Emmy Noether Application

has formed.
Recent direct detections of the magnetic field configuration in the protostellar accretion disc
FU Orionis confirm the idea that magnetic fields are wound up and pinched in such a
disc (Donati et al., 2005). The lack of a strong collimated outflow from this object could
be due to a strong magnetic braking effect which slows down the disc plasma. We proposed
a follow-up observation of this protostar (Jean-Francois Donati being the principal investigator)
with the ESPaDOnS instrument on the Canada-France-Hawaii Telescope (CFHT). Within
the proposed 15 day observational period we hope to get clear Zeeman signatures which will
reveal in unprecedented detail the magnetic field structure in this object.
We also studied the influence of magnetic fields during the collapse of massive molecular
cores (Banerjee & Pudritz, 2007). For a similar setup than described above but a higher
core mass (M ∼ 170M⊙) we could show that outflows and jets can be launched by the
same mechanism than in low-mass case (see Figure 7). Even if these outflows are not long
lived, i.e. do not propagate far into the cloud, this has particular interesting implications for
massive star formation: These outflows and jets will punch cavities into the infalling envelope.
It is known that radiation, then emitted from the young massive star, will choose the way of
least resistance and escape through the outflow carved cavities (Krumholz et al., 2005b).
Krumholz et al. showed that these radiation funnels lower the radiation pressure exerted
on the gas next to the funnels and the disc. Therefore, upper mass limits for massive stars
derived from radiation pressure (e.g., Wolfire & Cassinelli, 1987) will be weakened or even
removed by this mechanism.
Another implication due to outflows and magnetic fields comes from the extraction of angular
momentum. Disc winds extract angular momentum while physically removing gas with nonvanishing
specific angular momentum from the disc. Magnetic fields exert torques on the
disc if their field lines connect fast and slowly circulating gas at the same time (e.g., Pudritz,
2003). Typically, the disc fields connect to slower rotating gas further out (like in the case
where the magnetic field is dragged inwards by the infalling gas) and the resulting torques
spin down the disc. This in turn will increase accretion as gas with high specific angular
momentum at the edge of the disc can settle deeper into the gravitational potential. By
removing angular momentum from the disc magnetic fields and outflows can actually help to
assemble massive stars quickly. In Banerjee & Pudritz (2006) we showed that the magnetic
torque and the angular momentum loss by the disc wind are comparable to the angular
momentum gain by the infalling gas.
In Section 3.1 we discuss how we will extend and improve the work we did so far on studying
outflows and jets. In particular, with the prospective sink particle approach we will be able to
study these outflows for much longer dynamical time and more rational periods.
Driving of Supersonic Turbulence
Massive stars are formed in an environment of supersonic turbulence (e.g., Elmegreen &
Scalo, 2004; Mac Low & Klessen, 2004; Ballesteros-Paredes et al., 2007). It is known that
supersonic turbulence decays quickly and has to be continuously driven to maintain (e.g.,
Stone et al., 1998; Mac Low et al., 1998; Padoan et al., 1999). So far we do not have a
conclusive mechanism which could serve as a driving source for the observed supersonic
turbulence in molecular clouds. Many proposals have been made among are such which
inject energy into the gas from inside the cloud. Norman & Silk (1980) firstly proposed
that jets from YSOs could sufficiently stir up their environment. This is an interesting idea
in the context of turbulence regulated star formation. Supersonic turbulence can, on small
scales, prevent star formation because here it supports the gas against gravity. On large
scales, it can compress enough gas in clumps and cores which can become supercritical
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