Magnetic field morphology and evolution in the Central Molecular Zone and its effect on gas dynamics
Journal article, 2024
The interstellar medium in the Milky Way's Central Molecular Zone (CMZ) is known to be strongly magnetised, but its large-scale morphology and impact on the gas dynamics are not well understood. We explore the impact and properties of magnetic fields in the CMZ using three-dimensional non-self gravitating magnetohydrodynamical simulations of gas flow in an external Milky Way barred potential. We find that: (1) The magnetic field is conveniently decomposed into a regular time-averaged component and an irregular turbulent component. The regular component aligns well with the velocity vectors of the gas everywhere, including within the bar lanes. (2) The field geometry transitions from parallel to the Galactic plane near z = 0 to poloidal away from the plane. (3) The magneto-rotational instability (MRI) causes an in-plane inflow of matter from the CMZ gas ring towards the central few parsecs of 0.01-0.1 M· yr-1 that is absent in the unmagnetised simulations. However, the magnetic fields have no significant effect on the larger-scale bar-driven inflow that brings the gas from the Galactic disc into the CMZ. (4) A combination of bar inflow and MRI-driven turbulence can sustain a turbulent vertical velocity dispersion of Ï∼ = 5 km s-1 on scales of 20 pc in the CMZ ring. The MRI alone sustains a velocity dispersion of Ï ∼ 3 km s-1. Both these numbers are lower than the observed velocity dispersion of gas in the CMZ, suggesting that other processes such as stellar feedback are necessary to explain the observations. (5) Dynamo action driven by differential rotation and the MRI amplifies the magnetic fields in the CMZ ring until they saturate at a value that scales with the average local density as Ba 102 (n/103 cm-3)0.33 μG. Finally, we discuss the implications of our results within the observational context in the CMZ.
Galaxy: kinematics and dynamics
Galaxy: center
ISM: magnetic fields
Author
Robin G. Tress
Observatoire de Sauverny
Mattia C. Sormani
University of Surrey
University of Insubria
P. Girichidis
Heidelberg University
S. C.O. Glover
Heidelberg University
R. S. Klessen
Heidelberg University
R. Smith
University of Manchester
University of St Andrews
E. Sobacchi
Istituto nazionale di astrofisica (INAF)
Lucia Armillotta
Princeton University
Ashley T. Barnes
European Southern Observatory (ESO)
C. Battersby
University of Connecticut
K. R.J. Bogue
University of Manchester
N. Brucy
Heidelberg University
L. Colzi
Centro de Astrobiologia (CAB)
C. Federrath
Australian National University
ARC Centre of Excellence for All-sky Astrophysics
P. García
Universidad Catolica del Norte
Chinese Academy of Sciences
A. Ginsburg
College of Liberal Arts and Sciences
J. Göller
Heidelberg University
H. P. Hatchfield
University of Connecticut
California Institute of Technology (Caltech)
C. Henkel
Max Planck Society
P. Hennebelle
University Paris-Saclay
Jonathan D. Henshaw
Liverpool John Moores University
Max Planck Society
Michaela Hirschmann
Osservatorio Astronomico di Trieste
Observatoire de Sauverny
Y. Hu
University of Wisconsin Madison
J. K. F. Mann
Massachusetts Institute of Technology (MIT)
J.M. Diederik Kruijssen
COOL Research DAO
Technical University of Munich
A. Lazarian
University of Wisconsin Madison
D. Lipman
University of Connecticut
S. Longmore
COOL Research DAO
Liverpool John Moores University
M. R. Morris
University of California
Francisco Nogueras-Lara
European Southern Observatory (ESO)
Maya Petkova
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
T. Pillai
Massachusetts Institute of Technology (MIT)
Víctor M. Rivilla
Centro de Astrobiologia (CAB)
A. Sanchez-Monge
Spanish National Research Council (CSIC)
Centre Tecnològic de Telecomunicacions de Catalunya (CTTC)
J. D. Soler
Istituto nazionale di astrofisica (INAF)
D. Whitworth
Universidad Nacional Autónoma de México
Heidelberg University
Q. Zhang
Harvard-Smithsonian Center for Astrophysics
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 691 A303Subject Categories (SSIF 2011)
Astronomy, Astrophysics and Cosmology
DOI
10.1051/0004-6361/202450035