Resolution requirements for simulating gravitational fragmentation using SPH

Free access article

Issue		A&A Volume 450, Number 3, May II 2006


Page(s)		881 - 886
Section		Astrophysical processes
DOI		http://dx.doi.org/10.1051/0004-6361:20054100

A&A 450, 881-886 (2006)
DOI: 10.1051/0004-6361:20054100

Resolution requirements for simulating gravitational fragmentation using SPH

D. A. Hubber, S. P. Goodwin and A. P. Whitworth

School of Physics & Astronomy, Cardiff University, 5 The Parade, Cardiff CF24 3YB, Wales, UK
e-mail: David.Hubber@astro.cf.ac.uk

(Received 24 August 2005 / Accepted 1 December 2005)

Abstract
Jeans showed analytically that, in an infinite uniform-density isothermal gas, plane-wave perturbations collapse to dense sheets if their wavelength, $\lambda$ , satisfies $\lambda > \lambda_{_{\rm JEANS}} = \left(\pi a^2 / G \rho_{_0}\right)^{1/2}$ (where a is the isothermal sound speed and $\rho_{_0}$ is the unperturbed density); in contrast, perturbations with smaller $\lambda$ oscillate about the uniform density state. Here we show that Smoothed Particle Hydrodynamics reproduces these results well, even when the diameters of the SPH particles are twice the wavelength of the perturbation. Our simulations are performed in 3-D with initially settled (i.e. non-crystalline) distributions of particles. Therefore there exists the seed noise for artificial fragmentation, but it does not occur. We conclude that, although there may be - as with any numerical scheme - "skeletons in the SPH cupboard", a propensity to fragment artificially is evidently not one of them.

Key words: stars: formation -- methods: numerical -- hydrodynamics -- instabilities

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