Orion A integral shaped filament image

In addition, the spatial distribution of the cores indicates periodic grouping of the cores into groups of ~30000AU in size, separated by ~50000AU. The groups coincide with dust column density peaks detected by Herschel. These results show hierarchical, two-mode fragmentation in which the maternal filament periodically fragments into groups of dense cores.

Critically, our results indicate that the fragmentation models for lower line-mass filaments (~16M_{sun}_/pc) fail to capture the observed properties of the ISF. We also find that the protostars identified with Spitzer and Herschel in the ISF are grouped at separations below ~17000AU. In contrast, young stars with disks do not show significant grouping.

This suggests that the grouping of dense cores is partially retained over the protostar lifetime, but not over the lifetime of stars with disks. This is in agreement with a scenario where protostars are ejected from the maternal filament by the slingshot mechanism, a model recently proposed for the ISF. The separation distributions of the dense cores and protostars may also provide an evolutionary tracer of filament fragmentation.