Importance of the Initial Conditions for Star Formation - I. Cloud Evolution and Morphology

By P. Girichidis, Christoph Federrath, Robi Banerjee, Ralf Klessen. 2010

147 citations recorded by the source corpus.

We present a detailed parameter study of collapsing turbulent cloud cores, varying the initial density profile and the initial turbulent velocity field. We systematically investigate the influence of different initial conditions on the star formation process, mainly focusing on the fragmentation, the number of formed stars and the resulting mass distributions. Our study compares four different density profiles (uniform, Bonnor-Ebert type, ρ ∝ r ―1.5 and ρ ∝ r ―2 ), combined with six different supersonic turbulent velocity fields (compressive, mixed and solenoidal, initialized with two different random seeds each) in three-dimensional simulations using the adaptive-mesh refinement, hydrodynamics code FLASH. The simulations show that density profiles with flat cores produce hundreds of low-mass stars, either distributed throughout the entire cloud or found in subclusters, depending on the initial turbulence. Concentrated density profiles always lead to the formation of one high-mass star in the centre of the cloud and, if at all, low-mass stars surrounding the central one. In uniform and Bonnor-Ebert type density distributions, compressive initial turbulence leads to local collapse about 25 per cent earlier than solenoidal turbulence. However, central collapse in the steep power-law profiles is too fast for the turbulence to have any significant influence. We conclude that (i) the initial density profile and turbulence mainly determine the cloud evolution and the formation of clusters, (ii) the initial mass function (IMF) is not universal for all setups and (iii) that massive stars are much less likely to form in flat density distributions. The IMFs obtained in the uniform and Bonnor-Ebert type density profiles are more consistent with the observed IMF, but shifted to lower masses.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/9cc0171fa625ef022c74e872a289f18decd4aee9

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Citations in the corpus

THE STAR FORMATION RATE OF TURBULENT MAGNETIZED CLOUDS: COMPARING THEORY, SIMULATIONS, AND OBSERVATIONS (2012, methodology): “The other extreme would be to initialize a cloud in isolation as done in related studies (e.g., Bate et al. 2003; Clark et al. 2005; Krumholz et al. 2007; Price & Bate 2008, 2009; Smith et al. 2008; Federrath et al. 2010a; Walch et al. 2010; Girichidis et al. 2011).”
Dispersal of molecular clouds by ionizing radiation (2012, background): “…from gravitational amplification of noise in the density field (Bonnell & Bate 2002) or from initial turbulence leading to density fluctuations which are subsequently enhanced by gravity (Heitsch et al. 2009; Ballesteros-Paredes et al. 2011,?; Walch et al. 2010, 2012; Girichidis et al. 2011, 2012).”
COLLAPSE OF MASSIVE MAGNETIZED DENSE CORES USING RADIATION MAGNETOHYDRODYNAMICS: EARLY FRAGMENTATION INHIBITION (2011, background): “Note that our initial conditions exhibit a relatively flat density profile, which should favor fragmentation (Girichidis et al. 2011).”
Physical Processes in the Interstellar Medium (2014, background): “Consequently, this process has been termed fragmentation-induced starvation (Peters et al., 2010a; Girichidis et al., 2011, 2012a).”
Stellar, brown dwarf and multiple star properties from a radiation hydrodynamical simulation of star cluster formation (2011, background): “The centrally condensed initial conditions of Krumholz et al. also favour the formation of massive stars (Girichidis et al. 2011), while uniform initial conditions result in the formation of many sub-clusters (Bonnell et al. 2003) which only later merge into a single cluster (Bate 2009a).”
The stellar and sub-stellar IMF of simple and composite populations (2011, background): “Generally, in order to propose that massive stars form in isolation rather contrived initial conditions in the cloud core are required such as a strong magnetic field, no turbulence and a highly peaked density profile (Girichidis et al. 2011).”
Inefficient star formation through turbulence, magnetic fields and feedback (2015, background): “The most likely reason for this discrepancy is that Wang et al. (2010) use a centrally concentrated density profile with ρ ∼ r−2 as an initial condition such that star formation in the centre of the cloud is much more violent than in the outskirts (Girichidis et al. 2011).”
FORMATION OF MASSIVE MOLECULAR CLOUD CORES BY CLOUD–CLOUD COLLISION (2013, background): “As discussed by Girichidis et al. (2011), whether a massive core successfully produces massive star(s) or not would depend on the detailed structure of the core.”