Formation of Stellar Clusters and the Importance of Thermodynamics for Fragmentation

TL;DR

This paper explores how the thermodynamic properties of interstellar gas influence star cluster formation and fragmentation, affecting the initial mass function across different cosmic environments.

Contribution

It demonstrates the critical role of thermodynamics in star formation, linking gas physics to the stellar mass distribution and cluster properties.

Findings

Thermodynamic behavior determines fragmentation scales.

Transition in gas heating/cooling influences the IMF peak.

Simulations show universality of the IMF explained by physics.

Abstract

We discuss results from numerical simulations of star cluster formation in the turbulent interstellar medium (ISM). The thermodynamic behavior of the star-forming gas plays a crucial role in fragmentation and determines the stellar mass function as well as the dynamic properties of the nascent stellar cluster. This holds for star formation in molecular clouds in the solar neighborhood as well as for the formation of the very first stars in the early universe. The thermodynamic state of the ISM is a result of the balance between heating and cooling processes, which in turn are determined by atomic and molecular physics and by chemical abundances. Features in the effective equation of state of the gas, such as a transition from a cooling to a heating regime, define a characteristic mass scale for fragmentation and so set the peak of the initial mass function of stars (IMF). As it is based on fundamental physical quantities and constants, this is an attractive approach to explain the apparent universality of the IMF in the solar neighborhood as well as the transition from purely primordial high-mass star formation to the more normal low-mass mode observed today.