Star formation takes place in the densest and coldest gas in a galaxy, in so-called molecular clouds (MCs). MCs do not evolve in isolation but are highly dynamical objects, which are born, fed, heated, and stirred from their turbulent environment into which they eventually dissolve. They form in regions where the hot or warm, ionized and atomic interstellar medium (ISM) condenses into cold ($T < 300K$), molecular gas. Often concentrated to the midplane of galactic disks, this process involves metallicity-dependent, non-equilibrium chemistry and molecule formation, heating and cooling, turbulence, self-gravity, and magnetic fields. Once formed, MCs further collapse to form stars and star clusters.
Less than 1% of all new-born stars are more massive than 8 solar masses, but these are particularly important for galaxy evolution. The life and death of massive stars differ intriguingly from those of their low-mass counterparts. Such stars affect their environment dramatically through their strong UV radiation, their energetic stellar wind, and their final explosion as a supernova (SN). These ’feedback’ processes generate turbulence in the parental molecular cloud, dissociate, ionize, and eventually destroy them from within, thereby preventing further star formation. Stellar feedback is thus thought to regulate the star formation efficiency in molecular clouds leading to a self-regulation of star formation on galactic scales.
In the framework of the Gauss project "SILCC" (Simulating the Life Cycle of Molecular Clouds) run on SuperMUC, the peta-scale machine at the Leibniz Rechenzentrum Garching, scientists from from Cologne, Garching, Heidelberg, Prague and Zurich model representative regions of disk galaxies using adaptive, three-dimensional simulations with the necessary physical complexity to follow the full life-cycle of molecular clouds. These simulations include self-gravity, magnetic fields, heating and cooling at different gas metallicities, molecule formation and dissociation, and stellar feedback. The ultimate goal of the SILCC project is to provide a self-consistent answer as to how stellar feedback regulates the star formation efficiency of a galaxy, how molecular clouds are formed and destroyed, and how galactic outflows are driven.
The SILCC project is split into several sets of simulations including different physical processes and different numerical realisations. Future simulations will be made public together with the corresponding scientific publication.
In the first set of simulations (see below) we show the impact of different supernova positioning and different (but constant in time) supernova rates on the structural evolution of the ISM in a galactic disc with a gas surface density of 10 Msun/pc² . For more information on the simulations please check the SILCC Paper.
SN rate [1/Myr]
Different driving schemes and supernova rates
|S10-lowSN-mix||5||mixed driving, ratio 1:1|
|S10-KS-mix||15||mixed driving, ratio 1:1||Movie|
|S10-highSN-mix||45||mixed driving, ratio 1:1|
|S10-KS-clus2||15||clustered driving; Type II SNe||Movie|
|S10-KS-clus||15||clustered driving; 20% of all SNe is Type Ia||Movie|
MHD runs with B0 = 3 microGauss
|S10-KS-clus-mag3||15||clustered driving; 20% of all SNe is Type Ia||Movie|
|Supernovae, Stellar winds||Movie|
|Supernovae, Stellar winds, Radiation||Movie|
|The DFG Priority Programme 1573 'Physics of the ISM'|
|Gauss Center for Supercomputing: Link to a short project description on the GCS site|
|Max Planck Computing and Data Facility (MPCDF)|