A low level of extragalactic background light as revealed by γ-rays from blazars

By F. Aharonian, A. Akhperjanian, A. R. Bazer-Bachi, M. Beilicke, W. Benbow, D. Berge, K. Bernlöhr, Catherine Boisson, O. Bolz, V. Borrel and 92 more. Nature, 2005

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The diffuse extragalactic background light consists of the sum of the starlight emitted by galaxies through the history of the Universe, and it could also have an important contribution from the ‘first stars’, which may have formed before galaxy formation began. Direct measurements are difficult and not yet conclusive, owing to the large uncertainties caused by the bright foreground emission associated with zodiacal light. An alternative approach is to study the absorption features imprinted on the γ-ray spectra of distant extragalactic objects by interactions of those photons with the background light photons. Here we report the discovery of γ-ray emission from the blazars H 2356 - 309 and 1ES 1101 - 232, at redshifts z = 0.165 and z = 0.186, respectively. Their unexpectedly hard spectra provide an upper limit on the background light at optical/near-infrared wavelengths that appears to be very close to the lower limit given by the integrated light of resolved galaxies. The background flux at these wavelengths accordingly seems to be strongly dominated by the direct starlight from galaxies, thus excluding a large contribution from other sources—in particular from the first stars formed. This result also indicates that intergalactic space is more transparent to γ-rays than previously thought.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

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Citations in the corpus

Extragalactic optical-infrared background radiation, its time evolution and the cosmic photon-photon opacity (2008, background): “…Cherenkov telescopes, now operating between a few tens of GeV to tens of TeV (e.g. HEGRA, HESS, MAGIC): particularly debated is how much the TeV observations of distant BLAZARs are, or are not, consistent with the photon-photon absorption eff ct (e.g. Aharonian et al. 2006; Albert et al. 2006).”
The extragalactic background light revisited and the cosmic photon–photon opacity (Corrigendum) (2017, background): “…- and VHE [above 100 GeV]) spectra of sev- eral blazars observed with imaging atmospheric Cherenkov telescopes, now operating between a few tens of GeV to tens of TeV (e.g., HEGRA, HESS, MAGIC, see e.g., Dwek and Slavin 1994, Stanev and Franceschini 1998, Aharonian et al. 2006, Albert et al. 2006).”
Variable Very High Energy γ-Ray Emission from Markarian 501 (2007, methodology): “A correction using the EBL models Aharonian et al. (2006) and and Primack et al. (2005) gave very similar results, while using Kneiske et al. (2004: ’Best’) and Stecker et al. (2006,2007) gave slightly larger energy fluxes above 1 TeV14.”
Swift observations of the very intense flaring activity of Mrk 421 during 2006. I. Phenomenological picture of electron acceleration and predictions for MeV/GeV emission (2009, background): “…that makes the universe more transparent to high-energy radiation than previously assumed, which is consistent with the discovery of HBLs objects at high redshift, such as H 2356-309 (z = 0.165), 1ES 1101-232 (z = 0.186) (Aharonian et al. 2006), and 1ES 128-304 (z = 0.182) (Albert et al. 2006).”
GeV gamma-ray attenuation and the high-redshift UV background (2009, background): “At energies above 100 GeV, the effect of the EBL has often been quantified as a change in the spectral index of observed blazar spectra (e.g. Aharonian et al. 2006), due to the relatively flat number density of EBL photons in the near and mid-IR.”
The power of blazar jets (2007, background): “…(Aharonian et al. 2005a; see C02 and G02); 2155–304 (Aharonian et al. 2005b; Aharonian et al. 2007b; already present in G98 as an EGRET source); 2200+420 (Albertet al. 2007b; already present in G98 as an EGRET source); 2356–309 (Aharonian et al. 2006a; Aharonian et al. 2006c; see C02 and G02).”
Extreme TeV blazars and the intergalactic magnetic field (2010, result): “…Gilmore et al. (2009), Finke et al. (2010), Dominguez et al. (2010), agree well (but see Orr et al. 2011) and are consistent with the low level of the EBL suggested by the rec nt observations of Cherenkov telescopes (e.g. Aharonian et al. 2006, Mazin & Raue 2007; see also Kneiske & Dole 2010).”
THE LARGE AREA TELESCOPE ON THE FERMI GAMMA-RAY SPACE TELESCOPE MISSION (2009, background): “The GCN provides locations of GRBs (the Notices) detected onboard by the LAT or the GBM and reports on follow-up observations (the Circulars and the Reports) made by ground-based and space-based optical, radio x-ray, TeV, and other observers.”
PARTICLE ACCELERATION AND PLASMA DYNAMICS DURING MAGNETIC RECONNECTION IN THE MAGNETICALLY DOMINATED REGIME (2015, methodology): “Hard power laws p ∼ 1 in TeV range have been inferred after removing effect of the extragalactic background light using various models (Aharonian et al. 2006; Krennrich et al. 2008).”
Search for TeV Gamma-ray Emission from GRB 100621A, an extremely bright GRB in X-rays, with H.E.S.S (2014, methodology): “However, blazar observations show that the level of EBL extinction is lower than previously thought (e.g. Aharonian et al. 2006b) and it is possible to detect VHE gamma-ray sources even at redshifts above 0.6 with the current generation of telescopes (Furniss et al. 2013).”
Towards a new generation axion helioscope (2011, background): “[57, 58], and ultra high energy cosmic rays [59, 60] from very distant sources, such as active galactic nuclei.”
Measurement of the extragalactic background light imprint on the spectra of the brightest blazars observed with H.E.S.S. (2012, methodology): “The coincident detection of a shower with at least two telescopes improves the γ/hadron separation (Funk et al. 2004; Aharonian et al. 2006a).”
A lower-limit flux for the extragalactic background light (2010, methodology): “…of 3C279 blazar atz = 0.536 by the MAGIC collaboration (Albert et al. (2008), Errando et al. (2009)) has arisen the qu stion of the transparency of the Universe to theγ-rays, and the level of the Cosmic Infrared Background (e.g.Aharonian et al. 2006, Aharonian et al. 2007a, Stecker & Scully 2009).”
THE COSMIC CORE-COLLAPSE SUPERNOVA RATE DOES NOT MATCH THE MASSIVE-STAR FORMATION RATE (2011, background): “The EBL has recently been constrained by the observations of gamma rays from distant blazars to be between these extremes (Aharonian et al. 2006; Albert et al. 2008; Abdo et al. 2010; Orr et al. 2011).”