Comparison between Fermi detected and non-Fermi detected superluminal sources

Active galactic nuclei (AGNs) have been attracting research attention due to their special observable properties. Specifically, a majority of AGNs are detected by Fermi-LAT missions, but not by Fermi-LAT, which raises the question of weather any differences exist between the two. To answer this issue, we compile a sample of 291 superluminal AGNs (189 FDSs and 102 non-FDSs) from available multi-wavelength radio, optical, and X-ray (or even γ-ray) data and Doppler factors and proper motion (μ) (or apparent velocity (βapp)); calculated the apparent velocity from their proper motion, Lorentz factor (Γ), viewing angle (ϕ) and co-moving viewing angle (ϕco) for the sources with available Doppler factor (δ); and performed some statistical analyses for both types. Our study indicated that (1) in terms of average values, FDSs have higher proper motions (μ), apparent velocities (βapp), Doppler factor (δ), Lorentz factor (Γ), and smaller viewing angle (ϕ). Nevertheless, there is no clear difference in co-moving viewing angles (ϕco). The results reveal that FDSs show stronger beaming effect than non-FDSs. (2) In terms of correlations: 1) both sources show positive, mutually correlated fluxes, which become closer in de-beamed fluxes; 2) with respect to apparent velocities and γ-ray luminosity, there is a tendency for the brighter sources to have higher velocities; 3) with regard to viewing angle and observed γ-ray luminosity, logϕ = −(0.23 ± 0.04)logLγ + (11.14 ± 1.93), while for the co-moving viewing angle and the intrinsic γ-ray luminosity, \(\rm{log}\phi_{co} = (0.09\pm0.01)\rm{log}\it{L}_\gamma^{\rm{in}}-\rm{(1.73\pm0.48)}\). These correlations show that the luminous γ-ray sources have smaller viewing angles and a larger co-moving viewing angle, which indicate a stronger beaming effect in γ-ray emissions.