The Jeans instability in smoothed particle hydrodynamics |
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| Authors: | Whitworth |
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| Institution: | Department of Physics &Astronomy, University of Wales, Cardiff CF2 3YB |
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| Abstract: | We derive analytically the Jeans criterion for a gas simulated using an SPH code in which the number of neighbours N neighb is held constant (approximately) and the gravity-softening length, ε, equals the smoothing length, h (approximately). We show that the Jeans criterion is reproduced accurately for resolved structures, i.e. those represented by > N neighb particles. Unresolved structures are stabilized, as long as (i) the smoothing kernel W ( u ) is sufficiently centrally peaked, and (ii) the Jeans mass is resolved. Provided that these conditions are satisfied, then, in simulations of the formation of stars and galaxies, any fragmentation that occurs should be both physical and resolved. In particular there should be no creation of sub-Jeans condensations owing to numerical instability. |
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| Keywords: | hydrodynamics methods: numerical stars: formation galaxies: formation large-scale structure of Universe |
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