Redshifts of distant blazar limited by Fermi and VHE $\gamma$-ray observations

Abstract

Our goal is to limit the redshifts of three blazars PG 1553+113, 3C 66A and PKS 1424+240, through the investigation of their Fermi and VHE (very high energy) $\gamma$-ray observations. We assume that the intrinsic spectra of PG 1553+113, 3C 66A, and PKS 1424+240 have not any cutoff across the Fermi and VHE $\gamma$-ray energy ranges. The intrinsic spectra of VHE $\gamma$-rays are obtained through the extrapolation of Fermi spectra. Comparing the measured and intrinsic VHE spectra due to extragalactic background light (EBL) absorption, we give the redshift upper limits of three blazars assuming a specific EBL model. The redshift upper limits of PG 1553+113, 3C 66A and PKS 1424+240 are 0.78, 0.58, and 1.19 respectively. Near the TeV energy the optical depth of VHE $\gamma$ photons might be overestimated by Franceschini (2008) EBL model, or the second emission component might be present in the VHE spectra and lead the intrinsic photon index harder than the Fermi ones.

arXiv comment4 pages, 2 figures, Accepted for publication in PASJ

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Cited by in corpus (14)

• Extragalactic Background Light Inferred from AEGIS Galaxy SED-type Fractions
• The Second Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope
• A model for periodic blazars
• Optical spectroscopic observations of gamma-ray blazars candidates I: preliminary results
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• Observations of the Blazar 3C 66A with the MAGIC Telescopes in Stereoscopic Mode
• Understanding the TeV emission from a distant blazar PKS 1424+240 in a lepto-hadronic jet model
• Redshift determination of the BL Lac object 3C66A by the detection of its host galaxy cluster at $z=0.340$
• A self-consistent interpretation of the GeV-TeV emission from a distant blazar PKS 1424+240
• Constraining the redshifts of TeV BL Lac objects
• Multi-epoch, multi-frequency VLBI study of the parsec-scale jet in the blazar 3C 66A
• Redshift measurement of the BL-Lac gamma-ray blazar PKS 1424+240
• Redshift constrain of BL Lac PKS 1424+240