On the influence of a Hybrid Thermal-Non thermal distribution in the Internal Shocks model for blazars

Abstract

Internal shocks occurring in blazars may accelerate both thermal and non-thermal electrons. In this paper we examine the consequences that such a hybrid (thermal/non-thermal) EED has on the spectrum of blazars. Since the thermal component of the EED may extend to very low energies. We replace the standard synchrotron process by the more general magneto-bremsstrahlung (MBS). Significant differences in the energy flux appear at low radio frequencies when considering MBS instead of the standard synchrotron emission. A drop in the spectrum appears in the all the radio band and a prominent valley between the infrared and soft X-rays bands when a hybrid EED is considered, instead of a power-law EED. In the $γ$-ray band an EED of mostly thermal particles displays significant differences with respect to the one dominated by non-thermal particles. A thermally-dominated EED produces a synchrotron self-Compton (SSC) peak extending only up to a few MeV, and the valley separating the MBS and the SSC peaks is much deeper than if the EED is dominated by non-thermal particles. The combination of these effects modifies the Compton dominance of a blazar, suggesting that the vertical scatter in the distribution of FSRQs and BL Lac objects in the peak synchrotron frequency - Compton dominance parameter space could be attributed to different proportions of thermal/non-thermal particles in the EED of blazars. Finally, the temperature of the electrons in the shocked plasma is shown to be a degenerated quantity for different magentizations of the ejected material.