Visit ASIAA Homepage Deadline: February 15, 2016
M87 Workshop: Towards the 100th Anniversary of the Discovery of Cosmic Jets
May 23-27, 2016
Taipei, Taiwan

Poster Presentation

Structural Transition in the NGC 6251 Jet

Author(s): Chih-Yin Tseng et al. (ASIAA)

Presenter: Chih-Yin Tseng (ASIAA/NTU)

The jet structure of NGC 6251 at milliarcsecond and arcsecond scales is investigated utilizing images taken with the European VLBI Network, Very Large Array, and Very Long Baseline Array. A structural transition of the jet (from a parabolic to a conical shape) is discovered close to the sphere of gravitational influence (SGI) of the supermassive black hole (SMBH), at an axial distance of 2 × 10^5 times the Schwarzschild radius from the central engine. This result, following the case of M 87, suggests a fundamental mechanism of the active galactic nuclei jet collimation; a magnetohydrodynamic jet is subject to thermal confinement by the ambient gas that is under control of the SMBH gravity, but after propagating through the SGI it becomes a freely expanding stream on the galactic scale.

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