Early stages of star formation

André, P.; Hennebelle, P.; Peretto, N.

doi:10.1007/978-1-4020-6935-2_6

Cited by 2 publications

(2 citation statements)

References 33 publications

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“…In order to test each of these scenarios, high resolution observations would be necessary. In this respect, ALMA will certainly be a very powerful tool as demonstrated by the synthetic observations performed by André et al (2007) using the present calculations.…”

Section: Fragmentation During the Second Collapsementioning

confidence: 69%

Magnetic processes in a collapsing dense core. II Fragmentation. Is there a fragmentation crisis ?

Hennebelle,

Teyssier

2007

Preprint

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Context. A large fraction of stars are found in binary systems. It is therefore important for our understanding of the star formation process, to investigate the fragmentation of dense molecular cores. Aims. We study the influence of the magnetic field, ideally coupled to the gas, on the fragmentation in multiple systems of collapsing cores. Methods. We present high resolution numerical simulations performed with the RAMSES MHD code starting with a uniform sphere in solid body rotation and a uniform magnetic field parallel to the rotation axis. We pay particular attention to the strength of the magnetic field and interpret the results using the analysis presented in a companion paper. Results. The results depend much on the amplitude, A, of the perturbations seeded initially. For a low amplitude, A = 0.1, we find that for values of the mass-to-flux over critical mass-to-flux ratio, µ, as high as µ = 20, the centrifugally supported disk which fragments in the hydrodynamical case, is stabilized and remains axisymmetric. Detailed investigations reveals that this is due to the rapid growth of the toroidal magnetic field induced by the differential motions within the disk. For values of µ smaller ≃ 5, corresponding to larger magnetic intensities, there is no centrifugally supported disk because of magnetic braking. When the amplitude of the perturbation is equal to A = 0.5, each initial peak develops independently and the core fragments for a large range of µ. Only for values of µ close to 1 is the magnetic field able to prevent the fragmentation. Conclusions. Since a large fraction of stars are binaries, the results of low magnetic intensities preventing the fragmentation in case of weak perturbations, is problematic. We discuss three possible mechanisms which could lead to the formation of binary systems namely the presence of large amplitude fluctuations in the core initially, the ambipolar diffusion and the fragmentation during the second collapse.

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Section: Fragmentation During the Second Collapsementioning

confidence: 69%

Magnetic processes in a collapsing dense core. II Fragmentation. Is there a fragmentation crisis ?

Hennebelle,

Teyssier

2007

Preprint

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“…The spitzer experiment has begun producing higher spatial resolution mid-infrared maps (Churchwell et al 2004) and revealed the fine structure of the star forming regions. The advent of major new facilities in the coming years should yield several breakthroughs in this field (André et al 2008). A higher resolution observation in future is assuredly expected to reveal hidden, small structures, as well as sub-stellar objects with very small mass (Atacama Large Millimeter Array, alma, becoming partly available in 2011, fully operational at 2013).…”

Section: Introductionmentioning

confidence: 99%

Investigating thermal evolution of the self-gravitating one dimensional molecular cloud by smoothed particle hydrodynamics

Nejad-Asghar

Molteni

2008

Astrophys Space Sci

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The heating of the ion-neutral (or ambipolar) diffusion may affect the thermal phases of the molecular clouds. We present an investigation on the effect of this heating mechanism in the thermal instability of the molecular clouds. A weakly ionized one dimensional slab geometry, which is allowed for self-gravity and ambipolar diffusion, is chosen to study its thermal phases. We use the thermodynamic evolution of the slab to obtain the regions where slab cloud becomes thermally unstable. We investigate this evolution using the model of ambipolar diffusion with two-fluid smoothed particle hydrodynamics, as outlined by Hosking & Whitworth. Firstly, some parts of the technique are improved to test the pioneer works on behavior of the ambipolar diffusion in an isothermal self-gravitating slab. Afterwards, the improved two-fluid technique is used for thermal evolution of the slab. The results show that the thermal instability may persist inhomogeneities with a large density contrast at the intermediate parts of the cloud. We suggest that this feature may be responsible for the planet formation in the intermediate regions of a collapsing molecular cloud and/or may also be relevant to the formation of star forming dense cores in the clumps.

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Early stages of star formation

Cited by 2 publications

References 33 publications

Magnetic processes in a collapsing dense core. II Fragmentation. Is there a fragmentation crisis ?

Magnetic processes in a collapsing dense core. II Fragmentation. Is there a fragmentation crisis ?

Investigating thermal evolution of the self-gravitating one dimensional molecular cloud by smoothed particle hydrodynamics

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