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Simulations of the Milky Way’s central molecular zone – I. Gas dynamics

Tress, Robin G., Sormani, Mattia C., Glover, Simon C. O., Klessen, Ralf S., Battersby, Cara D., Clark, Paul C., Hatchfield, H. Perry and Smith, Rowan J. 2020. Simulations of the Milky Way’s central molecular zone – I. Gas dynamics. Monthly Notices of the Royal Astronomical Society 499 (3) , pp. 4455-4478. 10.1093/mnras/staa3120

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Abstract

We use hydrodynamical simulations to study the Milky Way’s central molecular zone (CMZ). The simulations include a non-equilibrium chemical network, the gas self-gravity, star formation, and supernova feedback. We resolve the structure of the interstellar medium at sub-parsec resolution while also capturing the interaction between the CMZ and the bar-driven large-scale flow out to R∼5kpc⁠. Our main findings are as follows: (1) The distinction between inner (R ≲ 120 pc) and outer (120 ≲ R ≲ 450 pc) CMZ that is sometimes proposed in the literature is unnecessary. Instead, the CMZ is best described as single structure, namely a star-forming ring with outer radius R ≃ 200 pc which includes the 1.3° complex and which is directly interacting with the dust lanes that mediate the bar-driven inflow. (2) This accretion can induce a significant tilt of the CMZ out of the plane. A tilted CMZ might provide an alternative explanation to the ∞-shaped structure identified in Herschel data by Molinari et al. (3) The bar in our simulation efficiently drives an inflow from the Galactic disc (R ≃ 3 kpc) down to the CMZ (R ≃ 200 pc) of the order of 1M⊙yr−1⁠, consistent with observational determinations. (4) Supernova feedback can drive an inflow from the CMZ inwards towards the circumnuclear disc of the order of ∼0.03M⊙yr−1⁠. (5) We give a new interpretation for the 3D placement of the 20 and 50 km s−1 clouds, according to which they are close (R ≲ 30 pc) to the Galactic Centre, but are also connected to the larger scale streams at R ≳ 100 pc.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Publisher: Oxford University Press
ISSN: 0035-8711
Date of First Compliant Deposit: 10 December 2020
Date of Acceptance: 6 October 2020
Last Modified: 11 Dec 2020 12:45
URI: http://orca.cf.ac.uk/id/eprint/136928

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