Measurement of the extragalactic background light using MAGIC and Fermi-LAT gamma-ray observations of blazars up to z = 1

Abstract

We present a measurement of the extragalactic background light (EBL) based on a joint likelihood analysis of 32 gamma-ray spectra for 12 blazars in the redshift range z = 0.03 − 0.944, obtained by the MAGIC telescopes and Fermi-LAT. The EBL is the part of the diffuse extragalactic radiation spanning the ultraviolet, visible and infrared bands. Major contributors to the EBL are the light emitted by stars through the history of the universe, and the fraction of it which was absorbed by dust in galaxies and re-emitted at longer wavelengths. The EBL can be studied indirectly through its effect on very-high energy photons that are emitted by cosmic sources and absorbed via γγ interactions during their propagation across cosmological distances. We obtain estimates of the EBL density in good agreement with state-of-the-art models of the EBL production and evolution. The 1σ upper bounds, including systematic uncertainties, are between 13% and 23% above the nominal EBL density in the models. No anomaly in the expected transparency of the universe to gamma rays is observed in any range of optical depth. We also perform a wavelength-resolved EBL determination, which results in a hint of an excess of EBL in the 0.18 -0.62 µm range relative to the studied models, yet compatible with them within systematics.

Progress in unveiling extreme particle acceleration in persistent astrophysical jets

“…Their hard spectra provided the first strong constraints to the maximum intensity of the EBL. Current TeV measurements rely on observations of both steady and temporary extreme-TeV blazars to constrain the longest wavelengths [65,66].…”

Non-thermal emission in lobes of radio galaxies – III. 3C 98, Pictor A, DA 240, Cygnus A, 3C 326, and 3C 236

“…We predict the Compton/(EBL+GFL) emission in the lobes using a recent EBL model (Franceschini & Rodighiero 2017;Acciari et al 2019) and by accounting for the host galaxy contribution (GFL) to the superposed radiation fields in the lobes. Very low Compton fluxes in the Fermi/LAT band are predicted from sources whose radio spectra imply EEDs with low γmax.…”

“…The CMB is a pure Planckian with TCMB = 2.725 K and energy density uCMB = 0.25 (1 + z) 4 eV cm −3 (e.g., Dermer & Menon 2009). The EBL, originating from direct and dust-reprocessed starlight integrated over the star formation history of the universe (e.g., Franceschini & Rodighiero 2017;Acciari et al 2019), can be represented as a suitable combination of diluted Planckians (see Paper II).…”

Ultrahigh-energy Cosmic-Ray Interactions as the Origin of Very High-energy γ-Rays from BL Lacertae Objects

“…The far-reaching progress made in γ−ray observations in the last decade and the considerable amount of data collected by Fermi-LAT (Fermi-LAT Collaboration et al 2015;Ackermann et al 2015), MAGIC (Acciari et al 2019), HESS (Aharonian et al 2006), VERITAS (VERITAS Collaboration et al 2018), HAWC (Abeysekara et al 2017a,b) experiments, etc., have evolved the understanding of our universe in the highenergy regime. The precision measurement of photon fluxes from a wide variety of astrophysical objects provides an impetus to study the γ−ray sky as a probe to various hadronic interaction processes.…”