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

By P. Hennebelle, Romain Teyssier. 2007

154 citations recorded by the source corpus.

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 reveal 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 than ≃5, corresponding to higher 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 I 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 the case of weak perturbations is problematic. We discuss three possible mechanisms which could lead to the formation of binary systems, namely the presence of high amplitude fluctuations in the core initially, ambipolar diffusion and fragmentation during the second collapse.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/5a379c3b54a5296b043f8322b71be94623a7dc8e

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Citations in the corpus

Inefficient star formation through turbulence, magnetic fields and feedback (2015, background): “Simulation work by e.g., Price & Bate (2007) and Hennebelle & Teyssier (2008) suggested that magnetic fields can suppress fragmentation on small scales and hence influence the shape of the initial mass function of stars.”
H II REGIONS: WITNESSES TO MASSIVE STAR FORMATION (2010, background): “Banerjee & Pudritz (2006), Machida et al. (2005), Hennebelle & Teyssier (2008), Hennebelle & Fromang (2008) and Hennebelle & Ciardi (2009) furthermore show that the presence of magnetic fields can dramatically alter the shape and size of accretion disks and strongly suppress the formation of close…”
THE STAR FORMATION RATE OF TURBULENT MAGNETIZED CLOUDS: COMPARING THEORY, SIMULATIONS, AND OBSERVATIONS (2012, background): “…molecular clouds, magnetic fields seem to reduce fragmentation significantly (see Figure 4), thus potentially having a strong impact on the mass distribution of cores and stars (see also Price & Bate 2007; Hennebelle & Teyssier 2008; Bürzle et al. 2011; Peters et al. 2011; Hennebelle et al. 2011).”
RADIATION MAGNETOHYDRODYNAMIC SIMULATIONS OF PROTOSTELLAR COLLAPSE: NONIDEAL MAGNETOHYDRODYNAMIC EFFECTS AND EARLY FORMATION OF CIRCUMSTELLAR DISKS (2015, background): “…at least in the early phase of star formation and with the ideal magnetohydrodynamic (MHD) approximation, which is called the magnetic braking catastrophe (e.g., Mestel & Spitzer 1956; Allen et al. 2003; Mellon & Li 2008; Li et al. 2011, 2014b) or fragmentation crisis (Hennebelle & Teyssier 2008).”
THE INTERPLAY OF MAGNETIC FIELDS, FRAGMENTATION, AND IONIZATION FEEDBACK IN HIGH-MASS STAR FORMATION (2010, background): “…of magnetic pressure and tension forces providing additional support to counteract gravitational collapse (Ziegler 2005; Banerjee & Pudritz 2006; Price & Bate 2007; Hennebelle & Fromang 2008; Hennebelle & Teyssier 2008; Hennebelle & Ciardi 2009; Commerçon et al. 2010; Bürzle et al. 2010).”
Stellar Multiplicity (2013, background): “Numerical simulations including the effects of magnetic field and/or radiative feedback appear to match more closely observed multiplicity properties since these processes severely hinder fragmentation (e.g., Bate 2012, Hennebelle & Teyssier 2008).”
Dynamic star formation in the massive DR21 filament (2010, background): “Support from magnetic fields (Hennebelle & Teyssier 2008) and/or radiation (Krumholz 2006, Bate 2009) could drastically limit the level of fragmentation and channel the global infall to fewer, more massive protostars (Bontemps et al. 2010).”
THE FORMATION OF LOW-MASS BINARY STAR SYSTEMS VIA TURBULENT FRAGMENTATION (2010, background): “…using 3D ideal magnetohydrodynamics (MHD) find that the inclusion of magnetic fields suppresses disk fragmentation in the parameter space applicable to low-mass star formation (Price & Bate 2007; Hennebelle & Teyssier 2008), a result that is complementary to the role we find for radiative feedback.”
THE GENERATION OF STRONG MAGNETIC FIELDS DURING THE FORMATION OF THE FIRST STARS (2010, background): “We know from modeling galactic star-forming clouds that the presence of magnetic fields can reduce the level of fragmentation, and by doing so strongly influences the stellar mass spectrum (Hennebelle & Teyssier 2008).”
LIMITING ACCRETION ONTO MASSIVE STARS BY FRAGMENTATION-INDUCED STARVATION (2010, background): “This objection is, however, weakened by the fact that magnetic fields are able to reduce the level of fragmentation on scales of molecular clouds as a whole (Heitsch et al. 2001) as well as of collapsing cloud cores (Hennebelle & Fromang 2008; Hennebelle & Teyssier 2008).”
Fragmentation and mass segregation in the massive dense cores of Cygnus X (2009, methodology): “…towards high-mass fragments could be primordial if, for instance, another support such as the magnetic field could prevent from a high degree of fragmentation as it was already obtained using MHD numerical codes for the collapse of low-mass pre-stellar cores (Hennebelle & Teyssier 2008).”
Protostellar disk formation and transport of angular momentum during magnetized core collapse (2012, background): “The gravitational transport is nonetheless less efficient because of the symmetry of the disks, which is stabilized by the magnetic field, as emphasized in Hennebelle & Teyssier (2008); less symmetric disks would transport more momentum by means of gravitational torques.”
Physical Processes in the Interstellar Medium (2014, background): “It can alter how cores fragment (Price & Bate, 2007b, 2008; Hennebelle & Fromang, 2008; Hennebelle & Teyssier, 2008; Hennebelle et al., 2011; Peters et al., 2011), change the coupling between stellar feedback processes and their parent clouds (Nakamura & Li, 2007; Krumholz et al., 2007b), influence…”
The effect of magnetic fields on star cluster formation (2008, background): “Recent simulations by Price & Bate (2007) have shown that magnetic fields can have a dramatic effect on circumstellar disc formation and on fragmentation to form binary systems (these results have since beenconfirmed by Hennebelle & Teyssier 2008).”
Ambipolar diffusion in low-mass star formation - I. General comparison with the ideal magnetohydrodynamic case (2015, background): “…result of the very effective magnetic braking created by a strong pile-up of magnetic flux towards the centre of the collapsing system (Galli et al. 2006, Allen et al. 2003, Price & Bate 2007; Hennebelle & Teyssier 2008; Matsumoto & Tomisaka 2004; Hennebelle & Fromang 2008; Commerçon et al. 2010).”
Magnetic Fields of Nondegenerate Stars (2009, background): “Simulations further suggest that clouds with higher magnetic fi lds may form first cores (and presumably protostars as well) containing less angular momentum (e.g., Hennebelle & Fromang 2008) and are less prone to fragmentation (e.g., Machida et al. 2008b; Hennebelle & Teyssier 2008).”
RADIATION-HYDRODYNAMIC SIMULATIONS OF THE FORMATION OF ORION-LIKE STAR CLUSTERS. II. THE INITIAL MASS FUNCTION FROM WINDS, TURBULENCE, AND RADIATION (2012, background): “…in the litera- 11 ture about whether massive stars form from distinct massive protostellar cores (Padoan 1995; Padoan & Nordlund 2002; McKee & Tan 2002, 2003; Krumholz et al. 2007a; Hennebelle & Teyssier 2008; Hennebelle & Chabrier 2009), or whether all stars are born from cores with masses .”