Constraints on the composition, magnetization, and radiative efficiency in jet of blazar

TL;DR

This study constrains the composition, magnetization, and radiative efficiency of blazar jets using low-frequency radio data, revealing high magnetization and efficiency, and suggesting magnetic reconnection as a key energy dissipation process.

Contribution

It provides new constraints on jet composition, magnetization, and radiative efficiency in blazars based on low-frequency radio observations, highlighting the role of magnetic reconnection.

Findings

Jet power from low-frequency radio is lower than from spectral energy distribution fitting.

Electron/positron pair fraction is constrained to about 10 times the proton number density.

Magnetization parameter is around 0.5, and radiative efficiency is about 0.4 in the dissipation region.

Abstract

The composition and energy dissipation in jets are two of the fundamental questions of jet physics that are not fully understood. In this paper, we attempt to constrain the composition, magnetization as well as radiative efficiency for blazar with the recently released low-frequency radio catalog of the TIFR GMRT Sky Survey at 150 MHz. The jet power estimated from the low-frequency radio emission is much lower than that derived from spectral energy distribution fitting assuming one proton per electron. Assuming the jet power estimated from low-frequency radio emission is physical, the fraction of electron/positron pairs can be constrained with $n_{\rm pairs}/n_{\rm p} \sim 10$. By comparing the power carried by magnetic field and radiation with the jet power estimated from the low-frequency radio emission, we find both relatively high magnetization parameter of $\sigma \sim 0.5$ and radiative efficiency of $\eta \sim 0.4$ in the dissipation region of blazars. These results suggest that the magnetic reconnection processes may play an important role in the energy dissipation of blazars. We also explore the connection between these three parameters ($n_{\rm pairs}/n_{\rm p}$, $\sigma$, and $\eta$) and the black hole mass, disk luminosity as well as Eddington ratio. No significant correlation is found, except that $\sigma$ shows possible correlation with disk luminosity.