Formation of limb-brightened radio jets by angle-dependent energy extraction from rapidly rotating black holes

Kouichi HIROTANI^1*, Hsien Shang¹, Ruben Krasnopolsky¹, Kenichi Nishikawa²

¹ASIAA, Academia Sinica, Taipei, Taiwan
²Physics, Chemistry and Mathematics, Alabama, USA

* Presenter:Kouichi HIROTANI, email:hirotani@asiaa.sinica.edu.tw

By general relativistic magnetohydrodynamic simulations, it is suggested that the rotational energy of a rapidly rotating black hole (BH)
is preferentially extracted along the magnetic field lines threading the event horizon in the middle and lower latitudes.
Applying this angle-dependent Poynting flux to the jet downstream, we demonstrate that the jets exhibit limb-brightened structures for various viewing angles, as observed from Mrk 501, M87, and Cyg A between 5 and 75 degrees, and that the limb-brightening is enhanced when the jet is collimated strongly. It is also found that the jet width perpendicular to the propagation direction shrinks at the projected distance of the altitude where the jet collimates from a conical shape (near the BH) to a parabolic one (in the jet). Comparing with the VLBI observations, we show this collimation takes place around the de-projected altitude of 100 Schwarzschild radii from the BH in the case of the M87 jet.

Keywords: black holes, general relativity, magnetohydrodynamics, very long baseline interferometry, electron-positron pair plasma