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

TL;DR

This study models the spectral energy distribution of PKS 0447-439 using different electron energy distributions to understand the acceleration processes and estimate its redshift, finding stochastic acceleration likely in the jet.

Contribution

It compares multiple electron energy distribution models using MCMC to determine the most plausible acceleration process and estimates the redshift of PKS 0447-439.

Findings

Log-parabolic and broken power law models fit observed data well.

Shock-acceleration model fails to fit the observed SED.

Redshift estimated around 0.16 to 0.17.

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 (shock-acceleration 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 $z=0.16\pm0.05$ for LP case and $z=0.17\pm0.04$ for BPL case.