Magnetic field morphology and evolution in the Central Molecular Zone and its effect on gas dynamics
Artikel i vetenskaplig tidskrift, 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
Författare
Robin G. Tress
Observatoire de Sauverny
Mattia C. Sormani
Universita degli Studi dell'Insubria
University of Surrey
P. Girichidis
Universität Heidelberg
S. C.O. Glover
Universität Heidelberg
R. S. Klessen
Universität Heidelberg
R. Smith
University of St Andrews
University of Manchester
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
Universität Heidelberg
L. Colzi
Centro de Astrobiologia (CAB)
C. Federrath
ARC Centre of Excellence for All-sky Astrophysics
Australian National University
P. García
Chinese Academy of Sciences
Universidad Catolica del Norte
A. Ginsburg
University of Florida
J. Göller
Universität Heidelberg
H. P. Hatchfield
University of Connecticut
California Institute of Technology (Caltech)
C. Henkel
Max-Planck-Gesellschaft
P. Hennebelle
Université Paris-Saclay
Jonathan D. Henshaw
Max-Planck-Gesellschaft
Liverpool John Moores University
Michaela Hirschmann
Observatoire de Sauverny
Osservatorio Astronomico di Trieste
Y. Hu
University of Wisconsin
J. K. F. Mann
Massachusetts Institute of Technology (MIT)
J.M. Diederik Kruijssen
Technische Universität München
COOL Research DAO
A. Lazarian
University of Wisconsin
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, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik
T. Pillai
Massachusetts Institute of Technology (MIT)
Víctor M. Rivilla
Centro de Astrobiologia (CAB)
A. Sanchez-Monge
Consejo Superior de Investigaciones Científicas (CSIC)
Centre Tecnològic de Telecomunicacions de Catalunya (CTTC)
J. D. Soler
Istituto nazionale di astrofisica (INAF)
D. Whitworth
Universidad Nacional Autónoma de México
Universität Heidelberg
Q. Zhang
Harvard-Smithsonian Center for Astrophysics
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 691 A303Ämneskategorier (SSIF 2011)
Astronomi, astrofysik och kosmologi
DOI
10.1051/0004-6361/202450035