EPoS Contribution
EPoS Contribution
Star Formation and Chemical Yields in Giant Molecular Clouds

Aake Nordlund
Niels Bohr Institute, Copenhagen, Denmark
The presence and initial abundances of short-lived radionuclides (SLRs; e.g., 26Al, 53Mn, 60Fe, 182Hf) in the Solar System can both be used to obtain evidence about the timescales of processes in the early Solar System, and to provide constraints on the larger scale environment where our Sun was formed. Many SLRs are believed to have a stellar origin, and may have either been inherited from the molecular cloud that the Sun was borne in, or may have been injected into the proto-solar molecular cloud core just prior to or contemporaneously with its collapse. In particular, recent high-precision measurements of the daughter product of 26Al (i.e. 26Mg) in meteorites and their components show that, despite its short half-life of 0.73 Ma, 26Al was present at levels of 26Al/27Al ~ 2.8e-5 at the birth of the Solar System. In order to use the information available from SLR analysis a good understanding of the transport and distribution of the SLRs in star-forming regions is needed, and we have set out to study these mechanisms using three-dimensional MHD models of star formation that keep track of yields from supernovae and stellar winds via additional passive scalar transport equations. We use both the RAMSES adaptive mesh refinement code and the uni-grid Stagger Code, enhanced with detailed ISM cooling and heating functions, and with tables of nuclear yields, stellar life times, stellar wind speeds and mass loads, as a function of stellar mass. Stars, represented by point masses with properties such as mass and life time, are created according to a standard IMF in the cold and dense local condensations (molecular clouds) that form in the larger environment, and the motions of massive stars are followed until such times as they explode as supernovae, giving back kinetic energy and chemical yields to the ISM. Using numerical simulations representative of giant molecular clouds with masses 1e5 to 1e6 solar masses, on scales ranging from 40 to 160 pc, we show that, contrary to widely held beliefs, the occurrence of 26Al at the levels deduced for the early solar system is a natural consequence of star formation under typical GMC conditions -- no special event such as a late chance injection of SLRs into the proto-solar nebula or proto-stellar disk is needed.
A. Vasileiadis
P. Padoan
T. Haugbølle