In this paper, the multiwavelength data from radio to X-ray bands for 2709 blazars in the 4FGL-DR3 catalog are compiled to calculate their spectral energy distributions using a parabolic equation log ( ν f ν ) = P 1 log ν − P 2 2 + P 3 . Some important parameters including spectral curvature (P 1), synchrotron peak frequency (P 2, log ν p ), and peak luminosity ( log L p ) are obtained. Based on those parameters, we discussed the classification of blazars using the “Bayesian classification” and investigated some mutual correlations. We came to the following results. (1) Based on the Bayesian classification of synchrotron peak frequencies, the 2709 blazars can be classified into three subclasses, i.e., log ( ν p / Hz ) < 13.7 for low synchrotron peak blazars (LSPs), 13.7 < log ( ν p / Hz ) < 14.9 for intermediate synchrotron peak blazars (ISPs), and log ( ν p / Hz ) > 14.9 for high synchrotron peak blazars (HSPs), and there are 820 HSPs, 750 ISPs, and 1139 LSPs. (2) The γ-ray emission has the closest relationship with radio emission, followed by optical emission, while the weakest relationship is that with X-ray emission. The γ-ray luminosity is also correlated with the synchrotron peak luminosity. (3) There are strong positive correlations between the curvature (1/∣P 1∣) and the peak frequency ( log ν p ) for all subclasses (FSRQs, (high, intermediate, and low) BL Lacertae objects). For different subclasses, the correlation slopes are different, which implies that there are different acceleration mechanisms and emission processes for different subclasses of blazars.

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Based on a sample of radio galaxies, the effective spectrum index α RO (178 MHz to 0.54 μm), the radio and the V-band optical luminosities are investigated for FR-I, FR-II(G) and FR-II(Q).Key words. Radio galaxies-FR-I, FR-II(Q) and FR-II(G)-radio and V-band luminosities-luminosity distributions-unified model. Sample and calculations methodA sample including 137 radio galaxies (27 FR-I, 83 FR-II(G)s and 27 FR-II(Q)s) was collected from the available literature. The sample can be received by emails from the authors.We converted the V-magnitude into flux density using the formulae, f = f 0 × 10 −0.4m V , and f 0 = 3.64 kJy for V-band (Mead et al. 1990). The flux density is K-corrected using f K = f (1+z) (α−1) . The f K can be used to calculate the luminosity and effective spectrum index (α RO ).The luminosity can be calculated using ν L ν = 4πd 2 L ν f ν , here luminosity distance 2007), with H 0 = 73.00 km · s −1 · Mpc −1 , M = 0.27. ν is the frequency at radio and V-band respectively, ν V = 5.45 × 10 14 Hz (Mead et al. 1990), and ν R = 178 MHz.The effective spectrum index values, ResultsThe average values of the K-correcting radio and optical luminosities are as follows:For FR-I, log ν L 178 MHz R = 40.92±1.05 erg s −1 , log ν L 0.54 μm V = 43.92±0.36 erg s −1 . For FR-II(G), log ν L 178 MHz R = 42.95 ± 0.87 erg s −1 , log ν L 0.54 μm V = 44.19 ± 0.38 erg s −1 . For FR-II(Q), log ν L 178 MHz R = 43.99 ± 0.47 erg s −1 , log ν L 0.54 μm V = 45.74 ± 0.40 erg s −1 . 307