AAS 203rd Meeting, January 2004
Session 7 Star Formation
Poster, Monday, January 5, 2004, 9:20am-6:30pm, Grand Hall

[7.06] Effects of a Piecewise Polytropic Equation of State on Turbulent Fragmentation

A.-K. Jappsen (Astrophysikalisches Institut Potsdam, Germany), Y. Li (Columbia University), M.-M. Mac Low (American Museum of Natural History), R. S. Klessen (Astrophysikalisches Institut Potsdam, Germany)

We study the effect of a piecewise polytropic equation of state on the formation of stellar clusters in turbulent, self-gravitating molecular clouds using three-dimensional, smoothed particle hydrodynamics simulations. We use the publicly available parallel code GADGET (Springel et al. 2001) in which we have implemented sink particles that can replace high-density gas cores, and with a uniform turbulent driving field.

Recently several of us conducted a systematic study of the effects of a varying polytropic index~\gamma on turbulent fragmentation. Their results showed that \gamma determines how strongly self-gravitating gas fragments. However in their computation, \gamma was left strictly constant in each simulation. In this study we extend our previous work by using a piecewise polytropic equation of state changing \gamma at some chosen density. We investigate if a change in \gamma determines the characteristic mass of the gas clump spectrum and thus perhaps the turn-over mass of the IMF. Preliminary results changing \gamma from 0.7 to 1.1 seem to corroborate this hypothesis, but with a weaker than expected dependence on the chosen density. We conduct a parameter study on the density at which \gamma changes to specify its effect on the resulting mass spectra.

AKJ acknowledges support by the Kade Fellowship. M-MML acknowledges support by NSF CAREER grant AST99-85392. AKJ and RSK acknowledge support by the Emmy Noether Program of the Deutsche Forschungsgemeinschaft KL1385/1.