The Ratio of the Core to the Extended Emissions in the Comoving Frame for Blazars

Abstract

In a two-component jet model, the emissions are the sum of the core and extended emissions: $S^{\mathrm{ob}}=S_{\mathrm{core}}^{\mathrm{ob}}+S_{\mathrm{ext}}^{\mathrm{ob}}$, with the core emissions, $S_{\mathrm{core}}^{\mathrm{ob}}=f{S}_{\mathrm{ext}}^{\mathrm{ob}}{\delta }^q$, being a function of the Doppler factor, $\delta$, the extended emission, $S_{\mathrm{ext}}^{\mathrm{ob}}$, jet type dependent factor, $q$, and the ratio of the core to the extended emissions in the comoving frame, $f$. The $f$ is an unobservable but important parameter. Following our previous work, we collect 65 blazars with available Doppler factor, $\delta$, superluminal velocity, ${\beta }_{app}$, and core-dominance parameter, $R$, calculate the ratio, $f$, and peform statistical analyses. We find that the ratio, $f$, in BL Lacs is on average larger than that in FSRQs. We suggest that the difference of the ratio $f$ between FSRQs and BL Lacs is one of the possible reasons that cause the difference of other observed properties between them. We also find some significant correlations between $\log f$ and other parameters, including intrinsic (de-beamed) peak frequency, $\log {\nu }_{\mathrm{p}}^{\mathrm{in}}$, intrinsic polarization, $\log P^{\mathrm{in}}$, and core-dominance parameter, $\log R$, for the whole sample. In addition, we show that the ratio, $f$, can be estimated by $R$.

arXiv commentAccepted by Journal of Astrophysics and Astronomy

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• Radio Core-Dominance of Fermi-Blazars: Implication for Blazar Unification