Protostars and Planets VI, Heidelberg, July 15-20, 2013
Cores, Filaments, and Bundles: Hierarchical core formation in the B213 filament in Taurus
Hacar, Alvaro (Institut for Astrophysics - Univ. Vienna)
Tafalla, Mario (Observatorio Astronomico Nacional)
Kauffmann, Jens (Caltech)
Kovacs, Attila (University of Minnesota)
Characterizing the dense core formation in filaments is a critical step for our understanding of the star formation process within molecular clouds. Using different molecular tracers to study the gas kinematics at different scales and density regimes, we have investigated the dense core formation in the B213/L1495 filament in Taurus, one of the most prominent structures identified in nearby clouds (see Hacar et al 2013, A&A, 554, A55). Our analysis of its internal kinematics demonstrates that this filament is actually a bundle of 35 velocity-coherent filaments, typically with lengths of ∼ 0.5 pc and oscillatory-like and sonic velocity field, each of them exhibiting linear masses close to the expected mass for a filament in hydrostatic equilibrium. Among them, only a small fraction of these filaments (∼1/4) are ”fertile” and efficiently fragment forming all the cores identified within this region, while most of them (∼3/4) do not form cores and remain ”sterile”. Our observations then suggest that core formation in Taurus occurs in two steps. First, 0.5 pc-long velocity-coherent filaments condense out of the cloud gas, probably as a result of the turbulent cascade. After that, the dense cores condense quasi-statically in only those ”fertile” filaments that have accumulated enough mass to became gravitational unstable, inheriting their kinematic properties. The formation of these velocity-coherent filaments appears therefore as a critical step on the star formation process being the first subsonic structures formed out of the turbulent regime that dominates the cloud dynamics at large scales.
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