The Turbulent Shock Origin of Proto-Stellar Cores

By P. Padoan, M. Juvela, A. Goodman, Åke Nordlund. 2000

207 citations recorded by the source corpus.

The fragmentation of molecular clouds (MC) into proto-stellar cores is a central aspect of the process of star formation. Because of the turbulent nature of supersonic motions in MCs, it has been suggested that dense structures such as filaments and clumps are formed by shocks in a turbulent flow. In this work we present strong evidence in favor of the turbulent origin of the fragmentation of MCs. The most generic result of turbulent fragmentation is that dense postshock gas traces a gas component with a smaller velocity dispersion than lower density gas, since shocks correspond to regions of converging flows, where the kinetic energy of the turbulent motion is dissipated. Using synthetic maps of spectra of molecular transitions, computed from the results of numerical simulations of supersonic turbulence, we show that the dependence of velocity dispersion on gas density generates an observable relation between the rms velocity centroid and the integrated intensity (column density), σ(V0)-I, which is indeed found in the observational data. The comparison between the theoretical model (maps of synthetic 13CO spectra) with 13CO maps from the Perseus, Rosette, and Taurus MC complexes shows excellent agreement in the σ(V0)-I relation. The σ(V0)-I relation of different observational maps with the same total rms velocity are remarkably similar, which is a strong indication of their origin from a very general property of the fluid equations, such as the turbulent fragmentation process.

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Citations in the corpus

The Stellar Initial Mass Function from Turbulent Fragmentation (2000, methodology): “The main results of this work are as follows: (1) the power-law stellar IMF at masses larger than 1–2 M is the result of the near self-similar nature of inertial range supersonic turbulence; (2) the low-mass rollover and cutoff of the IMF is caused by the combined effects of the thermal support of t”
SIMBA survey of southern high-mass star forming regions. I. Physical parameters of the 1.2-mm/IRAS sources (2004, background): “The clumpy structure could be explained if the cores are formed by turbulent shocks (Padoan et al. 2001).”
Cores, filaments, and bundles: hierarchical core formation in the L1495/B213 Taurus region (2013, background): “…mechanisms have been proposed over the years, ranging from quasi-static contraction mediated by ambipolar-diffusion (Shu et al. 1987; Mouschovias & Ciolek 1999) to gravo-turbulent fragmentation driven by supersonic motions (Padoan et al. 2001; Klessen et al. 2005; Vázquez-Semadeni et al. 2005).”
Interstellar Turbulence I: Observations and Processes (2004, methodology): “Padoan et al. (2001c) measured the line-of-sight thickness of the LMC using the transition length where the slope of the spectral correlation function versus separation goes from steep on small scales to shallow on large scales.”
Galactic Stellar and Substellar Initial Mass Function (2003, unknown): “10 µG) (Crutcher & Troland 2000, Padoan & Nordlund 1999, Padoan et al. 2001a,b, 2001b Bourke et al. 2001).”
Dense core formation by fragmentation of velocity-coherent filaments in L1517 (2011, background): “…these models, the cores are shock-compressed structures formed at the stagnation point between two convergent flows, and as a result, they are expected to be surrounded (even confined) by turbulent layers of cloud gas (e.g., Padoan et al. 2001; Ballesteros-Paredes et al. 2003; Klessen et al. 2005).”
Cooling, Gravity, and Geometry: Flow-driven Massive Core Formation (2007, methodology): “Since we are interested in global gravitational effects, we cannot use the periodic boundary conditions of earlier turbulent fragmentation studies (e.g. Klessen et al. 2000; Heitsch et al. 2001; Padoan et al. 2001; Gammie et al. 2003; Vázquez-Semadeni et al. 2005).”
The physics of star formation (2003, background): “…shocks are still unavoidably produced by motions along the field lines, and these shocks compress the gas into structures that can be sheetlike or filamentary or clumpy (Ostriker et al 1999, 2001; Vazquez-Semadeni et al 2000; Klessen et al 2000; Padoan et al 2001; Gammie et al 2003; Mac Low 2003).”
Cold Dark Clouds: The Initial Conditions for Star Formation (2007, background): “Models of supersonic turbulence show that the highest density gas moves slower than the low density material, as it arises from the convergence of flows (e.g., Padoan et al. 2001), and this velocity segregation seems to be present in clouds.”
Star Formation from Galaxies to Globules (2001, background): “…Kim, & Staveley-Smith 2001), and galactic nuclei (Elmegreen, Elmegreen, & Eberwein 2002b), show no characteristic scale between the size of the beam and the size of the map, except possibly for the line-of-sight galaxy thickness if that is resolved (Elmegreen et al. 2001; Padoan et al. 2001b).”
Physical Processes in the Interstellar Medium (2014, background): “More recent discussions on the topic of ISM dynamics can be found in Hennebelle & Falgarone (2012) as well as in Protostars and Planets VI, in particular in the chapters by Padoan et al. (2014) or Dobbs et al. (2014).”
Global hierarchical collapse in molecular clouds. Towards a comprehensive scenario (2019, background): “While in GT filaments are assumed to be the result of shocks, with no need for developing a longitudinal flow (e.g., Padoan et al. 2001), in GHC the filaments constitute the very accretion flow from large to small scales, akin to rivers carrying the material down the gravitational potential from…”
Turbulent molecular clouds (2012, result): “This scenario is somehow similar to that proposed by Padoan et al. (2001) which show that, in their simulations, the filaments correspond to low velocity regions and are often found at the intersection between shocked layers.”
A census of dense cores in the Aquila cloud complex: SPIRE/PACS observations from the Herschel Gould Belt survey (2015, background): “…filaments result from planar intersecting shock waves due to supersonic interstellar turbulence (e.g. Pudritz & Kevlahan 2013), and that the filament width corresponds to the sonic scale below which the turbulence becomes subsonic in diffuse, non-star-forming molecular gas (cf. Padoan et al. 2001).”
Rapid Formation of Molecular Clouds and Stars in the Solar Neighborhood (2001, methodology): “…limitations placed on cloud lifetimes by stellar populations essentially ensure that the evolution from dispersed molecular gas to protostellar cores is dynamic rather than quasi-static (Ballesteros-Paredes, VázquezSemadeni & Scalo 1999 = BVS; Klessen, Heitsch, & Mac Low 2000; Padoan et al. 2001).”
The “Mysterious” Origin of Brown Dwarfs (2002, background): “In the present work we investigate the possibility that BDs are the direct consequence of turbulent fragmentation (Padoan & Nordlund 1999, 2002; Padoan et al. 2001; Nordlund & Padoan 2002), in the sense that they are assembled by the turbulent flow as gravitationally unstable objects.”
ERRATUM: “THE LUMINOSITY AND MASS FUNCTIONS OF LOW-MASS STARS IN THE GALACTIC DISK. II. THE FIELD” (2010, AJ, 139, 2679) (2010, background): “Turbulent fragmentation occurs when supersonic shocks compress the molecular gas (Larson 1981; Padoan et al. 2001).”
THE STAR FORMATION RATE OF SUPERSONIC MAGNETOHYDRODYNAMIC TURBULENCE (2009, background): “The turbulence is responsible for much of the complex and filamentary density structure observed in molecular clouds, and prestellar cores are likely assembled as the densest regions in this turbulent fragmentation process (Padoan et al. 2001).”