Related papers: Intergalactic Extinction of High Energy Gamma-Rays
Recent experiments have measured the Galactic $\gamma$-ray diffuse emission up to PeV energies, opening a window to study acceleration of Galactic cosmic rays and their propagation up to the cosmic-ray knee. Furthermore, these observations…
We have undertaken a survey for HI 21-cm absorption within the host galaxies of z ~ 1.2 - 1.5 radio sources, in the search of the cool neutral gas currently "missing" at z > 1. This deficit is believed to be due to the optical selection of…
The X-ray source IGR J16318-4848 was the first source discovered by INTEGRAL on 2003, January 29. The high energy spectrum exhibits such a high column density that the source is undetectable in X-rays below 2 keV. On 2003, February, 23--25…
The recent HEGRA detection and spectrum of 1ES 1426+428 at TeV energies, once corrected for absorption using present estimates of the diffuse extragalactic IR background, suggest that the high energy peak of the Spectral Energy Distribution…
Markarian 421 was the first extragalactic source to be detected with high statistical certainty at TeV energies. The Whipple Observatory gamma-ray telescope has been used to observe the Active Galactic Nucleus, Markarian 421 in 1996 and…
We calculate the intensity and photon spectrum of the intergalactic background light (IBL) as a function of redshift using an approach based on observational data obtained in many different wavelength bands from local to deep galaxy…
Gamma-ray binaries are orbital modulated gamma-ray sources in the Galaxy detected both at GeV and TeV energies. The high-energy radiation may come from the interaction of energetic electrons injected by a young pulsar and photons from the…
I present the results of a new approach to the intensity and photon density spectrum of the intergalactic background light as a function of redshift using observational data obtained in many different wavelength bands from local to deep…
We extend our previous model-independent determination of the intergalactic background light (IBL), based purely on galaxy survey data, out to a wavelength of 5 microns. Our approach enables us to constrain the range of photon densities,…
We have developed the energy measurement method which based on stereoscopic observation with multiple telescopes for TeV gamma rays. Energy resolution obtained by this method was 23 %. The energy spectrum of the gamma-ray flares of…
We use high quality echelle spectra of 24 QSOs to provide a calibrated measurement of the total amount of Lyman-alpha forest absorption (DA) over the redshift range 2.2 < z < 3.2. Our measurement of DA excludes absorption from metal lines…
The interaction of TeV photons from blazars with the extragalactic background light produces a relativistic beam of electron-positron pairs streaming through the intergalactic medium (IGM). The fate of the beam energy is uncertain. By means…
We investigate the formation of TeV spectrum of a distant blazar PKS 1424+240 residing at a redshift $z\geq0.6$ in two scenarios in the frame of a lepto-hadronic jet model taking both the uncertainties of the extragalactic background light…
The energy spectrum of Mkn501 in the TeV energy regime, as measured by the HEGRA (High Energy Gamma Ray Astronomy) Cerenkov telescopes during its low state in 1995/96 and during a fraction of the 1997 outburst in the TeV energy regime, is…
We find a bright (L_{UV}=2.5 L*_{z=6}) Lyman alpha emitter at redshift z=5.719 at a projected distance of 79 physical kpc from a strong triply ionized carbon (Civ) absorption system at redshift z=5.7238 previously reported in the spectrum…
We update the list of GeV-TeV extragalactic \gamma-ray sources using the 2-year catalog from the Fermi-LAT and recent results ground-based \gamma-ray telescopes. Breaks in the spectra between the high energy (100 MeV <E< 300 GeV) and the…
We present a comprehensive analysis of the relationship between galaxies and the intergalactic medium (IGM) during the late stages of cosmic reionization, based on the complete JWST EIGER dataset. Using deep NIRCam $3.5\,\mathrm{\mu m}$…
Gamma rays have been observed from two blazars at TeV energies. One of these, Markarian 421, has been observed also at GeV energies and has roughly equal luminosity per decade at GeV and TeV energies. Photon-photon pair production on the…
A new method to constrain the distance of blazars with unknown redshift using combined observations in the GeV and TeV regimes will be presented. The underlying assumption is that the Very High Energy (VHE) spectrum corrected for the…
More than 90% of the Galactic gas-related gamma-ray emissivity above 1 GeV is attributed to the decay of neutral pions formed in collisions between cosmic rays and interstellar matter, with lepton-induced processes becoming increasingly…