In this paper, based on an archive sample of 542 extragalactic radio sources with available core dominance parameter, radio core luminosity and flux, redshift, we identified 80 radio sources with corresponding ?-ray emission, and investigated the correlations between core dominance parameter and multiple parameters.Through the comparison of 80 Fermi sources(22 BL Lacs, 44 quasars,14 galaxies) and 462 non-Fermi sources(5 BL Lacs, 171 quasars, 286galaxies), we found that: 1) the Fermi sources have larger mean R values and smaller redshifts. 2) the Fermi sources have on average higher core luminosity. These results suggest that the Fermi sources should be more compact, and beaming effect should play a crucial role for the detection of ?-ray emission. While we can not exclude the possibility that their intrinsic flux might also plays a role. Meanwhile, the Fermi sources have systematically larger radio flux than non-Fermi sources at fixed core dominance parameter and redshift, the results indicate the stong correlation between ?-ray emission and radio emission. Together with the result in Wu et al.(2014) which shows the Fermi BL Lacs have systematically larger radio flux than non-Fermi BL Lac at fixed Doppler factor. It fully illustrated the non-Fermi sources not only have the low intrinsic radio core flux than Fermi sources, but also have the low intrinsic ?-ray flux.This all indicate the closely correlation between radio and ?-ray emission. The results further indicate the radio and ?-ray emission might come from the same radiation area for our sample of AGNs. |