\propto L_{7-30}^{\gamma }$ where γ = 0.22 ± 0.04. We also show that this is consistent with a wind that is predominately radiatively driven, possibly resulting from the high Eddington ratio of PDS 456.
ABSTRACT
We present joint XMM–Newton and NuSTAR observations of the ‘bare’ narrow-line Seyfert 1 Ton S180 (z = 0.062), carried out in 2016 and providing the first hard X-ray view of this luminous ...galaxy. We find that the 0.4–30 keV band cannot be self-consistently reproduced by relativistic reflection models, which fail to account simultaneously for the soft and hard X-ray emission. The smooth soft excess prefers extreme blurring parameters, confirmed by the nearly featureless nature of the Reflection Grating Spectrometer (RGS) spectrum, while the moderately broad Fe K line and the modest hard excess above 10 keV appear to arise in a milder gravity regime. By allowing a different origin of the soft excess, the broad-band X-ray spectrum and overall spectral energy distribution (SED) are well explained by a combination of (a) direct thermal emission from the accretion disc, dominating from the optical to the far/extreme UV; (b) Comptonization of seed disc photons by a warm (kTe ∼ 0.3 keV) and optically thick (τ ∼ 10) corona, mostly contributing to the soft X-rays; (c) Comptonization by a standard hot ($kT_{\rm \mathrm{ e}}\gtrsim 100$ keV) and optically thin (τ < 0.5) corona, responsible for the primary X-ray continuum; and (d) reflection from the mid/outer part of the disc. The two coronae are suggested to be rather compact, with $R_{\rm hot}\lesssim R_{\rm warm}\lesssim 10\, r_{\rm g}$. Our SED analysis implies that Ton S180 accretes at super-Eddington rates. This is a key condition for the launch of a wind, marginal (i.e. 3.1σ significance) evidence of which is indeed found in the RGS spectrum.
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