The onset of large-scale turbulence in the interstellar medium of spiral galaxies
MetadataShow full item record
Turbulence is ubiquitous in the interstellar medium (ISM) of the Milky Way and other spiral galaxies. The energy source for this turbulence has been much debated with many possible origins proposed. The universality of turbulence, its reported large-scale driving, and that it occurs also in starless molecular clouds, challenges models invoking any stellar source. A more general process is needed to explain the observations. In this work, we study the role of galactic spiral arms. This is accomplished by means of three-dimensional hydrodynamical simulations which follow the dynamical evolution of interstellar diffuse clouds (similar to 100 cm-3) interacting with the gravitational potential field of the spiral pattern. We find that the tidal effects of the arm's potential on the cloud result in internal vorticity, fragmentation and hydrodynamical instabilities. The triggered turbulence results in large-scale driving, on sizes of the ISM inhomogeneities, i.e. as large as similar to 100 pc, and efficiencies in converting potential energy into turbulence in the range similar to 10-25 per cent per arm crossing. This efficiency is much higher than those found in previous models. The statistics of the turbulence in our simulations are strikingly similar to the observed power spectrum and Larson scaling relations of molecular clouds and the general ISM. The dependence found from different models indicate that the ISM turbulence is mainly related to local spiral arm properties, such as its mass density and width. This correlation seems in agreement with recent high angular resolution observations of spiral galaxies, e.g. M51 and M33.
Falceta-Goncalves , D , Bonnell , I , Kowal , G , Lepine , J R D & Braga , C A S 2015 , ' The onset of large-scale turbulence in the interstellar medium of spiral galaxies ' Monthly Notices of the Royal Astronomical Society , vol 446 , no. 1 , pp. 973-989 . DOI: 10.1093/mnras/stu2127
Monthly Notices of the Royal Astronomical Society
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
DFG thanks the European Research Council (ADG-2011 ECOGAL), and Brazilian agencies CAPES (3400-13-1) and FAPESP (no.2011/12909-8) for financial support. IB acknowledges the European Research Council (ADG-2011 ECOGAL) for financial support. GK acknowledges support from FAPESP (grants no. 2013/04073-2 and 2013/18815-0).
Items in the St Andrews Research Repository are protected by copyright, with all rights reserved, unless otherwise indicated.
Showing items related by title, author, creator and subject.
Spectral non-locality, absolute equilibria and Kraichnan-Leith-Batchelor phenomenology in two-dimensional turbulent energy cascades Burgess, B. H.; Shepherd, T. G. (2013-06) - Journal articleWe study the degree to which Kraichnan-Leith-Batchelor (KLB) phenomenology describes two-dimensional energy cascades in alpha turbulence, governed by δθ/δt + J(ψ, θ) = ν ∇2θ + f, where θ = (-Δ)α/2ψ is generalized vorticity, ...
Falceta-Goncalves, D.; Kowal, G.; Falgarone, E.; Chian, A. C. -L. (2014-05-16) - Journal articleTurbulence is ubiquitous in the insterstellar medium and plays a major role in several processes such as the formation of dense structures and stars, the stability of molecular clouds, the amplification of magnetic fields, ...
Tran, Chuong Van; Dritschel, David Gerard (2006-03-25) - Journal articleThe behaviour of turbulent flows within the single-layer quasi-geostrophic (Charney-Hasegawa-Mima) model is shown to be strongly dependent on the Rossby deformation wavenumber lambda (or free-surface elasticity). Herein, ...