Absorption from a multi‐layer circumnuclear medium and reflection from the accretion disc in NGC 1365

Risaliti, G.

doi:10.1002/asna.201612342

Cited by 5 publications

(5 citation statements)

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“…NGC 1365 is one of the unique sources showing frequent changes in its obscuration state. Recently, Risaliti (2016) summarized the various observational aspects of this source and proposed a multi-layer structure of the circumnuclear medium to explain all the observed absorption states and their variability. NGC 1365 has been observed several times in reflectiondominated states, suggesting the presence of a layer of neutral Compton-thick (N H > 10 24 cm −2 ) absorber located at a distance of the order of or larger than that of the broad line region (Risaliti et al 2007).…”

Section: Motivation and Methodsmentioning

confidence: 99%

Testing the accuracy of reflection-based supermassive black hole spin measurements in AGN

Kammoun

Nardini

Risaliti

2018

A&A

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Context. X-ray reflection is a very powerful method to assess the spin of supermassive black holes (SMBHs) in active galactic nuclei (AGN), yet this technique is not universally accepted. Indeed, complex reprocessing (absorption, scattering) of the intrinsic spectra along the line of sight can mimic the relativistic effects on which the spin measure is based. Aims. In this work, we test the reliability of SMBH spin measurements that can currently be achieved through the simulations of high-quality XMM-Newton and NuSTAR spectra. Methods. Each member of our group simulated ten spectra with multiple components that are typically seen in AGN, such as warm and (partial-covering) neutral absorbers, relativistic and distant reflection, and thermal emission. The resulting spectra were blindly analysed by the other two members.Results. Out of the 60 fits, 42 turn out to be physically accurate when compared to the input model. The SMBH spin is retrieved with success in 31 cases, some of which (9) are even found among formally inaccurate fits (although with looser constraints). We show that, at the high signal-to-noise ratio assumed in our simulations, neither the complexity of the multi-layer, partial-covering absorber nor the input value of the spin are the major drivers of our results. The height of the X-ray source (in a lamp-post geometry) instead plays a crucial role in recovering the spin. In particular, a success rate of 16 out of 16 is found among the accurate fits for a dimensionless spin parameter larger than 0.8 and a lamp-post height lower than five gravitational radii.

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Section: Motivation and Methodsmentioning

confidence: 99%

Testing the accuracy of reflection-based supermassive black hole spin measurements in AGN

Kammoun

Nardini

Risaliti

2018

A&A

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“…This "static" view, in which the torus is made of a smooth dusty distribution, has been questioned in recent years by several studies (e.g., Elitzur & Shlosman 2006;Nenkova et al 2008; quality data from short-timescales monitoring and long observations, allowed to deeply investigate the nature of the absorbing medium. The derived distances and physical parameters, typical of BLR clouds, strongly suggest that the X-ray absorber and the clouds responsible for broad emission lines in the optical/UV are at the same distance from the central black hole (see Risaliti 2016 for a review of the X-ray observations of NGC 1365). Recent observations of NGC 1365 with XMM-Newton revealed the presence of a multi-zone warm absorber with different ionization levels (Braito et al 2014).…”

Section: Introductionmentioning

confidence: 91%

XMM–Newton and NuSTAR joint observations of Mrk 915: a deep look into the X-ray properties★

Ballo

Severgnini

Ceca

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We report on the X-ray monitoring programme (covering slightly more than 11 days) carried out jointly by XMM-Newton and NuSTAR on the intermediate Seyfert galaxy Mrk 915. The light curves extracted in different energy ranges show a variation in intensity but not a significant change in spectral shape. The X-ray spectra reveal the presence of a two-phase warm absorber: a fully covering mildly ionized structure [log ξ/(ergs cm s −1 ) ∼ 2.3, N H ∼ 1.3 × 10 21 cm −2 ] and a partial covering (∼ 90 per cent) lower ionized one [log ξ/(ergs cm s −1 ) ∼ 0.6, N H ∼ 2 × 10 22 cm −2 ]. A reflection component from distant matter is also present. Finally, a high-column density (N H ∼ 1.5 × 10 23 cm −2 ) distribution of neutral matter covering a small fraction of the central region is observed, almost constant, in all observations. Main driver of the variations observed between the datasets is a decrease in the intrinsic emission by a factor of ∼ 1.5. Slight variations in the partial covering ionized absorber are detected, while the data are consistent with no variation of the total covering absorber. The most likely interpretation of the present data locates this complex absorber closer to the central source than the narrow line region, possibly in the broad line region, in the innermost part of the torus, or in between. The neutral obscurer may either be part of this same stratified structure or associated with the walls of the torus, grazed (and partially intercepting) the line of sight.

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“…Thanks to the combination of the high spectral and spatial resolution of the Chandra data we have gained more insight in the structure for the circum-nuclear emitter/absorbers of NGC 7582. As seen in other well studied nearby Seyfert 2s and in particular for the prototype of the "Changing look" AGN NGC 1365 (Braito et al 2014;Nardini et al 2015b;Rivers et al 2015a;Risaliti 2016), it is now clear that also in NGC 7582 the absorbing/emitting circum-nuclear gas is not a single homogeneous gas but it is most likely a multiphase medium, located at different distances from the sub-pc BLR region to the larger scale galactic absorber.…”

Section: Discussionmentioning

confidence: 78%

A high spectral resolution map of the nuclear emitting regions of NGC 7582

Braito

Reeves

Bianchi

et al. 2017

A&A

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We present the results of the spatial and spectral analysis of the high resolution data of NGC 7582 that were collected with a deep (∼ 200 ksec) Chandra HETG observation. NGC 7582 is a well studied "changing look" AGN where multiple and possibly clumpy absorbers are present. During this long Chandra observation NGC 7582 was in a highly obscured state. Therefore, we considered also a short (∼ 24 ks) Suzaku observation performed in September 2007, which caught NGC 7582 in a Compton thick state. This allows us to determine the underlying continuum model and the amount of absorption [N H = (1.2 ± 0.2) × 10 24 cm −2 ]. A wealth of emission lines (from Mg, Si, S and Fe) are detected in the Chandra spectrum, which allow us to map the structure of the circumnuclear emitters. The high resolution spectrum reveals that the soft X-ray emission originates in a hybrid gas, which is ionized in part by the strong circum-nuclear star forming activity and in part by the central AGN. The new high resolution images confirm that the emitting region is highly inhomogeneous and extends up to a few hundred pc from the nuclear source. The X-ray images are more extended in the lower energy lines (Ne and Mg) than in the higher energy lines (Si, Fe), where the former are dominated by the collisionally ionised gas from the starburst and the latter by the photoionized AGN emission. This is supported by the analysis of the He-like triplets in the grating spectra, where Mg xi displays strong resonance line emission (starburst) and where Si xiii shows strong forbidden line emission (AGN). We deduce that a low density (n e ∼ 0.3 − 1 cm −3 ) photoionized gas is responsible for the strong forbidden components and although it is more compact than the Ne and Mg emission, it is likely to originate from extended AGN Narrow Line Region gas at distances of 200-300 pc from the black hole. We also detected an absorption feature at ∼ 6.7 keV consistent with the rest frame energy of the 1s − 2p resonance absorption line from Fe xxv (E lab = 6.7 keV), which traces the presence of a sub-parsec scale ionized circumnuclear absorber. The emerging picture is in agreement with our new view of the circumnuclear gas in AGN, where the medium is clumpy and stratified in both density and ionization. These absorbers and emitters are located on different scales: from the sub-pc Broad Line Region gas out to the kpc scale of the galactic absorber.

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Absorption from a multi‐layer circumnuclear medium and reflection from the accretion disc in NGC 1365

Cited by 5 publications

References 14 publications

Testing the accuracy of reflection-based supermassive black hole spin measurements in AGN

Testing the accuracy of reflection-based supermassive black hole spin measurements in AGN

XMM–Newton and NuSTAR joint observations of Mrk 915: a deep look into the X-ray properties★

A high spectral resolution map of the nuclear emitting regions of NGC 7582

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