Unification of BL Lac objects and FR I and FR II(G) radio galaxies, and Doppler factor estimation for BL Lac objects

Abstract

Abstract In this work, we collected a sample of BL Lacs and FR I and FR II(G) radio galaxies with available core and extended emissions from published works to discuss the unified schemes and estimate the Doppler factor for BL Lacs. A Wilcoxon rank-sum test and a Kolmogorov–Smirnov test both suggest that the probabilities of the distribution of the extended luminosity of BL Lacs and that of FR I and FR II(G) radio galaxies being from the same parent distribution are pWRS = 0.779 and pK-S = 0.326, suggesting they are unified. Based on this unified scheme, we propose to estimate the Doppler factors for BL Lacs. Comparing the Doppler factor estimated by the fitting/regression method with those for the common sources in the literature, we found a good linear correlation for common sources.