Stellar Mass Spectra from Non-Isothermal Gravoturbulent Fragmentation

Abstract

(abridged version) Identifying the processes that determine the initial mass function of stars (IMF) is a fundamental problem in star formation theory. One of the major uncertainties 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 effect of a piecewise polytropic EOS on the formation of stellar clusters in turbulent, self-gravitating molecular clouds. We increase the polytropic exponent gamma from 0.7 to 1.1 at some chosen density n_c, which we vary from from 4.3x10^4 cm^-3 to 4.3x10^7 cm^-3. The change of thermodynamic state at n_c selects a characteristic mass scale for fragmentation M_ch, which we relate to the peak of the observed IMF. We find a relation M_ch ~ n_c^-0.5, supporting the idea that the distribution of stellar masses largely depends on the thermodynamic state of the star-forming gas.

7 pages, including 2 figures: invited talk presented at the conference on "IMF@50: The Stellar Initial Mass Function Fifty Years Later" held at Abbazia di Spineto, Siena, Italy, May 2004; to be published by Kluwer Academic Publishers, edited by E. Corbelli, F. Palla, and H. Zinnecker

References in corpus (7)

• Galactic Stellar and Substellar Initial Mass Function
• Embedded Clusters in Molecular Clouds
• Control of star formation by supersonic turbulence
• The Physics of Star Formation
• The Formation of Stellar Clusters in Turbulent Molecular Clouds: Effects of the Equation of State
• Effects of the Equation of State on the Formation of Star Clusters
• Quiescent and coherent cores from gravoturbulent fragmentation

Cited by in corpus (23)

• Theory of Star Formation
• A Minimum Column Density of 1 g cm^-2 for Massive Star Formation
• Fragmentation of star-forming clouds enriched with the first dust
• A robust numerical scheme for highly compressible magnetohydrodynamics: Nonlinear stability, implementation and tests
• Gravitational fragmentation and the formation of brown dwarfs in stellar clusters
• The Jeans mass and the origin of the knee in the IMF
• The dependence of star formation on initial conditions and molecular cloud structure
• Brown dwarfs and very low mass stars in the Hyades cluster : a dynamically evolved mass function
• Fragmentation in Molecular Clouds and its connection to the IMF
• Metals, dust and the cosmic microwave background: fragmentation of high-redshift star-forming clouds
• The effect of the dynamical state of clusters on gas expulsion and infant mortality
• The relationship between the prestellar core mass function and the stellar initial mass function
• The Stellar Mass Spectrum in Warm and Dusty Gas: Deviations from Salpeter in the Galactic Centre and in Circum-Nuclear Starburst Regions
• Magnetic fields at the onset of high-mass star formation
• Formation of the first stars
• Binary formation and mass function variations in fragmenting discs with short cooling times
• ALMA reveals the magnetic field evolution in the high-mass star forming complex G9.62+0.19
• The Role of Column Density in the Formation of Stars and Black Holes
• The initial conditions of star formation: cosmic rays as the fundamental regulators
• Astrophysics in 2005
• The formation of the first galaxies and the transition to low-mass star formation
• Numerical Methods for Simulating Star Formation
• The Numerical Simulation of Turbulence