Modeling jet and outflow feedback during star cluster formation
  Powerful jets and outflows are launched from the protostellar disks around
newborn stars. These outflows carry enough mass and momentum to transform the
structure of their parent molecular cloud and to potentially control star
formation itself. Despite their importance, we have not been able to fully
quantify the impact of jets and outflows during the formation of a star
cluster. The main problem lies in limited computing power. We would have to
resolve the magnetic jet-launching mechanism close to the protostar and at the
same time follow the evolution of a parsec-size cloud for a million years.
Current computer power and codes fall orders of magnitude short of achieving
this. In order to overcome this problem, we implement a subgrid-scale (SGS)
model for launching jets and outflows, which demonstrably converges and
reproduces the mass, linear and angular momentum transfer, and the speed of
real jets, with ~ 1000 times lower resolution than would be required without
SGS model. We apply the new SGS model to turbulent, magnetized star cluster
formation and show that jets and outflows (1) eject about 1/4 of their parent
molecular clump in high-speed jets, quickly reaching distances of more than a
parsec, (2) reduce the star formation rate by about a factor of two, and (3)
lead to the formation of ~ 1.5 times as many stars compared to the no-outflow
case. Most importantly, we find that jets and outflows reduce the average star
mass by a factor of ~ 3 and may thus be essential for understanding the
characteristic mass of the stellar initial mass function.
