THREE-YEAR<i>SWIFT</i>-BAT SURVEY OF ACTIVE GALACTIC NUCLEI: RECONCILING THEORY AND OBSERVATIONS?

Burlon, D.; Ajello, M.; Greiner, J.; Comastri, A.; Merloni, A.; Gehrels, N.

doi:10.1088/0004-637x/728/1/58

Cited by 350 publications

(693 citation statements)

References 114 publications

(139 reference statements)

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“…Indeed, several authors report a decrease in the absorbed AGN population with source luminosity (e.g., Lawrence & Elvis 1982;Steffen et al 2003;La Franca et al 2005;Sazonov et al 2007;Della Ceca et al 2008;Burlon et al 2011) and an increase with redshift at fixed X-ray luminosity (e.g., La Franca et al 2005;Ballantyne et al 2006;Treister & Urry 2006;Ueda et al 2014;Vito et al 2014). Our spectral analysis effectively probes rest-frame 1.2 24 keṼ -for all the sources, given the redshift distribution from z 0  up to z 1.5 » .…”

Section: Fraction Of Absorbed Sourcesmentioning

confidence: 74%

“…-) 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 resulting sample of 63 sources is the focus of the following analysis. The redshift distribution is reported in the right panel of Figure 2, compared to the distribution of the 199 local sources detected by Swift-BAT in the energy range 15-55 keV (Burlon et al 2011). NuSTAR, with its two orders of magnitude greater sensitivity, probes sources well beyond the local universe.…”

Section: Selected Samplementioning

confidence: 99%

“…The horizontal dashed line indicates the threshold value of 7 10 erg s cm 14 1 2 ---defining our sample. Right panel: spectroscopic redshift distribution of our sample (open histogram) compared to the the 199 local sources studied by Swift-BAT in Burlon et al (2011; dark gray, with normalization and histogram binning rescaled by a factor of 10). The arrow indicates the median redshift value for the sample ( z 0.58 á ñ = ) and the light gray region shows the interquartile range.…”

Section: Nustarmentioning

confidence: 99%

“…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). Indeed, the large diversity in the spectral shapes, as well as poorly explored observational parameters in low counting regimes 26 such as the high energy cut-off and the reflection strength at high energies (Treister et al 2009;Ballantyne et al 2011, hereafter BA11), the scattered fractions at low energies (Brightman & Ueda 2012;Lanzuisi et al 2015), or physical parameters such as the Eddington ratio (Draper & Ballantyne 2010), may further introduce uncertainty or biases, enlarging the possible range of the fraction of CT sources to an order of magnitude (Akylas et al 2012) or even significantly reducing their importance (Gandhi et al 2007).…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Fraction Of Absorbed Sourcesmentioning

confidence: 74%

Section: Introductionmentioning

confidence: 93%

Section: Selected Samplementioning

confidence: 99%

Section: Nustarmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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Cosmic X‐ray surveys of active galactic nuclei: The synergy between X‐ray and infrared observations

Alexander

2017

Astron Nachr

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We briefly review the synergy between X-ray and infrared observations for active galactic nuclei (AGNs) detected in cosmic X-ray surveys, primarily with XMM-Newton, Chandra, and NuSTAR. We focus on two complementary aspects of this X-ray-infrared synergy: (a) the identification of the most heavily obscured AGNs, and (b) the connection between star formation and AGN activity. We also briefly discuss future prospects for X-ray-infrared studies over the next decade.

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X‐ray selection of Compton‐Thick AGN at high redshift

Lanzuisi

2017

Astron Nachr

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Compton-Thick (CT) active galactic nuclei (AGN) are a key ingredient of cosmic X-ray background (CXB) synthesis models, but are still an elusive component of the AGN population beyond the local universe. Multiwavelength surveys are the only way to find them at z > ∼ 0.1, and a deep X-ray coverage is crucial in order to clearly identify them among star-forming galaxies. As an example, the deep and wide COSMOS survey allowed us to select a total of 34 CT sources. This number is computed from the 64 nominal CT candidates, each counted for its N H probability distribution function. For each of these sources, rich multiwavelength information is available, which is used to confirm their obscured nature by comparing the expected AGN luminosity from spectral energy distribution fitting with the absorption-corrected X-ray luminosity. While Chandra is more efficient, for a given exposure, in detecting CT candidates in current surveys (by a factor ∼ 2), deep XMM-Newton pointings of bright sources are vital to fully characterize their properties, for example, N H distribution above 10 25 cm − 2 , reflection intensity, etc., all crucial parameters of CXB models. Since luminous CT AGN at high redshift are extremely rare, the future of CT studies at high redshift will have to rely on the large-area surveys currently under way, such as XMM-XXL and Stripe82, and will then require dedicated follow-up with XMM-Newton, while waiting for the advent of the ESA mission Athena.

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THREE-YEARSWIFT-BAT SURVEY OF ACTIVE GALACTIC NUCLEI: RECONCILING THEORY AND OBSERVATIONS?

Cited by 350 publications

References 114 publications

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

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

Cosmic X‐ray surveys of active galactic nuclei: The synergy between X‐ray and infrared observations

X‐ray selection of Compton‐Thick AGN at high redshift

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