  We present simulations of collapsing filaments studying the impact of
turbulence and magnetic field morphologies on their evolution and star
formation properties. We vary the mass per unit length of the filaments as well
as the orientation of the magnetic field with respect to the major axis. We
find that the filaments, which have no or a perpendicular magnetic field,
typically reveal a smaller width than the universal width of 0.1 pc proposed by
e.g. Arzoumanian et al. 2011. We show that this also holds in the presence of
supersonic turbulence and that accretion driven turbulence is too weak to
stabilize the filaments along their radial direction. On the other hand, we
find that a magnetic field that is parallel to the major axis can stabilize the
filament against radial collapse resulting in widths of 0.1 pc. Furthermore,
depending on the filament mass and magnetic field configuration, gravitational
collapse and fragmentation in filaments occurs either in an edge-on way,
uniformly distributed across the entire length, or in a mixed way. In the
presence of initially moderate density perturbations, a centralized collapse
towards a common gravitational centre occurs. Our simulations can thus
reproduce different modes of fragmentation observed recently in star forming
filaments. Moreover, we find that turbulent motions influence the distance
between individual fragments along the filament, which does not always match
the results of a Jeans analysis.
