New limits on the density of the extragalactic background light in the optical to the far-infrared from the spectra of all known TeV blazars

By D. Mazin, Martina Raue. 2007

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Aims. The extragalactic background light (EBL) in the ultraviolet to far-infrared wavelength region carries important information about galaxy and star formation history. Direct measurements are difficult, especially in the mid infrared region. We derive limits on the EBL density from the energy spectra of distant sources of very high energetic γ-rays (VHE γ-rays). Methods. The VHE γ-rays are attenuated by the photons of the EBL via pair production, which leaves an imprint on the measured spectra from distant sources. So far, there are 14 detected extragalactic sources of VHE γ-rays, 13 of which are TeV blazars. With physical assumptions about the intrinsic spectra of these sources, limits on the EBL can be derived. In this paper we present a new method of deriving constraints on the EBL. Here, we use only very basic assumptions about TeV blazar physics and no pre-defined EBL model, but instead a large number of generic shapes constructed from a grid in EBL density vs. wavelength. In our study we utilize spectral data from all known TeV blazars, making this the most complete study so far. Results. We derive limits on the EBL for three individual TeV blazar spectra (Mkn 501, H 1426+428, 1ES 1101-232) and for all spectra combined. Combining the results from individual spectra leads to significantly stronger constraints over a wide wavelength range from the optical (∼1 µm) to the far-infrared (∼80 µm). The limits are only a factor of 2 to 3 above the absolute lower limits derived from source counts. In the mid-infrared our limits are the strongest constraints derived from TeV blazar spectra so far over an extended wavelength range. A high density of the EBL around 1 µm, reported by direct detection experiments, can be excluded. Conclusions. Our results can be interpreted in two ways. (i) The EBL is almost resolved by source counts, leaving only a little room for additional components, such as the first stars, or (ii) the assumptions about the underlying physics are not valid, which would require substantial changes in the standard emission models of TeV blazars.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/70ee5cecb9eaef793e1366ab4b6ddad88011466a

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Citations in the corpus

The extragalactic background light and the gamma-ray opacity of the universe (2012, background): “A comprehensive study by Mazin & Raue (2007) is based on eleven blazars over a redshift range from 0.03 - 0.18, and explores a large number (8 million) of hypothetical EBL scenarios to set upper limits on the EBL, again with the requirement that the source spectra cannot be harder than Γ = 1.5 or Γ…”
Measurement of the extragalactic background light imprint on the spectra of the brightest blazars observed with H.E.S.S. (2012, background): “Assuming that there is no intrinsic break in the energy range of interest (as in Stecker et al. 1992) and that the hardness of the spectrum is limited, stringent upper limits on the EBL opacity to γ-rays have been derived (e.g. Aharonian et al. 2006c; Mazin & Raue 2007).”
CONTRIBUTION OF GAMMA-RAY-LOUD RADIO GALAXIES’ CORE EMISSIONS TO THE COSMIC MeV AND GeV GAMMA-RAY BACKGROUND RADIATION (2011, background): “…(EBL), also called the cosmic optical and infrared background (Salamon & Stecker 1998; Totani & Takeuchi 2002; Kneiske et al. 2004; Stecker et al. 2006; Mazin & Raue 2007; Raue & Mazin 2008; Franceschini et al. 2008; Razzaque et al. 2009; Gilmore et al. 2009; Finke et al. 2010; Kneiske & Dole…”
Indications for a pair-production anomaly from the propagation of VHE gamma-rays (2012, background): “These analyses constrain the maximum level of the EBL consistently to be close to [18–20] and even slightly below (in the mid-infrared) [21] the guaranteed level of the EBL [22].”
MAGIC DISCOVERY OF VERY HIGH ENERGY EMISSION FROM THE FSRQ PKS 1222+21 (2011, methodology): “EBL limits The interaction of very high energy γ-rays with low energy photons of the isotropic EBL is a process with an energy dependent threshold, thus leading to an imprint of the EBL density on the measured VHE γ-ray spectra of extragalactic sources (Mazin & Raue 2007).”
Extragalactic optical-infrared background radiation, its time evolution and the cosmic photon-photon opacity (2008, background): “…of absorption featur s in the high-energy spectra of distant BLAZARs may be used to place relevant constraints on the spectral intensity of background radiation (see also Stecker and De Jager 1993, Dwek and Slavin 1994, Stanev and Franceschini 1998, Renault et al. 2001, Mazin and Raue 2007).”
Teraelectronvolt Astronomy (2010, background): “Mazin & Raue (2007) have developed an approach where arbitrary EBL shapes are tested and constrained, confirming earlier EBL limits (Figure 16).”
ROLE OF LINE-OF-SIGHT COSMIC-RAY INTERACTIONS IN FORMING THE SPECTRA OF DISTANT BLAZARS IN TeV GAMMA RAYS AND HIGH-ENERGY NEUTRINOS (2010, methodology): “This can be explained by the lower levels of EBL (Aharonian et al. 2006b; Mazin & Raue 2007; Finke & Razzaque 2009), combined with much harder intrinsic spectra of distant blazars (Stecker et al. 2007) than those predicted by earlier models (Peacock 1981; Kirk & Schneider 1987; Heavens & Drury…”
Semi-analytic modelling of the extragalactic background light and consequences for extragalactic gamma-ray spectra: Modelling of the EBL and gamma-ray spectra (2012, methodology): “Other limits shown are the realistic limits of Mazin & Raue (2007) (purple), and the analysis of Dwek & Krennrich (2005) (orange triangle at 60 µm).”
Building the cosmic infrared background brick by brick with Herschel/PEP. ⋆ (2011, background): “This information is not only important to constrain models of galaxy evolution, butalso to shed light on the intrinsic spectra of TeV sources, such as BLAZARs, whoseγ-ray photons interact with the CIB (e.g. Domı́nguez et al. 2011; Franceschini et al. 2008; Mazin & Raue 2007).”
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).”
Cosmological Magnetic Fields: Their Generation, Evolution and Observation (2013, background): “…had then permitted to derive upper limits on the EBL density, rather than the full measurement of the EBL spectrum (Biller et al 1995; Funk et al 1998; Aharonian et al 2006, 2007a,b; MAGIC Collaboration et al 2008; Mazin and Raue 2007; Finke and Razzaque 2009; H.E.S.S. Collaboration et al 2012b) .”