Related papers: Intergalactic Extinction of High Energy Gamma-Rays
We discuss the results of modelling the TeV gamma-ray spectra of two AGNs, Mkn 501 and Mkn 421 that have almost the same redshifts: z=0.031 and z=0.034, respectively. The effect of intergalactic gamma-ray absorption is treated as an…
The case of gamma-ray absorption due to photon-photon pair production of jet photons in the external photon environment like accretion disk and broad-line region radiation field of gamma-ray loud active galactic nuclei (AGN) that exhibit…
The question of a possible redshift-dependence of gamma-ray absorption due to gamma-gamma pair production of jet photons in the accretion disk and BLR radiation field in strong-line quasars is investigated. For this relevant aspects of…
This paper represents a step toward constraining galaxy formation models via TeV gamm a ray observations. We use semi-analytic models of galaxy formation to predict a spectral distribution for the intergalactic infrared photon field, which…
The detection of TeV gamma-rays from the blazar H 1426+428 at an integral flux level of (4 +- 2(stat) +- 1(syst)) 10^(-12) erg cm^(-2) s^(-1) above 1 TeV with the HEGRA imaging atmospheric Cherenkov telescope system is reported. H 1426+428…
The absorption of TeV $\gamma$-ray photons produced in relativistic jets by surrounding soft photon fields is a long-standing problem of jet physics. In some cases the most likely emission site close to the central black hole is ruled out…
We examine the effect of gamma-ray absorption by the extragalactic infrared radiation on intrinsic spectra predicted for 1ES0229+200 and compare our results with the observational data. We find agreement with our previous results on the…
We provide an in-depth analysis of the He II and H I absorption in the intergalactic medium (IGM) at redshifts z = 2.3-2.9 toward HE 2347-4342, using spectra from the Far Ultraviolet Spectroscopic Explorer (FUSE) and the Ultraviolet-Visual…
Blazars with redshifts z<0.1 are likely candidates for detection at energies in the range 300 GeV - 50 TeV with Cerenkov telescopes and scintillator arrays. We present gamma-ray flux predictions for a sample of 15 nearby flat-spectrum radio…
We discuss expectations for the absorption of high-energy gamma-rays by gamma-gamma pair production with intergalactic radiation fields (IRFs) at very high redshifts (z~5-20), and the prospects thereof for probing the cosmic reionization…
The determination of the densities of intergalactic photons from the FIR to the UV produced by stellar emission and dust reradiation at various redshifts can provide an independent measure of the star formation history of the universe. High…
Very high energy (VHE) gamma-rays have been detected from the direction of the Galactic center. The H.E.S.S. Cherenkov telescopes have located this gamma-ray source with a preliminary position uncertainty of 8.5" per axis (6" statistic + 6"…
Very high energy (VHE) gamma-ray emission from a distant source (z >~0.2) can be efficiently absorbed my means of the electron-positron pair creation process. Analyses of the unabsorbed spectra imply that the intrinsic TeV emission of some…
The International Gamma-Ray Astrophysics Laboratory (INTEGRAL) is discovering a large number of new hard X-ray sources, many of them being HMXBs. The identification and spectral characterization of their optical/infrared counterparts is a…
We have made radio- and millimeter-wavelength interferometric observations of a variety of molecular absorption lines toward the gravitational lens systems B0218+357 and PKS1830-211. The absorption occurs in the lensing galaxies at…
The spectra of very high energy gamma-radiation from distant extragalactic objects suffer significant deformations during the passage of primary gamma-rays through the intergalactic medium. The recently reported fluxes of diffuse infrared…
Several high-frequency peaked BL Lac objects such as Mrk 501 are strong TeV emitters. However, a significant fraction of the TeV gamma rays emitted are likely to be absorbed in interactions with the diffuse IR background, yielding…
Recent observations of the TeV gamma-ray spectra of the two closest active galactic nuclei (AGNs), Markarian 501 (Mrk 501) and Markarian 421 (Mrk 421), by the Whipple and HEGRA collaborations have stimulated efforts to estimate or limit the…
The next generation of gamma-ray telescopes may be able to observe gamma-ray blazars at high redshift, possibly out to the epoch of reionization. The spectrum of such sources should exhibit an absorption edge due to pair-production against…
I discuss how measurements of the absorption of $\gamma$-rays from GeV to TeV energies via pair production on the extragalactic background light (EBL) can probe important issues in galaxy formation. We use semi-analytic models (SAMs) of…