EPoS Contribution
EPoS Contribution
First Core Lifetime from Low- to High-Mass Star Formation

Asmita Bhandare
MPIA, Heidelberg, DE
Stars are formed by the gravitational collapse of dense, gaseous and dusty cores within magnetized molecular clouds. Understanding the complexity of the numerous physical processes involved in the very early stages of star formation requires detailed thermodynamical modeling in terms of radiation transport and phase transitions. We perform core collapse simulations including the stages of first and second core formation in spherical symmetry. We use a gray treatment of radiative transfer coupled with hydrodynamics to simulate Larson's collapse. By incorporating a realistic gas equation of state via appropriate opacity tables and a density and temperature dependent adiabatic index and mean molecular weight, we model the associated phase transitions. We investigate the properties of Larson's first and second cores and expand these collapse studies for the first time to span a wide range of initial cloud masses from 1.0 Msun to 80 Msun. Thereby, we reveal a strong dependence of the first core properties on the initial cloud mass. We find that the first core radius and mass increase with the initial cloud mass in the low-mass regime until around 10 Msun and decrease towards the higher masses. Most importantly, the lifetime of first cores strongly decreases towards the intermediate and high-mass regime. In this talk I will demonstrate that low-mass protostars evolve through two distinct stages of formation of the first and second hydrostatic cores. In contrast, in the high-mass star formation regime, the collapsing cloud cores rapidly evolve through the first core phase and essentially immediately form Larson's second cores.
Caption: Thermal evolution (bottom left) showing the first and second collapse phase for a 1 Msun cloud. The change in effective gamma indicates the importance of using a realistic gas equation of state. The plot on the top right shows the dependence of the first core lifetime (i.e. time between the onset of formation of the first and second hydrostatic cores) on the initial cloud mass. The lifetime of first cores strongly decrease towards the intermediate and high-mass regime.
Collaborators:
R. Kuiper, IAAT, DE
Th. Henning , MPIA, DE
C. Fendt, MPIA, DE
G.D. Marleau, U Bern, CH
A. Koelligan, IAAT, DE
 Suggested Session: High-mass star/star cluster formation