Simulating star formation in molecular cloud cores. I. The influence of low levels of turbulence on fragmentation and multiplicity

By S. Goodwin, A. Whitworth, D. Ward-Thompson. 2003

172 citations recorded by the source corpus.

We present the results of an ensemble of simulations of the collapse and fragmentation of dense star-forming cores. We show that even with very low levels of turbulence the outcome is usually a binary, or higher-order multiple, system. We take as the initial conditions for these simulations a typical low-mass core, based on the average properties of a large sample of observed cores. All the simulated cores start with a mass of Mtotal = 5.4 M� , a flattened central density profile, a ratio of thermal to gravitational energy αtherm = 0.45 and a ratio of turbulent to gravitational energy αturb = 0.05 . Even this low level of turbulence - much lower than in most previous simulations - is sufficient to produce multiple star formation in 80% of the cores; the mean number of stars and brown dwarfs formed from a single core is 4.55, and the maximum is 10. At the outset, the cores have no large-scale rotation. The only difference between each individual simulation is the detailed structure of the turbulent velocity field. The multiple systems formed in the simulations have properties consistent with observed multiple systems. Dynamical evolution tends preferentially to eject lower mass stars and brown dwarves whilst hardening the remaining binaries so that the median semi-major axis of binaries formed is ∼30 AU. Ejected objects are usually single low-mass stars and brown dwarfs, yielding a strong correlation between mass and multiplicity. Brown dwarves are ejected with a higher average velocity than stars, and over time this should lead to mass segregation in the parent cluster. Our simulations suggest a natural mechanism for forming binary stars that does not require large-scale rotation, capture, or large amounts of turbulence.

Subfields: Astronomy and Astrophysics, Atmospheric Science

View Paper: https://www.semanticscholar.org/paper/d736db4c20e5533c36c4a6f71e315fcd6d758d04

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Citations in the corpus

The properties of brown dwarfs and low-mass hydrogen-burning stars formed by disc fragmentation (2008, methodology): “Gravo-turbulent fragmentation of collapsing prestellar cores may also produce BDs. Simulations (e.g. Bate et al. 2003; Goodwin et al. 2004a,b, 2006) of collapsing turbulent cores produce both HBs and BDs, with numbers in good agreement with observation.”
Physical Processes in the Interstellar Medium (2014, background): “Otherwise the core is likely to fragment (Goodwin et al., 2004a,b, 2006; Holman et al., 2013).”
Radiative transfer and the energy equation in SPH simulations of star formation (2007, methodology): “We use theSPH code (Goodwin et al. 2004a, b). uses variable smoothing lengths,hi, adjusted so that the number of neighbours is exactlyNNEIB = 50; it is important to have a constant number of neighbours to minimise numerical diffusion (Attwood et al. 2007).”
THE FORMATION OF LOW-MASS BINARY STAR SYSTEMS VIA TURBULENT FRAGMENTATION (2010, methodology): “Simulations often circumvent this difficulty by modeling individual dense cores with simple initial conditions (e.g., Klessen & Burkert 2000; Goodwin et al. 2004; Walch et al. 2009).”
Stellar, brown dwarf and multiple star properties from hydrodynamical simulations of star cluster formation (2008, background): “…of small N−body (e.g., McDonald & Clarke 1993, 1995; Sterzik & Durisen 1998, 2003; Hubber & Whitworth 2005) or hydrodynamical (e.g., Delgado-Donate et al. 2004; Goodwin et al. 2004b,c) simulations, with some of the observed trends in properties being reproduced depending on the input parameters.”
Global Models for the Evolution of Embedded, Accreting Protostellar Disks (2007, background): “Although multidimensional simulations provide a much more detailed view of disk formation and evolution during the embedded phase (e.g. Goodwin et al. 2004; Krumholz et al. 2007b), their high computational cost and the limited range of physical processes they include mean that these simulations can…”