The Generation of Strong Magnetic Fields During the Formation of the First Stars

Sur, Sharanya; Schleicher, Dominik R. G.; Banerjee, Rinti; Federrath, Christoph; Klessen, Ralf S.

doi:10.1088/2041-8205/721/2/l134

Cited by 198 publications

(218 citation statements)

References 45 publications

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“…By contrast, stellar feedback or gravitational infall would produce a shock, i.e., a discontinuity, but we see a rather smooth gradient, which is most likely associated with shear (Kruijssen et al 2016, in preparation). Such large-scale systematic motions must be subtracted in order to isolate the turbulent motions on scales smaller or equal to the size of the cloud (e.g., Burkert & Bodenheimer 2000;Sur et al 2010;Federrath et al 2011b). In order to isolate the turbulent motions, we fit the gradient with a plane, shown in the middle panel, and then subtract it from the original velocity map (shown in the top right-hand panel of Figure 4).…”

Section: Velocity Mapsmentioning

confidence: 99%

The Link Between Turbulence, Magnetic Fields, Filaments, and Star Formation in the Central Molecular Zone Cloud G0.253+0.016

Federrath

Rathborne

Longmore

et al. 2016

ApJ

176

235

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Star formation is primarily controlled by the interplay between gravity, turbulence, and magnetic fields. However, the turbulence and magnetic fields in molecular clouds near the Galactic center may differ substantially compared to spiral-arm clouds. Here we determine the physical parameters of the central molecular zone (CMZ) cloud G0.253 +0.016, its turbulence, magnetic field, and filamentary structure. Using column density maps based on dust

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Section: Velocity Mapsmentioning

confidence: 99%

The Link Between Turbulence, Magnetic Fields, Filaments, and Star Formation in the Central Molecular Zone Cloud G0.253+0.016

Federrath

Rathborne

Longmore

et al. 2016

ApJ

176

235

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“…5. In a companion paper (Sur et al 2010), we present numerical simulations confirming the importance of dynamo amplification during gravitational collapse.…”

Section: Introductionmentioning

confidence: 82%

Small-scale dynamo action during the formation of the first stars and galaxies

Schleicher

Banerjee

Sur

et al. 2010

A&A

Self Cite

188

176

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We explore the amplification of magnetic seeds during the formation of the first stars and galaxies. During gravitational collapse, turbulence is created from accretion shocks, which may act to amplify weak magnetic fields in the protostellar cloud. Numerical simulations showed that such turbulence is sub-sonic in the first star-forming minihalos, and highly supersonic in the first galaxies with virial temperatures larger than 10 4 K. We investigate the magnetic field amplification during the collapse both for Kolmogorov and Burgers-type turbulence with a semi-analytic model that incorporates the effects of gravitational compression and small-scale dynamo amplification. We find that the magnetic field may be substantially amplified before the formation of a disk. On scales of 1/10 of the Jeans length, saturation occurs after ∼10 8 yr. Although the saturation behaviour of the small-scale dynamo is still somewhat uncertain, we expect a saturation field strength of the order ∼10 −7 n 0.5 G in the first star-forming halos, with n the number density in cgs units. In the first galaxies with higher turbulent velocities, the magnetic field strength may be increased by an order of magnitude, and saturation may occur after 10 6 −10 7 yr. In the Kolmogorov case, the magnetic field strength on the integral scale (i.e. the scale with most magnetic power) is higher due to the characteristic power-law indices, but the difference is less than a factor of 2 in the saturated phase. Our results thus indicate that the precise scaling of the turbulent velocity with length scale is of minor importance. They further imply that magnetic fields will be significantly enhanced before the formation of a protostellar disk, where they may change the fragmentation properties of the gas and the accretion rate.

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“…The final stellar masses are determined by the balance of the above competing effects, which would also be affected by stellar radiative feedback (e.g., Stacy et al 2012;Susa 2013). Moreover, recent magnetohydrodynamic simulations show that even a small amount of turbulence can amplify magnetic fields by a dynamo mechanism (Sur et al 2010;Federrath et al 2011;Sur et al 2012;Turk et al 2012). The existence of magnetic fields would increase angular momentum transfer in the disc via magnetic braking, preventing disc fragmentation as well as enhancing accretion rates on to the protostars (e.g., Machida & Doi 2013).…”

Section: Uncertainty In Mass Estimationmentioning

confidence: 99%

Primordial star formation under the influence of far ultraviolet radiation: 1540 cosmological haloes and the stellar mass distribution

Hirano

Hosokawa

Yoshida

et al. 2015

Monthly Notices of the Royal Astronomical Society

318

313

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We perform a large set of cosmological simulations of early structure formation and follow the formation and evolution of 1540 star-forming gas clouds to derive the mass distribution of primordial stars. The star formation in our cosmological simulations is characterized by two distinct populations, the so-called Population III.1 stars and primordial stars formed under the influence of far-ultraviolet (FUV) radiation (Population III.2 D stars). In this work, we determine the stellar masses by using the dependences on the physical properties of star-forming cloud and/or the external photodissociating intensity from nearby primordial stars, which are derived from the results of 2D radiation hydrodynamic simulations of protostellar feedback. The characteristic mass of the Pop III stars is found to be a few hundred solar masses at z ∼ 25, and it gradually shifts to lower masses with decreasing redshift. At high redshifts z > 20, about half of the star-forming gas clouds are exposed to intense FUV radiation and thus give birth to massive Pop III.2 D stars. However, the local FUV radiation by nearby Pop III stars becomes weaker at lower redshifts, when typical Pop III stars have smaller masses and the mean physical separation between the stars becomes large owing to cosmic expansion. Therefore, at z < 20, a large fraction of the primordial gas clouds host Pop III.1 stars. At z 15, the Pop III.1 stars are formed in relatively cool gas clouds due to efficient radiative cooling by H 2 and HD molecules; such stars have masses of a few ×10 M ⊙ . Since the stellar evolution and the final fate are determined by the stellar mass, Pop III stars formed at different epochs play different roles in the early Universe.

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The Generation of Strong Magnetic Fields During the Formation of the First Stars

Cited by 198 publications

References 45 publications

The Link Between Turbulence, Magnetic Fields, Filaments, and Star Formation in the Central Molecular Zone Cloud G0.253+0.016

The Link Between Turbulence, Magnetic Fields, Filaments, and Star Formation in the Central Molecular Zone Cloud G0.253+0.016

Small-scale dynamo action during the formation of the first stars and galaxies

Primordial star formation under the influence of far ultraviolet radiation: 1540 cosmological haloes and the stellar mass distribution

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