The synthesis of the cosmic X-ray background in the Chandra and XMM-Newton era

Gilli, R.; Comastri, A.; Hasinger, G.

doi:10.1051/0004-6361:20066334

Cited by 935 publications

(1,783 citation statements)

References 103 publications

(257 reference statements)

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supporting

confidence: 86%

“…Nonetheless, this analysis clearly demonstrates the presence of a significant contribution from a reflection component to the X-ray spectrum of this z = 0.658 quasar. The properties of RX J1131-3 1231 are consistent [11,13,12,14,16] with the known observational characteristics of quasars at 0.5 z 1, and our results suggest that the relativistic reflection component from the large population of unobscured quasars expected in this epoch [17] could significantly contribute in the 20-30 keV band of the Cosmic X-ray background.Although questions have previously been raised over whether reflection is a unique interpretation for the features observed in AGNs, the amassed evidence points towards this theoretical framework [24, 29], and reached culmination with the launch of NuSTAR and the strong confirmation of relativistic disk reflection from a rapidly spinning supermassive black hole at the centre of the nearby galaxy NGC 1365 [6]. Nonetheless, there still remain possible systematic uncertainties, for example, due to the intrinsic assumption that the disk truncates at the innermost stable circular orbit.…”

supporting

confidence: 86%

“…We now consider the two "microlensing-active" images, A and D. Ref [16] highlight two periods of distinct behaviour in the evolution of Image-D, one in which the the Fe-Kα line profile appears to show a distinctive peak at ∼ 6.4 keV, which they call Periods 1 and 3 (epochs 1-16 and 23-30 respectively), and the other where the Fe-line region is better described by a double profile during their Period 2 (epochs [17][18][19][20][21][22]. In comparison, they did not see any such evolution from the microlensingquiet period in Image-C. Extended Data Fig.…”

Section: Combined "Microlensing-active" Images-a and Dmentioning

confidence: 96%

“…Quasars located between 0.5 z 1 are considerably more powerful than local Seyferts and are known to be a major contributor to the Cosmic X-ray background [17], making them objects of particular cosmological importance. 1RXS J113151.6-123158 (hereafter RX J1131-1231) is a quadruply imaged quasar at redshift z = 0.658 hosting a supermassive black hole (M BH ∼ 2×10 8 M ⊙ ) [18] gravitationally lensed by an elliptical galaxy at z = 0.295 [19].…”

mentioning

confidence: 99%

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Reflection from the strong gravity regime in a lensed quasar at redshift z = 0.658

Reis

Reynolds

Miller

et al. 2014

Nature

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The co-evolution of a supermassive black hole with its host galaxy[1] through cosmic time is encoded in its spin[2, 3, 4]. At z > 2, supermassive black holes are thought to grow mostly by merger-driven accretion leading to high spin. However, it is unknown whether below z ∼ 1 these black holes continue to grow via coherent accretion or in a chaotic manner [5], though clear differences are predicted [3,4] in their spin evolution. An established method[6] to measure the spin of black holes is via the study of relativistic reflection features [7] from the inner accretion disk. Owing to their greater distances, there has hitherto been no significant detection of relativistic reflection features in a moderateredshift quasar. Here, we use archival data together with a new, deep observation of a gravitationally-lensed quasar at z = 0.658 to rigorously detect and study reflection in this moderate-redshift quasar. The level of relativistic distortion present in this reflection spectrum enables us to constrain the emission to originate within 3 gravitational radii from the black hole, implying a spin parameter a = 0.87 +0.08 −0.15 at the 3σ level of confidence and a > 0.66 at the 5σ level. The high spin found here is indicative of growth via coherent accretion for this black hole, and suggests that black hole growth between 0.5 z 1 occurs principally by coherent rather than chaotic accretion episodes. 1When optically-thick material, e.g. an accretion disc, is irradiated by hard X-rays, some of the flux is reprocessed into an additional 'reflected' emission component, which contains both continuum emission and atomic features. The most prominent signature of reflection from the inner accretion disc is typically the relativistic iron Kα line (6.4-6.97 keV; rest frame) [8] and the Compton reflection hump [7] often peaking at 20 − 30 keV (rest-frame). However, the deep gravitational potential and strong Doppler shifts associated with regions around black holes will also cause the forest of soft X-ray emission lines in the ∼ 0.7 − 2.0 keV range to be blended into a smooth emission feature, providing a natural explanation for the "soft-excess" observed in the X-ray spectra of nearby active galactic nuclei (AGNs) [9,10]. Indeed, both the iron line and the soft excess can be used to provide insight into the nature of the central black hole and to measure its spin [10]. Prior studies have revealed the presence of a soft-excess in 90% of quasars at[11, 12] z 1.7, and broad Fe-lines are also seen in 25% of these objects [11,13], suggesting that reflection is also prevalent in these distant AGNs. However, due to the inadequate S/N resulting from their greater distances, the X-ray spectra of these quasars were necessarily modeled using simple phenomenological parameterizations [12,14].Gravitational lensing offers a rare opportunity to study the innermost relativistic region in distant quasars [15,16], by acting as a natural telescope and magnifying the light from these sources. Quasars located between 0.5 z 1 are considerably ...

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supporting

confidence: 86%

supporting

confidence: 86%

Section: Combined "Microlensing-active" Images-a and Dmentioning

confidence: 96%

mentioning

confidence: 99%

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Reflection from the strong gravity regime in a lensed quasar at redshift z = 0.658

Reis

Reynolds

Miller

et al. 2014

Nature

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“…-) AGN population and further shed light on the known decreasing trend between the numerical relevance of this population compared to all AGN (absorbed fraction) and the source luminosity (Lawrence & Elvis 1982;Gilli et al 2007;Burlon et al 2011;Buchner et al 2015) and its redshift evolution (La Franca et al 2005;Ballantyne et al 2006;Treister & Urry 2006;Aird et al 2015a;Buchner et al 2015;Liu et al 2017). They also allow exploration of the importance of the CT population, although with different constraining power and different non-negligible degrees of bias-especially at the highest column densities and lowest luminosities (e.g., Burlon et al 2011;Brightman et al 2014;Buchner et al 2015;Lanzuisi et al 2015;Ricci et al 2015).…”

Section: Introductionmentioning

confidence: 93%

The NuSTAR Extragalactic Surveys: X-Ray Spectroscopic Analysis of the Bright Hard-band Selected Sample

Zappacosta

Comastri

Civano

et al. 2018

ApJ

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We discuss the spectral analysis of a sample of 63 active galactic nuclei (AGN) detected above a limiting flux of S 8 24 keV 7 10 14 =´-( -) erg s cm 1 2 --in the multi-tiered NuSTAR extragalactic survey program. The sources span a redshift range z 0 2.1 = -(median z 0.58 á ñ = ). The spectral analysis is performed over the broad 0.5-24keV energy range, combining NuSTAR with Chandra and/or XMM-Newton data and employing empirical and physically motivated models. This constitutes the largest sample of AGN selected at 10 keV > to be homogeneously spectrally analyzed at these flux levels. We study the distribution of spectral parameters such as photon index, column density (N H ), reflection parameter (R), and 10-40keV luminosity (L X ). Heavily obscured ( N log cm 23AGN constitute ∼25% (15-17 sources) and ∼2-3% (1-2 sources) of the sample, respectively. The observed N H distribution agrees fairly well with predictions of cosmic X-ray background population-synthesis models (CXBPSM). We estimate the intrinsic fraction of AGN as a function of N H , accounting for the bias against obscured AGN in a flux-selected sample. The fraction of CT AGN relative to N log cm 20 24AGN is poorly constrained, formally in the range 2-56% (90% upper limit of 66%). We derived a fraction ( f abs ) of obscured AGN ( N log cm 22 24as a function of L X in agreement with CXBPSM and previous z 1 < X-ray determinations. Furthermore, f abs at z 0.1 0.5 = -and L log erg s 43.6 44.3agrees with observational measurements/trends obtained over larger redshift intervals. We report a significant anti-correlation of R with L X (confirmed by our companion paper on stacked spectra) with considerable scatter around the median R values.

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