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Investigating Magnetic Activity in the Galactic Centre by Global MHD Simulation

Published online by Cambridge University Press:  09 February 2017

Takeru K. Suzuki ,
Yasuo Fukui ,
Kazufumi Torii ,
Mami Machida ,
Ryoji Matsumoto  and
Kensuke Kakiuchi
Takeru K. Suzuki
Affiliation:
School of Arts & Sciences, The University of Tokyo, 3-8-1, Komaba, Meguro, Tokyo, 153-8902, Japan email: stakeru@ea.c.u-tokyo.ac.jp Dept. of Physics, Nagoya University, Furo-cho, Chikusa, Nagoya, Aichi, 464-8602, Japan
Yasuo Fukui
Affiliation:
Dept. of Physics, Nagoya University, Furo-cho, Chikusa, Nagoya, Aichi, 464-8602, Japan
Kazufumi Torii
Affiliation:
Dept. of Physics, Nagoya University, Furo-cho, Chikusa, Nagoya, Aichi, 464-8602, Japan National Radio Observatory, National Astronomical Observatory of Japan, 462-2, Nobeyama, Minamimaki, Minamisaku, Nagano, 384-1305, Japan
Mami Machida
Affiliation:
Dept. of Physics, Faculty of Sciences, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
Ryoji Matsumoto
Affiliation:
Dept. of Physics, Graduate School of Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
Kensuke Kakiuchi
Affiliation:
Dept. of Physics, Nagoya University, Furo-cho, Chikusa, Nagoya, Aichi, 464-8602, Japan
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Abstract

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By performing a global magnetohydrodynamical (MHD) simulation for the Milky Way with an axisymmetric gravitational potential, we propose that spatially dependent amplification of magnetic fields possibly explains the observed noncircular motion of the gas in the Galactic centre (GC) region. The radial distribution of the rotation frequency in the bulge region is not monotonic in general. The amplification of the magnetic field is enhanced in regions with stronger differential rotation, because magnetorotational instability and field-line stretching are more effective. The strength of the amplified magnetic field reaches ≳ 0.5 mG, and radial flows of the gas are excited by the inhomogeneous transport of angular momentum through turbulent magnetic field that is amplified in a spatially dependent manner. As a result, the simulated position-velocity diagram exhibits a time-dependent asymmetric parallelogram-shape owing to the intermittency of the magnetic turbulence; the present model provides a viable alternative to the bar-potential-driven model for the parallelogram shape of the central molecular zone. In addition, Parker instability (magnetic buoyancy) creates vertical magnetic structure, which would correspond to observed molecular loops, and frequently excited vertical flows. Furthermore, the time-averaged net gas flow is directed outward, whereas the flows are highly time dependent, which would contribute to the outflow from the bulge.

Keywords

accretionaccretion disks–Galaxy: bulge–Galaxy: centre–Galaxy: kinematics and dynamics–magnetohydrodynamics (MHD)–turbulence
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 11 , Symposium S322: The Multi-Messenger Astrophysics of the Galactic Centre , July 2016 , pp. 137 - 140
Copyright
Copyright © International Astronomical Union 2017 

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