Magnetic Fields from Filaments to Cores
  How important is the magnetic (B-) field when compared to gravity and
turbulence in the star-formation process? Does its importance depend on scale
and location? We summarize submm dust polarization observations towards the
large filamentary infrared dark cloud G34 and towards a dense core in the
high-mass star-forming region W51. We detect B-field orientations that are
either perpendicular or parallel to the G34 filament axis. These B-field
orientations further correlate with local velocity gradients. Towards three
cores in G34 we find a varying importance between B-field, gravity, and
turbulence that seems to dictate varying types of fragmentation. At highest
resolution towards the gravity-dominated collapsing core W51 e2 we resolve new
B-field features, such as converging B-field lines and possibly magnetic
channels.
