Related papers: Limits on the extragalactic background light in th…
Extreme high-frequency peaked BL Lac objects (EHBLs) are blazars which exhibit extremely energetic synchrotron emission. They also feature non-thermal gamma-ray emission whose peak lies in the very high-energy (VHE, E > 100 GeV) range, and…
TeV photons from blazars at relatively large distances, interacting with the optical-IR cosmic background, are efficiently converted into electron-positron pairs. The produced pairs are extremely relativistic (Lorentz factors of the order…
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…
The very high energy (VHE) gamma-ray spectral indices of blazars show strong correlation with the source redshift. Absence of any such correlation in low energy gamma rays and X-rays indicate the presence of Extragalactic Background Light…
The Extragalactic Background Light (EBL) stands for the mean surface brightness of the sky as we would see it from a representative vantage point in the intergalactic space outside of our Milky Way Galaxy. Averaged over the whole 4 pi solid…
Decaying axion-like particles (ALP) with masses in the eV range which might occupy dark matter halos of the Milky Way and other galaxies produce a characteristic "bump" feature in the spectrum of extragalactic background light (EBL). This…
The Extragalactic Background Light (EBL) carries a huge astrophysical and cosmological content: its frequency spectrum and redshift evolution are determined by the integrated emission of unresolved sources, these being galaxies, active…
We present the redshift lower limit of z>0.6035 for the very-high-energy (VHE; E>100 GeV) emitting blazar PKS 1424+240 (PG 1424+240). This limit is inferred from Lyman beta and gamma absorption observed in the far-ultraviolet spectra from…
The Extragalactic Background Light (EBL) as an integrated light from outside of our Galaxy includes information of the early universe and the Dark Ages. We analyzed the spectral data of the astrophysical diffuse emission obtained with the…
Inverse-Compton cascades initiated by energetic gamma rays (E>100 GeV) enhance the GeV emission from bright, extragalactic TeV sources. The absence of this emission from bright TeV blazars has been used to constrain the intergalactic…
We explain the observed multiwavelength photon spectrum of a number of BL Lac objects detected at very high energy (VHE, $E \gtrsim 30$ GeV), using a lepto-hadronic emission model. The one-zone leptonic emission is employed to fit the…
The latest determination of the extragalactic gamma-ray background (EGRB) radiation by Fermi is compared with the theoretical prediction of the blazar component by Inoue & Totani (2009; hereafter IT09). The Fermi EGRB spectrum is in…
VHE (Very High Energy, E>100 GeV) radiation emitted at cosmological distances will pair produce on low-energy diffuse extragalactic background radiation before ever reaching us. This prevents us from directly seeing most of the VHE emission…
I review the constraints imposed by the observed extragalactic background light (EBL) on the history of the stellar birthrate in galaxies. At faint magnitudes, the logarithmic slope of the galaxy counts is flatter than 0.4 in all seven…
Observations of very-high-energy (VHE, E > 250 GeV) gamma-ray emission from several blazars at z > 0.1 have placed stringent constraints on the elusive spectrum and intensity of the intergalactic infrared background radiation (IIBR).…
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…
Properties of the extragalactic magnetic field (EGMF) outside of clusters and filaments of the large-scale structure are essentially unknown. The EGMF could be probed with $\gamma$-ray observations of distant (redshift $z > 0.1$) blazars.…
The energy spectra of TeV gamma-rays from blazars, after being corrected for intergalatic absorption in the Extragalactic Background Light (EBL), appear unusually hard, a fact that poses challenges to the conventional models of particle…
The observation in the GeV band of distant blazars has been recently used to put constraints on the Extragalactic Background Light (EBL) and Extragalactic Magnetic Fields (EGMF). To support such claims one has to assume that the leptonic…
Attenuation of the TeV gamma-ray flux from distant blazars through pair production with extragalactic background light leads to the development of electromagnetic cascades and subsequent, lower energy, GeV secondary gamma-ray emission. Due…