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 ( β app )); calculated the apparent velocity from their proper motion, Lorentz factor (Γ), viewing angle ( ϕ ) and co-moving viewing angle ( ϕ co ) 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 ( β app ), Doppler factor ( δ ), Lorentz factor (Γ), and smaller viewing angle ( ϕ ). Nevertheless, there is no clear difference in co-moving viewing angles ( ϕ co ). 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, log ϕ = −(0.23 ± 0.04)log L γ + (11.14 ± 1.93), while for the co-moving viewing angle and the intrinsic γ -ray luminosity, l o g ϕ c o = ( 0.09 ± 0.01 ) l o g L γ i n − ( 1.73 ± 0.48 ) . 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.