Cosmic X‐Ray Background and Earth Albedo Spectra with<i>Swift</i>BAT

Ajello, M.; Greiner, J.; Sato, G.; Willis, D. R.; Kanbach, G.; Strong, A. W.; Diehl, R.; Hasinger, G.; Gehrels, N.; Markwardt, C. B.; Tueller, J.

doi:10.1086/592595

Cited by 219 publications

(277 citation statements)

References 35 publications

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“…The model used is a combination of our best-fit models for the average spectra of the different classes of objects (AB and LOB), normalizing their ratio using the N H distribution of Treister et al (2009). We also show the data obtained by INTEGRAL JEM-X (stars, Türler et al 2010) and Swift BAT (triangles, Ajello et al 2008b) above 10 keV.…”

Section: The Cosmic X-ray Backgroundmentioning

confidence: 99%

Reflection in Seyfert galaxies and the unified model of AGN

Ricci

Walter

Courvoisier

et al. 2011

A&A

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We present a deep study of the average hard X-ray spectra of Seyfert galaxies. We aim to test the unified model of active galactic nuclei, and constrain differences and similarities between different classes of objects. We analyzed all public INTEGRAL IBIS/ISGRI data available on all the 165 Seyfert galaxies detected at z < 0.2. Our final sample consists of 44 Seyfert 1s, 29 Seyfert 1.5s, 78 Seyfert 2s, and 14 narrow-line Seyfert 1s. For each subsample, we stacked all the images, and derived their average hard X-ray spectra in the 17-250 keV energy range. We performed a detailed spectral analysis using both a model-independent and a model-dependent approach. All classes of Seyfert galaxies show on average the same nuclear continuum, as foreseen by the zeroth order unified model, with a cutoff energy of E C 200 keV, and a photon index of Γ ≃ 1.8. The average optical depth of the Comptonizing medium is consistent for the different classes (τ ≃ 0.8). Compton-thin Seyfert 2s show a reflection component stronger than Seyfert 1s and Seyfert 1.5s. Most of this reflection is due to mildly obscured (10 23 cm −2 ≤ N H < 10 24 cm −2 ) Seyfert 2s, which have a significantly stronger reflection component (R = 2.2 +4.5 −1.1 ) than Seyfert 1s (R ≤ 0.4), Seyfert 1.5s (R ≤ 0.4) and lightly obscured (N H < 10 23 cm −2 ) Seyfert 2s (R ≤ 0.5). This cannot be explained easily by the unified model. The absorber/reflector in mildly obscured Seyfert 2s might cover a large fraction of the X-ray source, and contain clumps of Compton-thick material. The large reflection found in the spectrum of mildly obscured Seyfert 2s reduces the amount of Compton-thick objects needed to explain the peak of the cosmic X-ray background. Our results are consistent with the fraction of Compton-thick sources being ∼ 10%. The spectra of Seyfert 2s with and without polarized broad lines do not show significant differences, the only difference between the two samples being the higher hard X-ray and bolometric luminosity of Seyfert 2s with polarized broad lines. The average hard X-ray spectrum of narrow-line Seyfert 1s is steeper than those of Seyfert 1s and Seyfert 1.5s, probably due to a lower energy of the cutoff.

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Section: The Cosmic X-ray Backgroundmentioning

confidence: 99%

Reflection in Seyfert galaxies and the unified model of AGN

Ricci

Walter

Courvoisier

et al. 2011

A&A

129

143

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“…They all give approximately the correct relic density. Observations from soft X-rays to gamma-rays are marked with red to violet, following approximately a rainbow color pattern: red symbols [46], red arrows (Chandra, [33]), orange symbols (INTEGRAL, [47]), yellow symbols (SWIFT BAT, [32]), yellow arrows [48], green area (SMM, [49]), light blue (COMPTEL, [50]), blue (EGRET, [51]), violet (Fermi-LAT, [52]), violet arrows [34,35]. The points with error bars are absolute measurements with 2σ or 1σ errors.…”

Section: Extragalactic Cdmabmentioning

confidence: 99%

“…We take the absolute measurements obtained using the latter two satellites according to the analysis of [46] (red symbols in Fig. 2), [47] (orange symbols) and [32] (yellow symbols). At intermediate energies, 300 keV ≤ E 0 ≤ 30 MeV, the measurements come from the Solar Maximum Mission (SMM) [49] and COMPTEL [50].…”

Section: A Observationsmentioning

confidence: 99%

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Cosmic X-ray and gamma-ray background from dark matter annihilation

et al. 2011

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The extragalactic background light (EBL) observed at multiple wavelengths is a promising tool to probe the nature of dark matter. This radiation might contain a significant contribution from gamma-rays produced promptly by dark matter particle annihilation in the many halos and subhalos within our past-light cone. Additionally, the electrons and positrons produced in the annihilation give energy to the cosmic microwave photons to populate the EBL with X-rays and gamma-rays.To study these signals, we create full-sky maps of the expected radiation from both of these contributions using the high-resolution Millennium-II simulation of cosmic structure formation. Our method also accounts for a possible enhancement of the annihilation rate by a Sommerfeld mechanism due to a Yukawa interaction between the dark matter particles prior to annihilation. We use upper limits on the contributions of unknown sources to the EBL to constrain the intrinsic properties of dark matter using a model-independent approach that can be employed as a template to test different particle physics models. These upper limits are based on observational measurements spanning eight orders of magnitude in energy (from soft X-rays measured by the CHANDRA satellite to gamma-rays measured by the Fermi satellite), and on expectations for the contributions from non-blazar active galactic nuclei, blazars and star forming galaxies. To exemplify this approach, we analyze a set of benchmark Sommerfeld-enhanced models that give the correct abundance of dark matter, satisfy constraints from the cosmic microwave background, and fit the cosmic ray spectra measured by PAMELA and Fermi without any contribution from local substructure. We find that these models are in conflict with the EBL constraints unless the contribution of unresolved substructure is small and the dark matter annihilation signal dominates the EBL. We conclude that provided the collisionless cold dark matter paradigm is accurate, even for conservative estimates of the contribution from unresolved substructure and astrophysical backgrounds, the EBL is at least as sensitive a probe of these types of scenarios as the cosmic microwave background. More generally, our results disfavor an explanation of the positron excess measured by the PAMELA satellite based only on dark matter annihilation in the smooth Galactic dark matter halo.PACS numbers: 95.35.+d,95.85.Nv,95.85.Pw

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“…Ajello2008 [16] is another recent model with a smoothly joined double power law. It was obtained by fitting the data in the 2 keV-2 MeV range.…”

Section: Cosmic Gamma-ray Background Modelmentioning

confidence: 99%

Influence of the Earth on the background and the sensitivity of the GRM and ECLAIRs instruments aboard the Chinese-French mission SVOM

et al. 2012

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SVOM (Space-based multi-band astronomical Variable Object Monitor) is a future Chinese-French satellite mission which is dedicated to GammaRay Burst (GRB) studies. Its anti-solar pointing strategy makes the Earth cross the field of view of its payload every orbit. In this paper, we present the variations of the gamma-ray background of the two high energy instruments aboard SVOM, the Gamma-Ray Monitor (GRM) and ECLAIRs, as a function of the Earth position. We conclude with an estimate of the Earth influence on their sensitivity and their GRB detection capability.

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Cosmic X‐Ray Background and Earth Albedo Spectra withSwiftBAT

Cited by 219 publications

References 35 publications

Reflection in Seyfert galaxies and the unified model of AGN

Reflection in Seyfert galaxies and the unified model of AGN

Cosmic X-ray and gamma-ray background from dark matter annihilation

Influence of the Earth on the background and the sensitivity of the GRM and ECLAIRs instruments aboard the Chinese-French mission SVOM

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