Resolving the extragalactic hard X-ray background

Mushotzky, R. F.; Cowie, L. L.; Barger, A. J.; Arnaud, Keith A.

doi:10.1038/35006564

Cited by 419 publications

(566 citation statements)

References 32 publications

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“…The average hardening of faint sources agrees with the shape of the CXB in approximately the same energy range (Marshall et al 1980), as already found at lower energies (e.g., Mushotzky et al 2000;Brandt et al 2001;Giacconi et al 2001). There is one notable outlier with a negative Γ valuethe CT thick source in the COSMOS field reported by C15 (cosmos330 in Table 2).…”

Section: Nustar Spectral Analysissupporting

confidence: 83%

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: Nustar Spectral Analysissupporting

confidence: 83%

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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“…The table reports the source densities per deg2 measured in the central chip (S3) of RX J0030 and 3C 295 for two di †erent Ñux limits (1.5 and 3 ] 10~15 ergs cm~2 s~1) for the 0.5È2 keV detections and for 2 ] 10~14 ergs cm~2 s~1 for the 2È10 keV detections. For comparison, we also report in the same table the log N-log S obtained from the ROSAT Lockman Hole deep Ðeld , two recent Chandra deep Ðelds (Mushotzky et al 2000 ;Giacconi et al 2000), and from the two comparison Ðelds. The log N-log S curves (upper panel of Fig.…”

Section: Densities Of the Serendipitous Sourcesmentioning

confidence: 99%

BeppoSAXObservations of the Maser Seyfert 2 Galaxy ESO 103‐G35

Wilkes

Mathur

Fiore³

et al. 2001

ApJ

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We present results from a Chandra X-Ray Observatory study of the Ðeld X-ray source populations in four di †erent observations : two high-redshift (z D 0.5) clusters of galaxies 3C 295 and RX J003033.2]261819 ; and two noncluster Ðelds with similar exposure time. Surprisingly, the 0.5È2 keV source surface densities (D900È1200 sources deg~2 at a Ñux limit of 1.5 ] 10~15 ergs cm~2 s~1) measured in an D8@ ] 8@ area surrounding each cluster exceed by a factor of D2 the value expected on the basis of the ROSAT and Chandra log N-log S, with a signiÐcance of D2 p each, or D3.5 p when the two Ðelds are combined (i.e., a probability to be a statistical Ñuctuation of \1% and \0.04%, respectively). The same analysis performed on the noncluster Ðelds and on the outer chips of the cluster Ðelds does not show evidence of such an excess. In both cluster Ðelds, the summed 0.5È10 keV spectrum of the detected objects is well Ðtted by a power law with ! D 1.7 similar to active galactic nuclei (AGNs) and shows no sign of intrinsic absorption. The few (D10 of 35) optical identiÐcations available to date conÐrm that most of them are, as expected, AGNs, but the number of redshifts available is too small to allow conclusions on their nature. We discuss possible interpretations of the overdensity in terms of a statistical variation of cosmic background sources ; a concentration of AGNs and/or powerful starburst galaxies associated with the clusters ; and gravitational lensing of background QSOs by the galaxy clusters. All explanations, however, are difficult to reconcile with the large number of excess sources detected. Deeper X-ray observations and more redshifts measurements are clearly required to settle the issue.

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“…These identifications accounted for about 30% of the 2-10 keV hard X-ray background (Ueda et al 1998;Fiore et al 1999). Recently, the new generation of X-ray satellites such as Chandra and XMM-Newton have reached fluxes 100 times fainter, identifying hundreds of sources and almost resolving the hard (2-10 keV) X-ray background (e.g., Mushotzky et al 2000;Fiore et al 2000;Giacconi et al 2001;Hornschemeier et al 2001;Hasinger et al 2001;Tozzi et al 2001;Baldi et al 2002).…”

Section: Introductionmentioning

confidence: 99%

TheBeppoSAXHigh‐Energy Large‐Area Survey. V. The Nature of the Hard X‐Ray Source Population and Its Evolution

Franca

Fiore

Vignali

et al. 2002

ApJ

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We present optical spectroscopic identifications of hard X-ray (5-10 keV) selected sources belonging to the High-Energy Large-Area Survey sample obtained with BeppoSAX down to a 5-10 keV flux limit of f 5 10 keV $ 3 Â 10 À14 ergs cm À2 s À1 . The sample consists of 118 sources. There are 25 sources that have been identified through correlations with catalogs of known sources. A spectroscopic identification for 49 more has been searched for with the telescope. The results of 13 fields were empty down to R ¼ 21. There were 37 sources identified as type 1 active galactic nuclei (AGNs) and nine as type 2 AGNs. The remaining sources are five narrow emission-line galaxies, six clusters, two BL Lac objects, one radio galaxy, and one star. Combining these objects with other hard X-ray selected AGNs from ASCA and HEAO 1, we find that the local luminosity function of type 1 AGNs (AGN 1s) in the 2-10 keV band is fairly well represented by a double power law function. There is evidence for significant cosmological evolution according to a pure luminosity evolution (PLE) model [L X ðzÞ / ð1 þ zÞ k ], with k ¼ 2:12 and 2.22 ( k ' 0:14) in a ð m ; Þ ¼ ð1:0; 0:0Þ and a ð m ; Þ ¼ ð0:3; 0:7Þ cosmology, respectively. The data show an excess of faint high-redshift type AGN 1s, which is well modeled by a luminosity-dependent density evolution (LDDE), similar to what is observed in soft X-rays. However, in both cosmologies, the statistics are not significant enough to distinguish between the PLE and LDDE models. The fitted models imply a contribution of AGN 1s to the 2-10 keV X-ray background from 35% up to 60%.

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Resolving the extragalactic hard X-ray background

Cited by 419 publications

References 32 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

BeppoSAXObservations of the Maser Seyfert 2 Galaxy ESO 103‐G35

TheBeppoSAXHigh‐Energy Large‐Area Survey. V. The Nature of the Hard X‐Ray Source Population and Its Evolution

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