The relationship between the radio core-dominance parameter and spectral index in different classes of extragalactic radio sources(Ⅱ)

Active galactic nuclei(AGNs) can be divided into two major classes, namely radio-loud and radio-quiet AGNs. A small subset of the radio-loud AGNs is called blazars, which are believed to be unified with Fanaroff-Riley type Ⅰ/Ⅱ(FRI/Ⅱ) radio galaxies. Following our previous work(Fan et al.), we present a sample of 2400 sources with measured radio flux densities of the core and extended components. The sample contains 250 BL Lacs, 520 quasars, 175 Seyferts, 1178 galaxies, 153 FRI or FRⅡ galaxies and 104 unidentified sources. We then calculate the radio core-dominance parameters and spectral indices, and study their relationship. Our analysis shows that the core-dominance parameters and spectral indices are quite different for different types of sources. We also confirm that the correlation between core-dominance parameter and spectral index exists for a large sample presented in this work.

The relationship between the radio core-dominance parameter and spectral index in different classes of extragalactic radio sources(Ⅲ)

Active galactic nuclei(AGNs) can be divided into two major classes,namely radio-loud and radio-quiet AGNs.A small subset of the radio-loud AGNs is called blazars,which are believed to be unified with Fanaroff-Riley type Ⅰ and type Ⅱ(FRI&Ⅱ) radio galaxies.Following our previous work,we present a latest sample of 966 sources with measured radio flux densities of the core and extended components.The sample includes 83 BL Lacs,473 flat spectrum radio quasars,101 Seyferts,245 galaxies,52 FRIs&Ⅱs and12 unidentified sources.We then calculate the radio core-dominance parameters and spectral indices and study their relationship.Our analysis shows that the core-dominance parameters and spectral indices are quite different for different types of sources.We also confirm that the correlation between core-dominance parameter and radio spectral index extends over all the sources in a large sample presented.

Correlation between Brightness Variability and Spectral Index Variability for Fermi Blazars

In this work,theγ-ray photon flux,photon spectral index(α_(ph)),variability index(log V.I.),and the synchrotron peak frequency(log v_(p))are compiled for 851 common blazars from the 3 FGL and 4 FGL catalogs and Fan et al.to investigate variability properties for Fermi blazars.Our calculations and analyses reach following results:(1)the averaged luminosity,spectral index,and variability index of FSRQs are higher than those of BL Lacs for the whole sample.(2)It is found that the spectral index variation is closely anti-correlated with the luminosity variation implying that the spectrum becomes harder when the source becomes brighter in theγ-ray band.(3)Positive correlations are found between the photon spectral index and bothγ-ray luminosity and variability index(log V.I.)for the whole sample,but anti-correlations are found in the two correlations for FSRQs.For BL Lac subclass,there is a marginal anti-correlation between the photon spectral index and bothγ-ray luminosity,and a positive correlation between the photon spectral index and the variability index(log V.I.).We think those two positive correlations found for the whole sample are apparent.(4)We adopted the SVM machine learning method to separate BL Lacs and FSRQs in theα_(ph)versus log L_(γ)andα_(ph)versus log V.I.plots and proposed that a BCU is an FSRQ candidate if it satisfies log V.I.>-10.119 a+24.855,orα_(ph)>-0.048 log L_(γ)+4.498,otherwise,it is a BL Lac candidate.Our classification results are quite consistent with those by Kang et al(2019).