Revisiting the Correlation between γ-Ray and Mid-Infrared Fluxes of the BL Lac Objects Detected by the FERMI Satellite

Out of the 395 BL Lacs in the Second FERMI AGN Catalog (2LAC) 337 have unique WISE counterparts located within 2.4" of the respective 2LAC directions. In the 3.4-4.6-12 μm color-color diagram, nearly all their colors lie in the WISE Blazar Strip (WBS), indicating that their Mid-infrared (MIR) emission is dominantly of non-thermal origin. Among these objects, the LBLs have on average larger MIR spectral-index values than the HBLs, and the IBLs seem to have such index values between LBLs and HBLs. Both the MIR spectral index and the γ-ray spectral index are strongly anti-correlated with the logarithm of the peak frequency of synchrortron radiation. There is a strong correlation between the γ-ray and MIR spectral indices. A strong correlation also exists between the 12μm and 1GeV fluxes.