Emitting Electron Spectra and Acceleration Processes in the Jet of PKS 0447-439

Abstract

We investigate the electron energy distributions (EEDs) and the corresponding acceleration processes in the jet of PKS 0447−439 and estimate its redshift through modeling its observed spectral energy distribution (SED) in the frame of a one-zone synchrotron-self Compton (SSC) model. Three EEDs formed in different acceleration scenarios are assumed: the power-law with exponential cut-off (PLC) EED (shockacceleration scenario or the case of the EED approaching equilibrium in the stochastic-acceleration scenario), the log-parabolic (LP) EED (stochastic-acceleration scenario and the acceleration dominating) and the broken power law (BPL) EED (no acceleration scenario), and then the corresponding fluxes of both synchrotron and SSC are calculated. The model is applied to PKS 0447-439 and modeling SEDs are compared to the observed SED of this object by using the Markov Chain Monte Carlo (MCMC) method. Calculating results show that PLC model fails to fit the observed SED well, while the LP and BPL models give comparably good fits for the observed SED. The results indicate that it is possible that stochastic acceleration process acts in the emitting region of PKS 0447-439 and the EED is far from equilibrium (acceleration dominating) or no acceleration process works (in the emitting region). The redshift of PKS 0447-439 is also estimated in our fitting, and z = 0.16 ± 0.05 for LP case and z = 0.17 ± 0.04 for BPL case.

RELATIVISTIC JET PROPERTIES OF GeV-TeV BLAZARS AND POSSIBLE IMPLICATIONS FOR THE JET FORMATION, COMPOSITION, AND CAVITY KINEMATICS

“…We also compare the parameter distributions of the electron spectra and the two peak frequencies of SEDs between the FSRQs and BL Lacs in Figures 9(b), (c), (d), (e). The distributions of p 2 for the two kinds of blazars 4 are consistent with the same mean of p 2 = 3.8. p 1 for BL Lacs is around 2, roughly consistent with the prediction of Fermi acceleration mechanism (Gallant 2002;Wang 2002;Cao & Wang 2013b;Zhou et al 2013). The distribution of p 1 for FSRQs is bimodal; half are consistent with that for BL Lacs and half have p 1 ∼ 1.2, implying the different acceleration process (Yan et al 2013).…”