Energy spectrum of diffuse component of cosmic soft γ rays

Fukada, Y.; Hayakawa, Satio; Kasahara, I.; Makino, F.; Tanaka, Yasuo; Sreekantan, B. V.

doi:10.1038/254398a0

Cited by 35 publications

(19 citation statements)

References 10 publications

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“…At 0.25 keV (λ ∼ 50 A) the measurement is taken from Warwick & Roberts (1998) obtained using shadow measurements from ROSAT. The X-ray background measurements are taken from various instruments; Chandra (Cappelluti et al 2017), ASCA (Gendreau et al 1995), HEAO-1 and HEAO-4 (Gruber et al 1999;Kinzer et al 1997), Integral (Churazov et al 2007), RXTE (Revnivtsev et al 2003), Swift/BAT (Ajello et al 2008) and Nagoya balloon (Fukada et al 1975). Similarly γ-ray background measurements are taken from instruments: SMM (Watanabe et al 1997), compton/Comptel (Weidenspointner et al 2000), compton/EGRET (Strong et al 2003) and Fermi/LAT (Ackermann et al 2015).…”

Section: The Ebl Spectrummentioning

confidence: 99%

New synthesis models of consistent extragalactic background light over cosmic time

Khaire

Srianand

2019

Monthly Notices of the Royal Astronomical Society

131

135

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We present new synthesis models of the extragalactic background light (EBL) from far infra-red (FIR) to TeV γ-rays, with an emphasis on the extreme ultraviolet (UV) background which is responsible for the observed ionization and thermal state of the intergalactic medium across the cosmic time. Our models use updated values of the star formation rate density and dust attenuation in galaxies, QSO emissivity, and the distribution of H I gas in the IGM. Two of the most uncertain parameters in these models, the escape fraction of H I ionizing photons from galaxies and the spectral energy distribution (SED) of QSOs, are determined to be consistent with the latest measurements of H I and He II photoionization rates, the He II Lyman-α effective optical depths, various constraints on H I and He II reionization history and many measurements of the local EBL from soft X-rays till γ-rays. We calculate the EBL from FIR to TeV γ-rays by using FIR emissivities from our previous work and constructing an average SED of high-energy emitting QSOs, i.e, type-2 QSOs and blazars. For public use, we also provide the EBL models obtained using different QSO SEDs at extreme-UV energies over a wide range of redshifts. These can be used to quantify uncertainties in the parameters derived from photoionization models and numerical simulations originating from the allowed variations in the UV background radiation.

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Section: The Ebl Spectrummentioning

confidence: 99%

New synthesis models of consistent extragalactic background light over cosmic time

Khaire

Srianand

2019

Monthly Notices of the Royal Astronomical Society

131

135

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“…Spectrum of the CXB and contribution of the FSRQs (blue region). The data points are different measurements of the diffuse background as indicated in the label(Fukada et al 1975;Gendreau et al 1995;Watanabe et al 1997;Weidenspointner et al 2000;Revnivtsev et al 2003;Ajello et al 2008b). The dashed line is the total contribution of Seyfert-like AGNs computed with the model ofGilli et al (2007) arbitrarily multiplied by 1.1 to fit the CXB emission at 30 keV.…”

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confidence: 99%

THE EVOLUTION OFSWIFT/BAT BLAZARS AND THE ORIGIN OF THE MeV BACKGROUND

Ajello

Costamante

Sambruna

et al. 2009

ApJ

222

338

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We use three years of data from the Swift/Burst Alert Telescope (BAT) survey to select a complete sample of X-ray blazars above 15 keV. This sample comprises 26 flat-spectrum radio quasars (FSRQs) and 12 BL Lacertae (BL Lac) objects detected over a redshift range of 0.03 < z < 4.0. We use this sample to determine, for the first time in the 15-55 keV band, the evolution of blazars. We find that, contrary to the Seyfert-like active galactic nuclei (AGNs) detected by BAT, the population of blazars shows strong positive evolution. This evolution is comparable to the evolution of luminous optical quasi-stellar objects (QSOs) and luminous X-rayselected AGNs. We also find evidence for an epoch dependence of the evolution as determined previously for radio-quiet AGNs. We interpret both these findings as a strong link between accretion and jet activity. In our sample, the FSRQs evolve strongly, while our best fit shows that BL Lac objects might not evolve at all. The blazar population accounts for 10%-20% (depending on the evolution of the BL Lac objects) of the cosmic Xray background (CXB) in the 15-55 keV band. We find that FSRQs can explain the entire CXB emission for energies above 500 keV solving the mystery of the generation of the MeV background. The evolution of luminous FSRQs shows a peak in redshift (z c = 4.3 ± 0.5) which is larger than the one observed in QSOs and X-rayselected AGNs. We argue that FSRQs can be used as tracers of massive elliptical galaxies in the early universe.

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“…These populations may contribute to the MeV background as well. However, the background spectrum from several hundreds keV to several tens MeV is smoothly connected to the CXB spectrum and is much softer (photon index Γ ∼ 2.8) than the GeV component (Fukada et al 1975;Watanabe et al 1997;Weidenspointner et al 2000), in-dicating a different origin from that above 100 MeV (e.g. Sreekumar et al 1998;Abdo et al 2010a).…”

Section: Introductionmentioning

confidence: 99%

PROBING THE COSMIC X-RAY AND MeV GAMMA-RAY BACKGROUND RADIATION THROUGH THE ANISOTROPY

Inoue

Murase

Madejski

et al. 2013

ApJ

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While the cosmic soft X-ray background is very likely to originate from individual Seyfert galaxies, the origin of the cosmic hard X-ray and MeV gamma-ray background is not fully understood. It is expected that Seyferts including Compton thick population may explain the cosmic hard X-ray background. At MeV energy range, Seyferts having non-thermal electrons in coronae above accretion disks or MeV blazars may explain the background radiation. We propose that future measurements of the angular power spectra of anisotropy of the cosmic X-ray and MeV gamma-ray backgrounds will be key to deciphering these backgrounds and the evolution of active galactic nuclei (AGNs). As AGNs trace the cosmic large-scale structure, spatial clustering of AGNs exists. We show that e-ROSITA will clearly detect the correlation signal of unresolved Seyferts at 0.5-2 keV and 2-10 keV bands and will be able to measure the bias parameter of AGNs at both bands. Once the future hard X-ray all sky satellites achieve the sensitivity better than 10 −12 erg/cm 2 /s at 10-30 keV or 30-50 keV -although this is beyond the sensitivities of current hard X-ray all sky monitors -angular power spectra will allow us to independently investigate the fraction of Compton-thick AGNs in all Seyferts. We also find that the expected angular power spectra of Seyferts and blazars in the MeV range are different by about an order of magnitude, where the Poisson term, so-called shot noise, is dominant. Current and future MeV instruments will clearly disentangle the origin of the MeV gamma-ray background through the angular power spectrum.

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Energy spectrum of diffuse component of cosmic soft γ rays

Cited by 35 publications

References 10 publications

New synthesis models of consistent extragalactic background light over cosmic time

New synthesis models of consistent extragalactic background light over cosmic time

THE EVOLUTION OFSWIFT/BAT BLAZARS AND THE ORIGIN OF THE MeV BACKGROUND

PROBING THE COSMIC X-RAY AND MeV GAMMA-RAY BACKGROUND RADIATION THROUGH THE ANISOTROPY

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