The Spectral Energy Distributions for 4FGL Blazars

Abstract

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.

Exploring TeV candidates of Fermi blazars through machine learning

“…While, Fan et al (2016) proposed slightly different criteria: 14 < log ν s p ≤ 15.3 for ISP, and log ν s p > 15.3 for HSP. Very recently, Yang et al (2022a) also gave a similar classification.…”

The “Blazar Sequence” in the TeV Band

“…There are 81 blazars, of which 67 are BL Lacs, nine are FSRQs, and five are blazar candidates of uncertain type (BCUs), confirmed as TeV emitters by associating TeVCat and 4FGL_DR3 (Abdollahi et al 2022). We collect the TeV spectrum information from the literature and the synchrotron peak frequency (log p ob n ) from Fan et al (2016) and Yang et al (2022a) for these sources. In this case, we compile a sample of 57 out of these 81 TeV blazars with available quiescent state or (and) flaring state TeV spectra.…”

“…The high-energy hump occurs at MeV to GeV energies, which is produced either by the inverse Compton process in a leptonic scenario (Tavecchio et al 1998;Ghisellini & Tavecchio 2009;Tan et al 2020) or proton synchrotron emission in a hadronic scenario (Mücke et al 2003;Böttcher et al 2009;Cerruti et al 2015;Cerruti et al 2019), or even a hybrid scenario (Gao et al 2019;Xue et al 2022). According to the synchrotron peak frequency, blazars can be divided into low-synchrotron-peaked sources (LSPs), intermediate-synchrotron-peaked sources (ISPs), and high-synchrotron-peaked sources (HSPs; Abdo et al 2010;Fan et al 2016;Yang et al 2022a).…”

Characterizing the Emission Region Properties of Blazars

“…The former are characterized by an optical spectrum with strong emission lines (rest-frame equivalent width, EW > 5 Å), while the latter demonstrate no or weak emission features (EW < 5 Å; Urry & Padovani 1995;Scarpa & Falomo 1997). Broadband studies illustrate a typical twohump spectral energy distribution (SED), the lower-energy bump ranging from radio to the X-ray band and peaking at the infrared to X-ray band, which is believed to be the synchrotron emission of the relativistic electrons in the jet, with the higherenergy bump ranging from the X-ray band to the γ-ray band and peaking at the X-ray to GeV γ-ray band (Abdo et al 2010;Fan et al 2016;Paliya et al 2021;Yang et al 2022Yang et al , 2023. The radiation mechanism of the higher-energy bump is still controversial; the leptonic model suggests that the higher-energy bump is attributed to the inverse Compton (IC) process (Blandford & Koenigl 1979;Sikora et al 1994;Sokolov & Marscher 2005;H.…”