The Origin of Matter at the Base of Relativistic Jets in Active Galactic Nuclei

Abstract

The generation of relativistic jets in active sources such as blazars is a complex problem with many aspects, most of them still not fully understood. Relativistic jets are likely produced by the accretion of matter and magnetic fields onto spinning black holes. Ergospheric dragging effects launch a Poynting-dominated outflow in the polar directions of these systems. Observations with very high resolution of the jet in the nearby radio galaxy M87 and evidence of extremely fast variability in the non-thermal radiation of several other objects indicate that charged particles produce synchrotron emission and gamma rays very close to the base of the jet. How these particles are injected into the magnetically shielded outflow is a mystery. Here we explore the effects of various processes in the hot accretion inflow close to the black hole that might result in the copious production of neutral particles which, through annihilation and decay in the jet’s funnel, might load the outflow with mass and charged particles on scales of a few Schwarzschild radii.

The content of astrophysical jets

“… Left panel : Number of pairs created per unit time and volume by photon annihilation in a hot accretion flow as a function of the radius (distance to the black hole) in units of the Schwarzschild radius. Parameters similar to those of M87 (from Romero & Gutiérrez 2020). Right panel : Spectral energy distribution of the same electron/positron pairs in the innermost region of the accretion flow…”

“…This can only occur in the very central region of the sources. The basic features of the magnetic model for the generation of relativistic jets are the following (Koide et al 2000(Koide et al , 2002Meier et al 2001;Romero & Gutiérrez 2020;Tchekhovskoy 2015):…”

“…This can only occur in the very central region of the sources. The basic features of the magnetic model for the generation of relativistic jets are the following (Koide et al 2000, 2002; Meier et al 2001; Romero & Gutiérrez 2020; Tchekhovskoy 2015): Relativistic jets are produced by rapidly rotating BHs fed by magnetized accretion disks. The magnetic field geometry in the innermost region is dominated by the poloidal component. The ultimate power source is the rotational energy of the black hole. The energy is extracted via magnetic torque as Poynting flux. Jet collimation is due to the external medium outside the MAD zone 3 Jet acceleration is via conversion of the electromagnetic energy into bulk kinetic energy. …”

“…A possible answer is that charged particles are locally created by gamma‐ray photon annihilation and neutron decays. These neutral particles must be produced in the surrounding disk (Kimura et al 2014; Romero & Gutiérrez 2020; Toma & Takahara 2012; Vila et al 2014).…”

“…This flow can be loaded through neutral particles coming from the surrounding hot flow. More specifically, the particles and involved processes are as follows (Romero & Gutiérrez 2020): High‐energy photons . They are generated in the hot flow by several processes (most notably proton‐synchrotron and proton‐photon interactions) and annihilate in the evacuation funnel of the ergospheric jet against background photons.…”