Radio Core Dominance Of Fermi Sources

Active Galactic Nuclei?abbreviation: AGNs?are very interesting and attractive objects for researching in extragalactic sources,which have two major classes,namely radio loud AGNs and radio quiet AGNs.A small subset of the radio-loud AGNs is called Blazars,which display extreme observational properties,such as showing ?-ray radiation,rapid variability,high luminosity,high and variable polarization,and superluminal motion.All of those observational properties are probably due to a relativistic beaming effect with the jet pointing close to the line of sight.Blazars also have two subclasses,namely BL Lac and FSRQ.Observations suggest that the orientation can be expressed by a core-dominance parameter R,which defined as R =S_core/S_ext.,where S_coreand S_ext.stands for the emission in the core component and extended component,respectively.The R,to some extent,is associated with the beaming effect.After the launch of Fermi Large Area Telescope?Fermi LAT?,many sources have been detected to show high energetic ?-ray emission.In the latest catalogue?3FGL?,1444 sources are added by the former ones,and now are up to over 3000 sources,in which around 60% are AGNs,and 98% are Fermi Blazars.Variability index also plays an important role in discussing the mechanism of high energy emission.Those data has give us a good opportunity to study the high energy astrophysics and beaming effect.In this paper,we collected relevant observations from the literature for a sample of 2013 active galactic nuclei?AGNs?,which including 240 Fermidetected sources and 1173 non-Fermi-detected sources.Besides,the Fermi sources are included 89 Fermi BL Lacs,131 Fermi Quasars and 20 Fermi other sources,and while,the non-Fermi sources are included 56 non-Fermi BL Lacs,534 non-Fermi Quasars,676 non-Fermi radio Galaxies,206 noon-Fermi Seyfert Galaxies,181 non-Fermi Fanaroff-Riley Galaxies and 120 non-Fermi unidentified sources.We calculated the core-dominance parameters?log R?and radio spectral indexes??radio?,discussed the relationship between the two parameters,and gave some discussions.We found that the mean value of core dominance parameter for Fermi sources is higher than the case for non-Fermi sources,however,in contrary,the mean value of radio spectral index for Fermi sources is lower than the case for non-Fermi sources.A sequence is shown that: BL Lac > Quasar > Seyfert > Galaxy > FR type Galaxy.For radio spectral index,BL Lacs is higher than Quasars respect to Fermi sources.But for non-Fermi sources,the case is opposite comparing to log R.For both ?-ray spectral index and variability index,Quasar is higher than BL Lac.Meanwhile,We found that the core-dominance parameter ?radio and ? spectral index correlation exists for a large sample presented in this paper,which may come from a relativistic beaming effect.