The physical properties of $Fermi$-4LAC flat spectrum radio quasars

TL;DR

This study models the spectral energy distributions of 60 Fermi-4LAC flat spectrum radio quasars to understand their jet physics, revealing correlations between electron acceleration, dissipation regions, and jet power, consistent with the blazar sequence.

Contribution

It provides a comprehensive analysis of FSRQ jet properties using quasi-simultaneous multi-wavelength data within the one-zone leptonic model, highlighting new correlations and jet region locations.

Findings

Linear correlation between synchrotron peak frequency and electron energy distribution curvature.

Gamma-ray dissipation regions are located 0.1 to 10 pc from the black hole, outside the BLR.

Jet power components suggest near equipartition and dominant EC radiation in FSRQs.

Abstract

In this work, we collect quasi-simultaneous infrared, optical, X-ray and $\gamma$-ray data of 60 $Fermi$-4LAC flat spectrum radio quasars (FSRQs). In the framework of the conventional one-zone leptonic model, we investigate the physical properties of $Fermi$-4LAC FSRQs' jets by modeling their quasi-simultaneous spectral energy distributions (SEDs). Our main results are summarized as follows. (1) There is a linear correlation between synchrotron peak frequency and curvature of the electron energy distribution. As suggested by previous works, the slope of the best linear fitting equation of this correlation is consistent with statistic acceleration which needs a fluctuation of fractional acceleration gain. (2) The gamma-ray dissipation regions are located at the range from 0.1 to 10 pc away from the super-massive black hole, and located outside the broad-line region (BLR) and within the dusty torus (DT). (3) A size relation $P_{\rm e}$ (the kinetic power carried in relativistic electrons) $\sim$ $P_{\rm B}$ (Poynting flux) $\leq$ $P_{\rm r}$ (the radiative power ) $<$ $P_{\rm p}$ (the kinetic power in cold protons) is found in our modeling. Among them, $P_{\rm e}\sim P_{\rm B}$ suggests that SEDs of almost all FSRQs with parameters are close to equipartition between the magnetic field and the relativistic electrons. The $P_{\rm e} < P_{\rm r}$ suggest that the most energy of the relativistic electrons are dissipated by EC radiation for FSRQs. (4) There is an anti-correlation between the peak energy of SEDs ($\gamma_{\rm peak}$) and the jet power ($P_{\rm jet}$), which is consistent with the blazar sequence.