C.D.S. - SIMBAD4 rel 1.7 - 2019.10.21CEST08:52:13

2007A&A...469..857D - Astronomy and Astrophysics, volume 469, 857-860 (2007/7-3)

Cascading on extragalactic background light.


Abstract (from CDS):

High-energy γ-ray propagating in the intergalactic medium can interact with background infrared photons to produce e+ e pairs, resulting in the absorption of the intrinsic γ-ray spectrum. TeV observations of the distant blazar 1ES 1101-232 were thus recently used to put an upper limit on the infrared extragalactic background light density. The created pairs can upscatter background photons to high energies, which in turn may pair produce, thereby initiating a cascade. The pairs diffuse on the extragalactic magnetic field (EMF) and cascade emission has been suggested as a means for measuring its intensity. Limits on the IR background and EMF are reconsidered taking into account cascade emissions. The cascade equations are solved numerically. Assuming a power-law intrinsic spectrum, the observed 100MeV-100TeV spectrum is found as a function of the intrinsic spectral index and the intensity of the EMF. Cascades emit mainly at or below 100GeV. The observed TeV spectrum appears softer than for pure absorption when cascade emission is taken into account. The upper limit on the IR photon background is found to be robust. Inversely, the intrinsic spectra needed to fit the TeV data are uncomfortably hard when cascade emission makes a significant contribution to the observed spectrum. An EMF intensity around 10–8nG leads to a characteristic spectral hump in the GLAST band. Higher EMF intensities divert the pairs away from the line-of-sight and the cascade contribution to the spectrum becomes negligible.

Abstract Copyright:

Journal keyword(s): radiation mechanisms: non-thermal - galaxies: BL Lacertae objects: individual: 1ES 1101-232 - galaxies: intergalactic medium - cosmology: diffuse radiation - gamma rays: observations

Simbad objects: 3

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Number of rows : 3

N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2019
1 2A 1058-226 BLL 11 03 37.6150843895 -23 29 31.202114088   17.00 16.55 16.61   ~ 302 2
2 Mrk 421 BLL 11 04 27.3139210166 +38 12 31.798324828   13.50 12.90 8.31   ~ 2330 1
3 NAME BL Lac BLL 22 02 43.2913773726 +42 16 39.978417860   15.66 14.72     ~ 1975 1

    Equat.    Gal    SGal    Ecl

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