Relativistic reflection in the average X-ray spectrum of active galactic nuclei in the Véron-Cetty and Véron catalogue

Falocco, S.; Carrera, Francisco J.; Barcons, X.; Miniutti, G.; Corral, A.

doi:10.1051/0004-6361/201322812

Cited by 20 publications

(21 citation statements)

References 35 publications

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“…A broad line profile was seen in the previous X-ray spectral stacking studies of AGN (e.g. Streblyanska et al 2005;Corral et al 2008;Iwasawa et al 2012;Falocco et al 2014;, although typically with low significance. The broad Fe Kα line, which is generally thought to be broadened due to the strong gravitational field of the central SMBH, can be used to constrain the spin of BH (Brenneman & Reynolds 2006;Dauser et al 2010).…”

Section: Non-detection Of the Broad Line In The Bh Mass Sub-samples?mentioning

confidence: 66%

X-ray spectral properties of the AGN sample in the northern XMM-XXL field

Zhu¹,

Merloni²,

Georgakakis³

et al. 2016

Mon. Not. R. Astron. Soc.

147

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In this paper we describe and publicly release a catalogue consisting of 8445 point-like X-ray sources detected in the XMM-XXL north survey. For the 2512 AGN which have reliable spectroscopy from SDSS-III/BOSS, we present the X-ray spectral fitting which has been computed with a Bayesian approach. We have also applied an X-ray spectral stacking method to different sub-samples, selected on the basis of the AGN physical properties (L 2−10 keV , z, M BH , λ Edd and N H ). We confirm the well-known Iwasawa-Taniguchi effect in our luminosityredshift sub-samples, and argue that such an effect is due to a decrease in the covering factor of a distant obscuring 'torus' with increasing X-ray luminosity. By comparing the distribution of the reflection fraction, the ratio of the normalization of the reflected component to the direct radiation, we find that the low-luminosity, low-redshift sub-sample had systematically higher reflection fraction values than the high-redshift, high-luminosity one. On the other hand, no significant difference is found between samples having similar luminosity but different redshift, suggesting that the structure of the torus does not evolve strongly with redshift. Contrary to previous works, we do not find evidence for an increasing photon index at high Eddington ratio. This may be an indication that the structure of the accretion disc changes as the Eddington ratio approaches unity. Comparing our X-ray spectral analysis results with the optical spectral classification, we find that ∼ 20 per cent of optical type-1 AGN show an X-ray absorbing column density higher than 10 21.5 cm −2 , and about 50 per cent of type-2 AGN have an X-ray absorbing column density less than 10 21.5 cm −2 . We suggest that the excess X-ray absorption shown in the high-luminosity optical type-1 AGN can be due to small-scale dustfree gas within (or close to) the broad line region, while in the low-luminosity ones it can be due to a clumpy torus with a large covering factor.

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Section: Non-detection Of the Broad Line In The Bh Mass Sub-samples?mentioning

confidence: 66%

X-ray spectral properties of the AGN sample in the northern XMM-XXL field

Zhu¹,

Merloni²,

Georgakakis³

et al. 2016

Mon. Not. R. Astron. Soc.

147

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“…Substantial line broadening of Fe K emission, most likely due to the relativistic effects at inner radii of the accretion disc, in distant AGN have been studied by many authors using spectral stacking (Streblyanska et al 2005;Brusa et al 2005;Corral et al 2008;Chaudhary et al 2012;Iwasawa et al 2012b;Falocco et al 2013Falocco et al , 2014. Results vary between the works but some evidence of line broadening has been found.…”

Section: Fe K Emission Linesmentioning

confidence: 99%

The XMM deep survey in the CDFS

Iwasawa

Comastri²,

Vignali

et al. 2020

A&A

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We present the X-ray spectra of 185 bright sources detected in the XMM-Newton deep survey of the Chandra Deep Field South with the three EPIC cameras combined. The 2–10 keV flux limit of the sample is 2 × 10−15 erg s−1 cm−2. The sources are distributed over a redshift range of z = 0.1−3.8, with 11 new X-ray redshift measurements included. A spectral analysis was performed using a simple model to obtain absorbing column densities, rest-frame 2–10 keV luminosities, and Fe K line properties of 180 sources at z > 0.4. Obscured AGN are found to be more abundant toward higher redshifts. Using the XMM-Newton data alone, seven Compton-thick AGN candidates were identified, which set the Compton-thick AGN fraction at ≃4%. An exploratory spectral inspection method with two rest-frame X-ray colours and an Fe line strength indicator was introduced and tested against the results from spectral fitting. This method works reasonably well to characterise a spectral shape and can be useful for a pre-selection of Compton-thick AGN candidates. We found six objects exhibiting broad Fe K lines out of 21 unobscured AGN of best data quality, implying a detection rate of ∼30%. Five redshift spikes, each with more than six sources, are identified in the redshift distribution of the X-ray sources. Contrary to the overall trend, the sources at the two higher redshift spikes, at z = 1.61 and z = 2.57, exhibit a puzzlingly low obscuration.

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“…The spectra from the MOS1 and MOS2 instruments were merged with a similar procedure as in Falocco et al (2014). The merging procedure computes the sum of the exposures and the counts, while the backscale is the exposure-weighted average of the backscales of the individual spectra.…”

Section: Mosmentioning

confidence: 99%

Accretion and jets in a low-luminosity AGN: the nucleus of NGC 1052

Falocco

Larsson

Nandi

2020

A&A

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Aims. We aim to determine the properties of the central region of NGC 1052 using X-ray and radio data. NGC 1052 (z=0.005) has been investigated for decades in different energy bands and shows radio lobes and a low luminosity active galactic nucleus (LLAGN). Methods. We use X-ray images from Chandra and radio images from Very Large Array (VLA) to explore the morphology of the central area. We also study the spectra of the nucleus and the surrounding region using observations from Chandra and XMM-Newton. Results. We find diffuse soft X-ray radiation and hotspots along the radio lobes. The spectrum of the circum-nuclear region is well described by a thermal plasma (T∼ 0.6 keV) and a power law with photon index Γ ∼ 2.3. The nucleus shows a hard power law (Γ ∼ 1.4) modified by complex absorption. A narrow iron Kα line is also clearly detected in all observations, but there is no evidence for relativistic reflection. Conclusions.The extended emission is consistent with originating from extended jets and from jet-triggered shocks in the surrounding medium. The hard power-law emission from the nucleus and the lack of relativistic reflection supports the scenario of inefficient accretion in an Advection Dominated Accretion Flow (ADAF).

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Relativistic reflection in the average X-ray spectrum of active galactic nuclei in the Véron-Cetty and Véron catalogue

Cited by 20 publications

References 35 publications

X-ray spectral properties of the AGN sample in the northern XMM-XXL field

X-ray spectral properties of the AGN sample in the northern XMM-XXL field

The XMM deep survey in the CDFS

Accretion and jets in a low-luminosity AGN: the nucleus of NGC 1052

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