The dust-gas AGN torus as constrained from X-ray and mid-infrared observations

Esparza-Arredondo, Donají; González‐Martín, O.; Dultzin, D.; Masegosa, J.; Almeida, C. Ramos; García-Bernete, I.; Fritz, J.; Osorio-Clavijo, Natalia

doi:10.1051/0004-6361/202040043

“…5 can be seen that our results, when compared with previous studies, seem to agree with the correlations found by Gu & Cao (2009), She et al (2018), and Younes et al (2011), but the effect of the large scatter in previous studies can be appreciated. The same is true for the highaccretion branch, where the relation of Fanali et al (2013) (at log(λ Edd ) > -2.39) fits well the data of Esparza-Arredondo et al (2021).…”

Section: Determination Of the L Bol /L Eddsupporting

confidence: 71%

Constraining the X-ray reflection in low accretion-rate active galactic nuclei using XMM-Newton, NuSTAR, and Swift

Diaz

¹

,

Hernández-García

²

,

Arévalo

³

et al. 2023

A&A

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Context. An interesting feature of active galactic nuclei (AGN) accreting at low rates is the weakness of the reflection features in their X-ray spectra, which may result from the gradual disappearance of the torus with decreasing accretion rates. It has been suggested that low-luminosity AGN (LLAGN) would exhibit a different reflector configuration than high-luminosity AGN, covering a smaller fraction of the sky or simply having less material. Additionally, we note that the determination of the spectral index (Γ) and the cut-off energy of the primary power-law emission is affected by the inclusion of reflection models, showing their importance in studying accretion mechanisms. This is especially valid in the case of the LLAGN which has previously shown a high dispersion in the relation between Γ and the accretion rate. Aims. Our purpose is to constrain the geometry and column density of the reflector in a sample of LLAGN covering a broad X-ray range of energy by combining data from XMM-Newton+ NuSTAR + Swift. The spectral analysis also allows us to investigate the accretion mechanism in LLAGN. Methods. We used XMM-Newton+ NuSTAR + Swift observations of a hard X-ray flux-limited sample of 17 LLAGN from BASS/DR2 with accretion rates of λ Edd =L Bol /L Edd <10 −3 . We fit all spectra using the reflection model for torus (BORUS) and accretion disk (XILLVER) reflectors. Results. We found a tentative correlation between the torus column density and the accretion rate, with LLAGN showing a lower column density than the high-luminosity objects. We also confirm the relation between Γ and λ Edd , with a smaller scatter than previously reported, thanks to the inclusion of high-energy data and the reflection models. Our results are consistent with a break at λ Edd ∼ 10 −3 , which is suggestive of a different accretion mechanism compared with higher accretion AGN.

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“…Ricci et al 2011 ;Liu & Li 2014 ;Ricci et al 2014 ;Furui et al 2016 ;Kawamuro et al 2016 ), but also thanks to the unprecedented sensitivity achieved above 10 keV provided by NuSTAR (e.g. Esparza-Arredondo et al 2019, 2021Panagiotou & Walter 2019.…”

Section: Introductionmentioning

confidence: 99%

Observational hints on the torus obscuring gas behaviour through X-rays with NuSTAR data

Osorio-Clavijo¹,

González‐Martín²,

Sánchez-Sánchez

³

et al. 2021

Monthly Notices of the Royal Astronomical Society

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According to theory, the torus of active galactic nuclei (AGN) is sustained from a wind coming off the accretion disk, and for low efficient AGN, it has been proposed that such structure disappears. However, the exact conditions for its disappearance remain unclear. This can be studied throughout the reflection component at X-rays, which is associated with distant and neutral material at the inner walls of the torus in obscured AGN. We select a sample of 81 AGNs observed with NuSTAR with a distance limit of D< 200 Mpc and Eddington rate $\rm {\lambda _{Edd} \equiv L_{bol}/L_{Edd}<10^{-3}}$. We fit the 3-70 keV spectra using a model accounting for a partial-covering absorber plus a reflection component from neutral material. We find that the existence of the reflection component spans in a wide range of black hole mass and bolometric luminosities, with only ∼13 per cent of our sample (11 sources) lacking of any reflection signatures. These sources fall in the region in which the torus may be lacking in the L-MBH diagram. For the sources with a detected reflection component, we find that the vast majority of them are highly obscured ($\rm {\log \ N_H > 23}$), with $\rm {\sim 20{{\ \rm per\ cent}}}$ being Compton-thick. We also find an increase on the number of unobscured sources and a tentative increase on the ratio between $\rm {FeK\alpha }$ emission line and Compton-hump luminosities toward $\rm {\lambda _{Edd}=10^{-5}}$, suggesting that the contribution of the $\rm {FeK\alpha }$ line changes with Eddington ratio.

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“…It provides a combination of sensitivity, spatial resolution, and spectral resolution factors of 10-100 improved over previous X-ray satellites in the hard X-ray band (Harrison et al 2013). Recently, NuSTAR has observed a large number of local CTAGNs (e.g., Arévalo et al 2014;Baloković et al 2014;Puccetti et al 2014;Bauer et al 2015;Rivers et al 2015;Guainazzi et al 2016;Koss et al 2016;Puccetti et al 2016;Oda et al 2017;Baloković et al 2018;Marchesi et al 2019aMarchesi et al , 2019bZhao et al 2019aZhao et al , 2019bZhao et al , 2020Zhao et al , 2021Esparza-Arredondo et al 2021).…”

mentioning

confidence: 99%

NuSTAR Observations of 52 Compton-thick Active Galactic Nuclei Selected by the Swift/Burst Alert Telescope All-sky Hard X-Ray Survey

Tanimoto

¹

,

Ueda

²

,

Odaka

³

et al. 2022

ApJS

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We present systematic broadband X-ray spectral analysis of 52 Compton-thick ( 24 ≤ log N H LOS / cm − 2 ) active galactic nucleus (CTAGN) candidates selected by the Swift/Burst Alert Telescope all-sky hard X-ray survey observed with Chandra, X-ray Multi-Mirror Mission-Newton (XMM-Newton), Swift/X-Ray Telescope, Suzaku, and NuSTAR. The XMM-Newton data of 10 objects and the NuSTAR data of 15 objects are published for the first time. We use an X-ray spectral model from a clumpy torus (XClumpy) to determine the torus properties. As a result, the hydrogen column density along the line of sight N H LOS obtained from the XClumpy model indicates that 24 objects are Compton-thin AGNs and 28 objects are CTAGNs in a 90% confidence interval. The main reason is the difference in the torus model applied. The hydrogen column density along the equatorial direction N H Equ of CTAGNs inferred from the XClumpy model is larger than that of less obscured AGNs. The Compton-thin torus covering factor C 22 obtained from the XClumpy model is consistent with that of Ricci et al. in the low Eddington ratio ( log R Edd ≤ − 1.0 ), whereas C 22 inferred from the XClumpy model is larger than that of Ricci et al. in the high Eddington ratio ( − 1.0 ≤ log R Edd ). The average value of the Compton-thick torus covering factor C 24 obtained from the XClumpy model is 36 − 4 + 4 %. This value is larger than that of Ricci et al. ( C 24 ≃ 27 − 4 + 4 %) based on the assumption that all AGNs have intrinsically the same torus structure. These results suggest that the structure of CTAGNs may be intrinsically different from that of less obscured AGNs.

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The dust-gas AGN torus as constrained from X-ray and mid-infrared observations

Cited by 29 publications

References 147 publications

Constraining the X-ray reflection in low accretion-rate active galactic nuclei using XMM-Newton, NuSTAR, and Swift

Constraining the X-ray reflection in low accretion-rate active galactic nuclei using XMM-Newton, NuSTAR, and Swift

Observational hints on the torus obscuring gas behaviour through X-rays with NuSTAR data

NuSTAR Observations of 52 Compton-thick Active Galactic Nuclei Selected by the Swift/Burst Alert Telescope All-sky Hard X-Ray Survey

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