Adaptive Calculation of a Collapsing Molecular Cloud Core: The Jeans Condition

Abstract

In 1997 Truelove et al. introduced the Jeans condition to determine what level of spatial resolution is needed to avoid artificial fragmentation during protostellar collapse calculations. They first found using a Cartesian code based on an adaptive mesh refinement (AMR) technique that a Gaussian cloud model collapsed isothermally to form a singular filament rather than a binary or quadruple protostellar system as predicted by previous calculations. Recently Boss et al. in 2000 using a different hydrodynamics code with high spatial resolution reproduced the filamentary collapse solution of Truelove et al., implying that high resolution coupled with the Jeans condition is necessary to perform reliable calculations of the isothermal protostellar collapse. Here we recalculate the isothermal Gaussian cloud model of Truelove et al. and Boss et al. using a completely different code based on zooming coordinates to achieve the required high spatial resolution. We follow the collapse through 7 orders of magnitude increase in density and reproduce the filamentary solution. With the zooming coordinates, we are allowed to perform an adaptive calculation with a much lower computational cost than the AMR technique and other grid redefinition methods.