Related papers: Blazar halos as probe for extragalactic magnetic f…
Extremely high-peaked BL Lac objects (or extreme blazars) are unique extragalactic laboratories where particle acceleration processes are pushed at their physical limits. In these blazars, synchrotron emission peaking above keV energies is…
Context. Measurements of the Extragalactic Background Light (EBL) are a fundamental source of information on the collective emission of cosmic sources. Aims. At infrared wavelengths, however, these measurements are precluded by the…
The propagation of very-high-energy gamma-rays (VHEGRs) in the extragalactic space offers the opportunity to study astrophysical phenomena not reproducible in laboratories. In particular, the deviation from predictions of the observed…
The extragalactic background light (EBL) is the second-most-intense form of cosmic background light (the first being the cosmic microwave background) and contains the redshifted optical radiation, from infra-red to ultraviolet, emitted…
Blazars are a subclass of AGN and flaring in multi-TeV gamma-ray seems to be the major activity in high energy blazars a subgrup of blazars. Flaring is also unpredictable and switches between quiescent and active states involving different…
High energy observations of extreme BL Lac objects, such as 1ES 0229+200 or 1ES 0347-121, recently focused interest both for blazar and jet physics and for the implication on the extragalactic background light and intergalactic magnetic…
Blazars are a subclass of active galactic nuclei (AGN) that have a relativistic jet with a small viewing angle towards the observer. Recent results based on hadronic scenarios have motivated an ongoing discussion of how a blazar can produce…
Ultra high energy photons play an important role as an independent probe of the photo-pion production mechanism by UHE cosmic rays. Their observation, or non-observation, may constrain astrophysical scenarios for the origin of UHECRs and…
One of the most promising ways to probe intergalactic magnetic fields (IGMFs) is through gamma rays produced in electromagnetic cascades initiated by high-energy gamma rays or cosmic rays in the intergalactic space. Because the charged…
The light emitted by stars and accreting compact objects through the history of the Universe is encoded in the intensity of the extragalactic background light (EBL). Knowledge of the EBL is important to understand the nature of star…
The emission of very-high-energy photons (VHE, E$>$100 GeV) in active galactic nuclei (AGN) is closely connected with the production of ultra-relativistic particles. Among AGN, the subclass of extreme BL Lacertae are of particular interest…
Recent detections of very-high-energy (VHE, E > 100 GeV) gamma-ray blazars which do not belong to the high frequency peaked BL Lac (HBL) class, suggest that gamma-gamma absorption and pair cascading might occur in those objects. In the…
The extragalactic magnetic field (EGMF) could be probed with $\gamma$-ray observations of distant sources. Primary very high energy (VHE) $\gamma$-rays from these sources absorb on extragalactic background light photons, and secondary…
Ultra-high energy (UHE) photons play an important role as an independent probe of the photo-pion production mechanism by UHE cosmic rays. Their observation, or non-observation, may constrain astrophysical scenarios for the origin of UHECRs…
Very high energy photons from cosmological gamma-ray bursts (GRBs) are expected to interact with extragalactic background light (EBL) and produce electron-positron pairs when they propagate through intergalactic medium (IGM). These…
We present a new assessment of the contribution of Blazars to the extragalactic background radiation across the e.m. spectrum. Our calculations rely on deep Blazar radio counts that we derived combining several multifrequency surveys. The…
The Extragalactic Background Light (EBL) is the main radiation field responsible for attenuating extragalactic gamma-ray emission at very high energies, but its precise spectral intensity is not fully determined. Therefore, disentangling…
Blazars may accelerate protons and/or nuclei as well as electrons. The hadronic component of accelerated particles in blazars may constitute the bulk of their high-energy budget; nevertheless, this component is elusive due to a high value…
Discoveries of very high energy (VHE) photons from distant blazars suggest that, after correction by extragalactic background light (EBL) absorption, there is a flatness or even a turn-up in their spectra at the highest energies that cannot…
The extragalactic background light (EBL), a diffuse photon field in the optical and infrared range, is a record of radiative processes over the Universe's history. Spectral measurements of blazars at very high energies ($>$100 GeV) enable…