Stellar Mass Spectra from Non-Isothermal Gravoturbulent Fragmentation

Identifying the processes that determine the initial mass function of stars (IMF) is a fundamental problem in star formation theory. One of the major uncertain-ties is the exact chemical state of the star forming gas and its influence on the dynamical evolution. Most simulations of star forming clusters use an isothermal equation of state (EOS). We address these issues and study the e ff ect of a piecewise polytropic EOS on the formation of stellar clusters in turbulent, self-gravitating molecular clouds using three-dimensional, smoothed particle hydrodynamics simulations. In these simulations stars form via a process we call gravoturbulent fragmentation, i.e., gravitational fragmentation of turbulent gas. To approximate the results of published predictions of the thermal behavior of collapsing clouds, we increase the polytropic exponent γ from 0.7 to 1.1 at some chosen density n c , which we vary from from 4 . 3 × 10 4 cm − 3 to 4 . 3 × 10 7 cm − 3 . The change of thermodynamic state at n c selects a characteristic mass scale for fragmentation M ch , which we