Filamentary structure of star-forming complexes
  The nearest young stellar groups are associated with "hubs" of column density
exceeding 10^22 cm^-2, according to recent observations. These hubs radiate
multiple "filaments" of parsec length, having lower column density and fewer
stars. Systems with many filaments tend to have parallel filaments with similar
spacing. Such "hub-filament structure" is associated with all of the nine young
stellar groups within 300 pc, forming low-mass stars. Similar properties are
seen in infrared dark clouds forming more massive stars. In a new model, an
initial clump in a uniform medium is compressed into a self-gravitating,
modulated layer. The outer layer resembles the modulated equilibrium of
Schmid-Burgk (1967) with nearly parallel filaments. The filaments converge onto
the compressed clump, which collapses to form stars with high efficiency. The
initial medium and condensations have densities similar to those in nearby
star-forming clouds and clumps. The predicted structures resemble observed
hub-filament systems in their size, shape, and column density, and in the
appearance of their filaments. These results suggest that hub-filament
structure associated with young stellar groups may arise from compression of
clumpy gas in molecular clouds.
