| 1 | [[CollapsibleStart(Fedderath, et al. (‘10))]] |
| 2 | |
| 3 | [http://adsabs.harvard.edu/abs/2010ApJ...713..269F Modeling Collapse and Accretion in Turbulent Gas Clouds: Implementation and Comparison of Sink Particles in AMR and SPH] |
| 4 | |
| 5 | === Background === |
| 6 | |
| 7 | The numerical difficulty with modeling the collapse of a clump, while keeping track of the entire cloud, is given by the fact that the free-fall time, Tff, where |
| 8 | |
| 9 | {{{#!latex |
| 10 | $ Tff = (3\pi / 32G\rho)^{1/2} $ |
| 11 | }}} |
| 12 | |
| 13 | decreases with increasing density and so resolution of the subgrids is demanded over many dynamical time scales. The two methods thus far designed to deal with this matter are 'Jeans heating' and 'sink particles'. Sink particles are a more realistic methodology and was first developed for SPH by Bate et al. ('95). The algorithm was later adapted by Krumholz et al. ('04) for Eulerian AMR. This paper describes a more rigorous series of checks for sink formation. |
| 14 | |
| 15 | === Sink Implentation === |
| 16 | |
| 17 | Sink particles enable the star formation rate/star formation efficiency, and mass distribution, to be addressed in a robust and quantitative way. |
| 18 | |
| 19 | Sink algorithms originated from the notion of a density threshold. In earlier work, such a threshold was defined, and once surpassed, a sink particle was placed in the grid. |
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| 21 | The present work, however, have added in addition to this criterion, a series of checks to insure that sinks are formed only in gravitationally bound and collapsing structures. These are listed as follows: |
| 22 | |
| 23 | * Converging flow |
| 24 | * Bound system |
| 25 | * Jean's unstable |
| 26 | * Gravitational potential minima |
| 27 | |
| 28 | Else, under conditions such as shear, a sink may erroneously form. |
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| 30 | |