By cross-correlating an archive sample of 542 extragalactic radio sources with the Fermi-LAT Third Source Catalog(3FGL), we have compiled a sample of 80 γ-ray sources and 462 non-Fermi sources with available core dominance parameter(RCD), and core and extended radio luminosity; all the parameters are directly measured or derived from available data in the literature. We found that RCD has significant correlations with radio core luminosity, γ-ray luminosity and γ-ray flux; the Fermi sources have on average higher RCD than non-Fermi sources. These results indicate that the Fermi sources should be more compact,and the beaming effect should play a crucial role in the detection of γ-ray emission. Moreover, our results also show Fermi sources have systematically larger radio flux than non-Fermi sources at fixed RCD, indicating larger intrinsic radio flux in Fermi sources. These results show a strong connection between radio andγ-ray flux for the present sample and indicate that the non-Fermi sources are likely due to the low beaming effect, and/or the low intrinsic γ-ray flux. This supports a scenario that has been published in the literature:a co-spatial origin of the activity for the radio and γ-ray emission, suggesting that the origin of the seed photons for the high-energy γ-ray emission is within the jet.
Stars are born in dense cores of molecular clouds. The core mass function(CMF), which is the mass distribution of dense cores, is important for understanding the stellar initial mass function(IMF). We obtained 350 μm dust continuum data using the SHARC-II camera at the Caltech Submillimeter Observatory(CSO) telescope. A 350 μm map covering 0.25 deg2 of the Ophiuchus molecular cloud was created by mosaicing 56 separate scans. The CSO telescope had an angular resolution of 9′′, corresponding to 1.2×103AU at the distance of the Ophiuchus molecular cloud(131 pc). The data was reduced using the Comprehensive Reduction Utility for SHARC-II(CRUSH). The flux density map was analyzed using the Gauss Clumps algorithm, within which 75 cores has been identified. We used the Spitzer c2 d catalogs to separate the cores into 63 starless cores and 12 protostellar cores. By locating Jeans instabilities, 55 prestellar cores(a subcategory of starless cores) were also identified. The excitation temperatures, which were derived from FCRAO12 CO data, help to improve the accuracy of the masses of the cores. We adopted a Monte Carlo approach to analyze the CMF with two types of functional forms; power law and log-normal. The whole and prestellar CMF are both well fitted by a log-normal distribution, with μ =-1.18±0.10, σ = 0.58±0.05 and μ = 1.40±0.10, σ = 0.50±0.05 respectively. This finding suggests that turbulence influences the evolution of the Ophiuchus molecular cloud.
