FROM FILAMENTARY NETWORKS TO DENSE CORES IN MOLECULAR CLOUDS: TOWARD A NEW PARADIGM FOR STAR FORMATION
P. Andre (CEA Saclay, Laboratoire AIM - Service d'Astrophysique, Gif-sur-Yvette, France),
J. Di Francesco (National Research Council Canada, Herzberg Institute of Astrophysics, Canada),
S.-I. Inutsuka (Nagoya University, Japan),
R. Pudritz (McMaster University, Origins Institute, Canada),
D. Ward-Thompson (University of Central Lancashire, Jeremiah Horrocks Institute, UK),
J. Pineda (University of Manchester, Jodrell Bank Centre for Astrophysics, United Kingdom)
We review recent progress in our understanding of the physics controlling the earliest evolutionary
phases of star formation. Since PPV seven years ago, one area that has seen the most dramatic
advances has been the characterization of the link between star formation and the structure of the
cold interstellar medium (ISM). In particular, extensive studies of the nearest star-forming clouds of
our Galaxy with the Herschel Space Observatory have provided us with unprecedented images of the
initial and boundary conditions of the star formation process. The Herschel images reveal an intricate
network of filamentary structures in every interstellar cloud. The observed filaments share common
properties such as their central widths - but only the densest ones contain prestellar cores, the seeds
of future stars. Overall, the Herschel submillimeter data, as well as other observations from, e.g., near-
IR extinction studies, favor a scenario in which interstellar filaments and prestellar cores represent two
key steps in the star formation process: first supersonic turbulence stirs up the gas, giving rise to a
universal web-like structure in the ISM, then gravity takes over and controls the further fragmentation
of filaments into prestellar cores and ultimately protostars.
The new observational results connect remarkably well with nearly a decades worth of numerical
simulations and theory which have consistently shown that the ISM should be highly filamentary
on all scales and that star formation is intimately connected with self-gravitating filaments.
We thus attempt to synthesize a comprehensive physical picture that arises from the confrontation
of recent observations and simulations. We also emphasize how the apparent complexity
of cloud structure and star formation may be governed by relatively simple universal processes - from
filamentary clumps to galactic scales.
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