Protostellar Turbulence Driven by Collimated Outflows

By F. Nakamura, Zhi-Yun Li. 2007

214 citations recorded by the source corpus.

We investigate the global properties of the outflow-driven protostellar turbulence through 3D MHD simulations. The simulations show that the turbulence in regions of active cluster formation is quickly transformed by the forming stars through protostellar outflows, and that strongly influences and perhaps controls protostellar turbulence cluster formation. We find that collimated outflows are more efficient in driving turbulence than spherical outflows that carry the same amounts of momentum. This is because collimated outflows can propagate farther away from their sources, effectively increasing the turbulence driving length; turbulence driven on a larger scale decays more slowly. Gravity plays an important role in shaping the turbulence, generating infall motions that balance the outward motions driven by outflows. The resulting quasi-equilibrium state is maintained through a slow rate of star formation, with a fraction of the total mass converted into stars per free-fall time as low as a few percent. Magnetic fields are dynamically important even in magnetically supercritical clumps, provided that their initial strengths are not far below the critical value for static cloud support. They contain an energy comparable to the turbulent energy and can significantly reduce the rate of star formation. The mass-weighted probability distribution function (PDF) of the volume density of the protostellar turbulence is often, although not always, approximately lognormal. The PDFs of the column density deviate more strongly from lognormal distributions. There is a prominent break in the power spectrum, which may provide a way to distinguish it from other types of turbulence.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/9f49867b962562c4b858c5e1022c56e685fdd479

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Citations in the corpus

THE DISRUPTION OF GIANT MOLECULAR CLOUDS BY RADIATION PRESSURE & THE EFFICIENCY OF STAR FORMATION IN GALAXIES (2009, methodology): “We variedǫjet over the range 0.1− 0.3 giving an effective velocity in the range 30− 90km s−1, bracketing that found by, e.g., Matzner & McKee (2000) and Nakamura & Li (2007).”
On the fraction of star formation occurring in bound stellar clusters (2012, methodology): “The typical protostellar outflow velocities of ∼0.5 km s−1 in the numerical work of Nakamura & Li (2007) are consistent with this picture, and for protoclusters with radii of 1 pc they imply crossing times of 2 Myr.”
On the Rapid Collapse and Evolution of Molecular Clouds (2007, background): “Li & Nakamura (2006) and Nakamura & Li (2007) took a different approach.”
A UNIVERSAL, LOCAL STAR FORMATION LAW IN GALACTIC CLOUDS, NEARBY GALAXIES, HIGH-REDSHIFT DISKS, AND STARBURSTS (2011, unknown): “In regions lacking massive stars the turbulence can be driven by mechanisms such as protostellar outflows (Li & Nakamura 2006; Nakamura & Li 2007; Matzner 2007), while in regions containing massive stars it is driven by the radiation pressure (Krumholz & Matzner 2009; Murray et al. 2010) or…”
Before the first supernova: combined effects of H II regions and winds on molecular clouds (2014, unknown): “Li & Nakamura (2006); Nakamura & Li (2007) and Matzner (2007) all concluded that outflows can be efficient drivers of turbulence.”
OUTFLOW FEEDBACK REGULATED MASSIVE STAR FORMATION IN PARSEC-SCALE CLUSTER-FORMING CLUMPS (2009, methodology): “In this paper, we will improve on the previous outflow feedback simulations of Nakamura & Li (2007) by including sink particles, making the outflow injection more continuous, and dramatically increasing the numerical resolution.”
THE LONG-TERM EVOLUTION OF THE GALACTIC DISK TRACED BY DISSOLVING STAR CLUSTERS (2010, background): “…about whether star cluster formation occurs in a single crossing time (Elmegreen 2000; Hartmann et al. 2001; Elmegreen 2007; Pflamm-Altenburg & Kroupa 2007) or over 3 − 4 crossing times (Tan et al. 2006; Huff & Stahler 2006; Krumholz & Tan 2007; Jeffries 2007; Nakamura & Li 2007; Matzner 2007).”
RADIATION-HYDRODYNAMIC SIMULATIONS OF THE FORMATION OF ORION-LIKE STAR CLUSTERS. II. THE INITIAL MASS FUNCTION FROM WINDS, TURBULENCE, AND RADIATION (2012, background): “This result at first appears to contradict those of previous studies, including Li & Nakamura (2006), Nakamura & Li (2007), Matzner (2007), Wang et al. (2010), and Cunningham et al. (2011), all of whom find that outflow feedback is important.”
Global hierarchical collapse in molecular clouds. Towards a comprehensive scenario (2019, background): “2011), and by numerical simulations of the effect of feedback from stellar outflows on clump-sized (∼ 1 pc) structures (e.g., Nakamura & Li 2005, 2007; Li & Nakamura 2006; Carroll et al. 2009, see also the reviews by VázquezSemadeni 2011 and Krumholz et al. 2014).”
DIRECT NUMERICAL SIMULATION OF RADIATION PRESSURE-DRIVEN TURBULENCE AND WINDS IN STAR CLUSTERS AND GALACTIC DISKS (2012, background): “Simulations of mechanical feedback from both protostellar outflows (Li & Nakamura 2006; Nakamura & Li 2007; Wang et al. 2010) and photoionization-driven “champagne” flows from molecular clouds (Gendelev & Krumholz 2012) show that strong, ordered magnetic fields can significantly enhance the effects…”
Magnetically Regulated Star Formation in Three Dimensions: The Case of the Taurus Molecular Cloud Complex (2008, methodology): “This trend is the opposite of what we found in the case of cluster formation in dense clumps that are globally magnetically supercritical (Nakamura & Li 2007): for a given total outflow momentum, more spherical outflows tend to drive turbulence on a smaller scale that dissipates more quickly,…”
Stellar, brown dwarf and multiple star properties from a radiation hydrodynamical simulation of star cluster formation (2011, background): “…in globally unbound molecular clouds (Clark & Bonnell 2004; Clark et al. 2005), or that magnetic support (Price & Bate 2008, 2009), kinetic feedback (Matzner & McKee 2000; Krumholz, Matzner & McKee 2006; Nakamura & Li 2007) or a combination (e.g. Wang et al. 2010) reduces the star formation rate.”
What controls star formation in the central 500 pc of the Galaxy (2013, background): “In Longmore et al. (2013a), we show that these relations do indeed over-predict the measurd star 1 Except for the mass loss due to protostellar outflows (e.g. Matzner & McKee 2000; Nakamura & Li 2007). formation rate by factors of 10 to 100.”
Turbulent molecular clouds (2012, background): “The inclusion of the feedback from protostellar jets has been considered by Nakamura & Li (2007) and Wang et al. (2010).”
Global Models for the Evolution of Embedded, Accreting Protostellar Disks (2007, result): “Matzner (2007) and Nakamura & Li (2007) have shown that a shallower index is expected when turbulence is driven by protostellar outflows, however, and our chosen power spectrum is consistent with the line width-size relation for massive cores (e.g., Caselli & Myers 1995; Plume et al. 1997).”