On the structure of self-gravitating molecular clouds

To study the interaction of star-formation and turbulent molecular cloud st ructuring, we analyse numerical models and observations of self-gravitating clouds using the Delta -variance as statistical measure for structural cha racteristics. In the models we resolve the transition from purely hydrodyna mic turbulence to gravitational collapse associated with the formation and mass growth of protostellar cores. We compare models of driven and freely d ecaying turbulence with and without magnetic fields. Self-gravitating super sonic turbulence always produces a density structure that contains most pow er on the smallest scales provided by collapsed cores as soon as local coll apse sets in. This is in contrast to non-self-gravitating hydrodynamic turb ulence where the Delta -variance is dominated by large scale structures. To detect this effect in star-forming regions observations have to resolve th e high density contrast of protostellar cores with respect to their ambient molecular cloud. Using the 3 mm continuum map of a star-forming cluster in Serpens we show that the dust emission traces the full density evolution. On the contrary, the density range accessible by molecular line observation s is insufficient for this analysis. Only dust emission and dust extinction observations are able to to determine the structural parameters of star-fo rming clouds following the density evolution during the gravitational colla pse.