25 janvier 2019
Recent Herschel observations have revealed that most of the stars in our Galaxy are formed inside filaments. Using single-dish and ALMA molecular observations, we have investigated the internal structure and dynamics of filaments along their entire mass spectrum, from the lowest mass filaments in Taurus to the massive Integral Shape Filament in Orion. In all cases, the analysis of different molecular line tracers indicates a high level of internal organization in which apparently single filaments are actually collections of small-scale fibers. In both low- and high-mass filaments, fibers are characterized by presenting transonic internal motions respect to their local sound speed and a mass per-unit-length close to hydrostatic equilibrium. Conversely, the fiber dimensions (width and length) appear to be self-regulated depending on their intrinsic gas density of their local environment. Combining observations in different star-forming regions, we identify a systematic increase of the surface density of fibers as a function of the total mass per-unit-length in filamentary clouds. Based on this empirical correlation, we propose a unified star-formation scenario where the observed differences between low- and high-mass clouds, and the origin of clusters, emerge naturally from the initial concentration of fibers.