Intrinsic VHE Gamma-ray spectra of Blazars as a probe for Extragalactic Background Light

Abstract

Very high energy (VHE) $\gamma$-rays above 10${}^{\prime }$s of GeV energy, emitted from distant blazars, are attenuated by photons from the extragalactic background light (EBL). Unfortunately, neither the EBL nor the intrinsic blazar spectrum is accurately known to derive one quantity from the other. In this work we use a homogeneous one zone model involving synchrotron, synchrotron self Compton (SSC) and external Compton (EC) emission mechanisms to estimate the intrinsic VHE spectra of blazars. The model is applied on three VHE blazars, namely PKS2155-304, RGB J0710+591 and 3C279, for which simultaneous multi-wavelength data are available from various observations. The predicted values of the intrinsic VHE fluxes are then compared with the observations by imaging atmospheric Cherenkov telescopes to determine the optical depth of VHE $\gamma$-rays. On comparing these optical depth values with those predicted by four different EBL models, we observe a somewhat pronounced systematic deviation for PKS2155-304 and 3C279 at higher energies, especially for the EBL model proposed by Finke et al.(2010). We attribute this deviation to be an outcome of either the failure of the extrapolation of blazar SED to VHE energies and/or due to various assumptions buried in the EBL models.

7 Figures

References in corpus (10)

• Very-High-Energy Gamma Rays from a Distant Quasar: How Transparent Is the Universe?
• The blazar sequence: a new perspective
• The Imprint of The Extragalactic Background Light in the Gamma-Ray Spectra of Blazars
• New limits on the density of the extragalactic background light in the optical to the far-infrared from the spectra of all known TeV blazars
• Measurement of the extragalactic background light imprint on the spectra of the brightest blazars observed with H.E.S.S
• Simultaneous observations of PKS 2155-304 with H.E.S.S., Fermi, RXTE and ATOM: spectral energy distributions and variability in a low state
• Formation of hard VHE gamma-ray spectra of blazars due to internal photon-photon absorption
• Hard TeV spectra of blazars and the constraints to the IR intergalactic background
• A Two Zone Synchrotron Model for the Knots in the M87 Jet
• Measuring the extragalactic background light from very high energy gamma-ray observations of blazars

Cited by in corpus (11)

• Long term multi-wavelength view of the blazar 1ES 1218+304
• Estimation of the Extragalactic Background Light using TeV Observations of BL~Lacs
• Extremely High energy peaked BL Lac nature of the TeV blazar Mrk 501
• Study of short term enhanced TeV $\gamma$- ray emission from Mrk 421 observed with TACTIC on December 28, 2014
• Extragalactic background light models and GeV-TeV observation of blazars
• Understanding the giant gamma-ray outburst on June 16, 2015 from the blazar 3C 279
• Probing the evolution of the EBL photon density out to $z\sim 1$ via $\gamma$-ray propagation measurements with Fermi
• Artificial Neural Networks for cosmic gamma-ray propagation in the Universe
• An Artificial Intelligence based approach for constraining the redshift of blazars using $\gamma$--ray observation
• Central Engine and Spectral Energy Distribution Properties of High Redshift Gamma Ray Blazars
• Intrinsic GeV-TeV gamma-ray emission from EHSP blazars