Tramacere, Andrea

A panchromatic view of blazars: constraining acceleration and emission processes in relativistic jets using broadband SED fitting.

Author list: Andrea Tramacere

We investigate the phenomenological link between the shape of the blazars broadband spectral energy distribution (SED), ranging from the radio up to gamma-ray energies, and the underlying emitting electron distribution. We describe the methodology to use this connection to constrain the emission and acceleration processes acting in relativistic jets. In the first step we use a log-log polynomial fit of the observed SEDs to constrain the parameter space of the synchrotron self-Compton (SSC) and external Compton (EC) leptonic scenario. This allows us to mitigate some of the degeneracies among the model parameters, such as that between the beaming factor and the magnetic field intensity. The analysis of the SED shape allows us also to constrain the shape of the electron distribution. In the second step, the phenomenologically constrained parameters are used as input values for an accurate numerical code reproducing radiative and acceleration processes. The final best-fit parameters, with their confidence intervals and the goodness-of-fit estimation, are obtained by plugging the numerical code to different minimization algorithms and performing a model fit to the observed data. The whole process has been translated into a fitting/modeling code, that will be publicly distributed. In the present analysis we focus on the case of HBLs objects, investigating the shape of the electron distributions, comparing the best-fit models to self-consistent time-dependent analysis performed in the framework of the stochastic acceleration scenario, finding interesting constraints on the magnetic field intensity, and on the characterization of the flaring vs. equilibrium state.