Magnetic field morphology and evolution in the Central Molecular Zone and its effect on gas dynamics

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 ɀ = 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 σ ɀ = 5 km s −1 on scales of 20 pc in the CMZ ring. The MRI alone sustains a velocity dispersion of σ ɀ ≃ 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 B ≃ 102 ( n /10 3 cm −3 ) 0.33 µ G. Finally, we discuss the implications of our results within the observational context in the CMZ.

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Publication Details

Journal
Astronomy and Astrophysics
Published
2024-10-02
DOI
https://doi.org/10.1051/0004-6361/202450035
Citations
21
Primary Topic
Astro and Planetary Science
Type
article
Field-Weighted Citation Impact
6.96

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Magnetic field morphology and evolution in the Central Molecular Zone and its effect on gas dynamics

R.S. Klessen, Jens Kauffmann, Laura Colzi, Yue Hu et al.
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Astronomy and Astrophysics
Astro and Planetary Science
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article

Magnetic field morphology and evolution in the Central Molecular Zone and its effect on gas dynamics

R.S. Klessen, Jens Kauffmann, Laura Colzi, Yue Hu, Christoph Federrath, F. Nogueras-Lara, S.C.O. Glover, Maya A. Petkova, V. M. Rivilla, A. Lazarian, J. M. Diederik Kruijssen, Ashley T. Barnes, Adam Ginsburg, S. N. Longmore, P. Hennebelle, David J Whitworth, Á. Sánchez-Monge, H Perry Hatchfield, Cara Battersby, M. Morris, Mattia C. Sormani, Lucia Armillotta, Noé Brucy, J. D. Henshaw, C. Henkel, T. Pillai, Dani Lipman, Robin G. Treß, Emanuele Sobacchi, Philipp Girichidis, Michaela Hirschmann, Kamran R J Bogue, J. Göller, Qizhou Zhang, Rowan J. Smith, P. García, J. D. Soler
article en
21 citations

Abstract

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 ɀ = 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 σ ɀ = 5 km s −1 on scales of 20 pc in the CMZ ring. The MRI alone sustains a velocity dispersion of σ ɀ ≃ 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 B ≃ 102 ( n /10 3 cm −3 ) 0.33 µ G. Finally, we discuss the implications of our results within the observational context in the CMZ.

Astronomy and AstrophysicsVol. 691
University of Insubria (IT), Australian National University (AU), Centre National de la Recherche Scientifique (FR), European Southern Observatory (DE), Jet Propulsion Laboratory (US), University of Wisconsin–Madison (US), University of Connecticut (US), University of California, Los Angeles (US), University of St Andrews (GB), Princeton University (US), Université Paris Cité (FR), Heidelberg University (DE), Commissariat à l'Énergie Atomique et aux Énergies Alternatives (FR), Université Paris-Saclay (FR), Trieste Astronomical Observatory (IT), Brera Astronomical Observatory (IT), Universidad Católica del Norte (CL), University of Surrey (GB), University of Manchester (GB), University of Florida (US), Astrophysique, Instrumentation et Modélisation (FR), ASTRO-3D (AU), Institut d'Estudis Espacials de Catalunya (ES), Excellence Cluster Origins (DE), Institute for Space Astrophysics and Planetology (IT), Max Planck Institute for Astronomy (DE), Institute of Space Sciences (ES), Université Bourgogne Franche-Comté (FR), Center for Astrophysics Harvard & Smithsonian (US), CEA Paris-Saclay (FR), Centro de Astrobiología (ES), ARC Centre of Excellence for All-sky Astrophysics (AU), Max Planck Institute for Radio Astronomy (DE), National Astronomical Observatories (CN), École Polytechnique Fédérale de Lausanne (CH), Technical University of Munich (DE), Liverpool John Moores University (GB), Chalmers University of Technology (SE)
National Science Foundation, National Aeronautics and Space Administration, Ministerio de Ciencia, Innovación y Universidades, Chinese Academy of Sciences South America Center for Astronomy, International Max Planck Research School for Environmental, Cellular and Molecular Microbiology, Royal Society, Marie Curie, European Commission, Deutsche Forschungsgemeinschaft, Chinese Academy of Sciences, Ministerio de Ciencia e Innovación, International Max Planck Research School for Advanced Methods in Process and Systems Engineering, Agencia Nacional de Investigación y Desarrollo, Science and Technology Facilities Council, European Research Council, Comisión Nacional de Investigación Científica y Tecnológica, Consejo Superior de Investigaciones Científicas, European Regional Development Fund, Agencia Estatal de Investigación, European Social Fund
Openalex Percentile: Top 3%
Astro and Planetary Science
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