Redshift determination of the BL Lac object 3C66A by the detection of its host galaxy cluster at $z=0.340$

Juanita Torres-Zafra, Sergio A. Cellone, Alberto Buzzoni +2

The BL Lac object 3C66A is one of the most luminous extragalactic sources at TeV $\gamma$-rays (VHE, i.e. $E>100$ GeV). Since TeV $\gamma$-ray radiation is absorbed by the extragalactic bac…