Accretion-driven turbulence as universal process: galaxies, molecular clouds, and protostellar disks

By Ralf Klessen, P. Hennebelle. 2009

240 citations recorded by the source corpus.

Context. Even though turbulent motions are found everywhere in astrophysical systems, the origin of this turbulence is poorly understood. When cosmic structures form, they grow in mass via accretion from their surrounding environment. Aims. We propose that accretion is able to drive internal turbulent motions in a wide range of astrophysical objects and study this process in the case of galaxies, molecular clouds, and protoplanetary disks. Methods. We use a combination of numerical simulations and analytical arguments to predict the level of turbulence as a function of the accretion rate, the dissipation scale, and the density contrast, and compare our models with observational data. Results. We find that in Milky Way type galaxies the observed level of turbulence in the interstellar medium can be explained by accretion, provided that the galaxies gain mass at a rate comparable to the rate at which they form stars. This process is particularly relevant in the extended outer disks beyond the star-forming radius. For it to drive turbulence in dwarf galaxies, the accretion rate needs to exceed the star formation rate by a large factor, so we expect other sources to dominate. We also calculate the rate at which molecular clouds grow in mass when they build up from the atomic component of the galactic gas and find that their internal turbulence is likely to be driven by accretion as well. It is the very process of cloud formation that excites turbulent motions on small scales by establishing the turbulent cascade. In the case of T Tauri disks, we show that accretion can drive subsonic turbulence if the rate at which gas falls onto the disk is comparable to the rate at which disk material accretes onto the central star. This also explains the observed relation of accretion rate and stellar mass, u M ∝ M 1.8 � .T he efficiency required to convert infall motion into turbulence is a few percent in all three cases. Conclusions. We conclude that accretion-driven turbulence is a universal concept with far-reaching implications for a wide range of astrophysical objects.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/5834521e2790644f45c727b553a1ac32f0df4208

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Citations in the corpus

A NEW JEANS RESOLUTION CRITERION FOR (M)HD SIMULATIONS OF SELF-GRAVITATING GAS: APPLICATION TO MAGNETIC FIELD AMPLIFICATION BY GRAVITY-DRIVEN TURBULENCE (2011, background): “Recently, Klessen & Hennebelle (2010), Elmegreen & Burkert (2010), and Vazquez-Semadeni (2010) suggested that a universal source for driving astrophysical turbulence everywhere from cosmic scales and galaxies, over galactic clouds, down to individual proto-stellar disks is the accretion from their…”
Small-scale dynamo action during the formation of the first stars and galaxies - I. The ideal MHD limit (2010, methodology): “Under such conditions, the injection scale of turbulence is usually comparable to the size of the system under consideration (Klessen & Hennebelle 2010).”
Cluster-formation in the Rosette molecular cloud at the junctions of filaments (2012, unknown): “Large-scale turbulence, even on a Galactic scale (Mac Low & Klessen 2004), can be excited by expanding supernova shells, colliding flows forming clouds, or globally by any form of accretion (Klessen & Hennebelle 2010).”
PHYSICAL PROPERTIES OF MOLECULAR CLOUDS FOR THE ENTIRE MILKY WAY DISK (2016, background): “Klessen & Hennebelle (2010) suggested that gas accretion is the main process that maintains turbulence at the scale of a galaxy, of a molecular cloud, and of a protoplanetary disk.”
THE STAR FORMATION RATE OF TURBULENT MAGNETIZED CLOUDS: COMPARING THEORY, SIMULATIONS, AND OBSERVATIONS (2012, background): “…well as compression of ISM gas in galactic spiral shocks (Elmegreen 2009) and gravitational contraction (Hoyle 1953; Vazquez-Semadeni et al. 1998; Klessen & Hennebelle 2010; Elmegreen & Burkert 2010; Federrath et al. 2011c) are likely exciting a considerable amount of compressible modes that…”
SDC13 infrared dark clouds: longitudinally collapsing filaments? (2013, background): “The velocity dispersion resulting from gravitational energy conversion is then a function of the infall velocity and the gas density (Klessen & Hennebelle 2010).”
Turbulent molecular clouds (2012, methodology): “3 shows a snapshot (column density, density, temperature and magnetic field cut) of a colliding flow simulation (similar to what is presented in Hennebelle et al. 2008 and Klessen & Hennebelle 2010) aiming at forming a molecular cloud.”
On the universality of supersonic turbulence (2013, background): “…2011; Lee, Murray & Rahman 2012), gravitational collapse and accretion of material (Vazquez-Semadeni, Canto & Lizano 1998; Elmegreen & Burkert 2010; Klessen & Hennebelle 2010; VázquezSemadeni et al. 2010; Federrath et al. 2011b; Robertson & Goldreich 2012; Choi, Shlosman & Begelman 2013), and…”
ON THE STAR FORMATION EFFICIENCY OF TURBULENT MAGNETIZED CLOUDS (2012, background): “For instance, Klessen & Hennebelle (2010) have argued and Federrath et al. (2011c) have shown that collapse and accretion do drive turbulence, but at the same time, the turbulence produced in this conversion from gravitational energy cannot hold the collapse.”
AN IMPRINT OF MOLECULAR CLOUD MAGNETIZATION IN THE MORPHOLOGY OF THE DUST POLARIZED EMISSION (2013, methodology): “The behavior of turbulence in the ISM is still subject of study (Klessen & Hennebelle 2010; Schneider et al. 2011; Hennebelle & Falgarone 2012) and the continuous energy input is an approximation used to add up multiple snapshots and improve statistics in the study of the power spectrum or…”
Global hierarchical collapse in molecular clouds. Towards a comprehensive scenario (2019, background): “On the other hand, the possibility of external driving has been favored by numerical simulations of cloud formation by converging flows in the warm neutral medium (WNM) (e.g., Vázquez-Semadeni et al. 2007, 2010; Heitsch & Hartmann 2008; Klessen & Hennebelle 2010; Micic et al. 2013).”
Why are most molecular clouds not gravitationally bound (2011, background): “The internal kinematics of these clouds could be due to cloud-cloud collisions or large scale flows (Bonnell et al. 2006; Dobbs & Bonnell 2007; Klessen & Hennebelle 2010), and/or stellar feedback (e.g. Mac Low & Klessen 2004 and references therein).”
THREE-DIMENSIONAL HYDRODYNAMIC SIMULATIONS OF MULTIPHASE GALACTIC DISKS WITH STAR FORMATION FEEDBACK. I. REGULATION OF STAR FORMATION RATES (2013, background): “…Kim et al. 2006, 2010; Dobbs & Bonnell 2006), magnetorotational instability (Kim et al. 2003; Piontek & Ostriker 2005, 2007), large-scale gravitational instabilities (Wada & Norman 2002; Kim & Ostriker 2007; Agertz et al. 2009; Bournaud et al. 2010), and cosmic inflow (Klessen & Hennebelle 2010).”