Jet in jet in M87

TL;DR

High-resolution VLBI observations of M87 reveal a triple-ridge jet structure, suggesting a nested jet system with potential dual-launch mechanisms linked to the black hole and accretion disk, supported by a relativistic MHD model.

Contribution

This study presents the first observational evidence of a triple-ridge jet structure in M87 and proposes a novel jet-in-jet model with a unipolar inductor mechanism.

Findings

Discovery of a persistent triple-ridge transverse structure.

Proposal of a nested jet model with an inner and outer jet.

Magnetic field strength of 80 G at the jet base inferred.

Abstract

New high-resolution Very Long Baseline Interferometer observations of the prominent jet in the M87 radio galaxy show a persistent triple-ridge structure of the transverse 15-GHz profile with a previously unobserved ultra-narrow central ridge. This radio structure can reflect the intrinsic structure of the jet, so that the jet as a whole consists of two embedded coaxial jets. A relativistic magnetohydrodynamic model is considered in which an inner jet is placed inside a hollow outer jet and the electromagnetic fields, pressures and other physical quantities are found. The entire jet is connected to the central engine that plays the role of a unipolar inductor generating voltage between the jets and providing opposite electric currents, and the charge neutrality and current closure together with the electromagnetic fields between the jets can contribute to the jet stabilization. The constant voltage is responsible for the similar widening laws observed for the inner and outer jets. This jet-in-jet structure can indicate simultaneous operation of two different jet-launching mechanisms, one relating to the central supermassive black hole and the other to the surrounding accretion disc. An inferred magnetic field of 80 G at the base is sufficient to provide the observed jet luminosity.