Further evidence of superluminal active galactic nuclei as γ-ray sources

In our previous work in Xiao et al. (SCPMA, 2019, 62, 129811), we suggested that six superluminal sources could be γ-ray candidates, and in fact, five of them have been confirmed in the fourth Fermi-LAT source catalog (4FGL). In this work, based on the 4FGL, we report a sample of 229 Fermi detected superluminal sources (FDSs), including 40 new FDSs and 62 non-FDSs. Thus, we believe that all superluminal sources should have γ-ray emissions, and superluminal motion could also be a clue to detect γ-ray emission from active galactic nuclei. We present a new approach of Doppler factor estimate through the study of the γ-ray luminosity (Lγ) and of the viewing angle (ϕ).