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Title: Estimation of the extragalactic background light using TeV observations of BL Lac objects

The very high-energy (VHE) gamma-ray spectral index of high-energy peaked blazars correlates strongly with its corresponding redshift, whereas no such correlation is observed in the X-ray or GeV bands. We attribute this correlation to photon-photon absorption of TeV photons with the extragalactic background light (EBL), and utilizing this we compute the allowed flux range for the EBL, which is independent of previous estimates. The observed VHE spectrum of the sources in our sample can be well approximated by a power law, and if the de-absorbed spectrum is also assumed to be a power law, then we show that the spectral shape of EBL will be εn(ε) ∼ klog (ε/ε {sub p}). We estimate the range of values for the parameters defining the EBL spectrum, k and ε {sub p}, such that the correlation of the intrinsic VHE spectrum with redshift is nullified. The estimated EBL depends only on the observed correlation and the assumption of a power-law source spectrum. Specifically, it does not depend on the spectral modeling or radiative mechanism of the sources or on any theoretical shape of the EBL spectrum obtained through cosmological calculations. The estimated EBL spectrum is consistent with the upper and lower limits imposedmore » by different observations. Moreover, it also agrees closely with the theoretical estimates obtained through cosmological evolution models.« less
Authors:
;  [1] ; ;  [2] ;  [3]
  1. Department of High Energy Physics, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India)
  2. Astrophysical Sciences Division, Bhabha Atomic Research Center, Mumbai (India)
  3. Inter-University Center for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune 411007 (India)
Publication Date:
OSTI Identifier:
22370276
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 795; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; APPROXIMATIONS; BACKGROUND RADIATION; BL LACERTAE OBJECTS; CORRELATIONS; GALAXIES; GAMMA RADIATION; GEV RANGE; PHOTONS; RED SHIFT; SPECTRA; TEV RANGE; VISIBLE RADIATION; X RADIATION