GRAVITATIONAL FRAGMENTATION IN TURBULENT PRIMORDIAL GAS AND THE INITIAL MASS FUNCTION OF POPULATION III STARS

By P. C. Clark, S. Glover, Ralf Klessen, Volker Bromm. 2010

236 citations recorded by the source corpus.

We report results from numerical simulations of star formation in the early universe that focus on the dynamical behavior of metal-free gas under different initial and environmental conditions. In particular we investigate the role of turbulence, which is thought to ubiquitously accompany the collapse of high-redshift halos. We distinguish between two main cases: the birth of Population III.1 stars—those which form in the pristine halos unaffected by prior star formation—and the formation of Population III.2 stars—those forming in halos where the gas has an increased ionization fraction. We find that turbulent primordial gas is highly susceptible to fragmentation in both cases, even for turbulence in the subsonic regime, i.e., for rms velocity dispersions as low as 20% of the sound speed. Fragmentation is more vigorous and more widespread in pristine halos compared to pre-ionized ones. If such levels of turbulent motions were indeed present in star-forming minihalos, Population III.1 stars would be on average of somewhat lower mass, and form in larger groups, than Population III.2 stars. We find that fragment masses cover over two orders of magnitude, suggesting that the Population III initial mass function may have been much broader than previously thought. This prompts the need for a large, high-resolution study of the formation of dark matter minihalos that is capable of resolving the turbulent flows in the gas at the moment when the baryons become self-gravitating. This would help to determine the applicability of our results to primordial star formation.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/782df7ec37a1f6a6cc3660aa63c929d476922284

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In Astronomy and Astrophysics

1. P. Hopkins
2. L. Hernquist
3. Volker Bromm
4. S. Glover
5. Volker Springel
6. Ralf Klessen
7. R. Dav'e
8. M. Volonteri

Citations in the corpus

• Doing Science with eLISA: Astrophysics and Cosmology in the Millihertz Regime (2012, background): “The formation of Pop III stars remains a poorly understood process (Zinnecker and Yorke, 2007) and the maximum mass reached by individual stars is unknown (see, e.g., Clark et al., 2011).”
• CANDELS: THE CONTRIBUTION OF THE OBSERVED GALAXY POPULATION TO COSMIC REIONIZATION (2012, result): “This conclusion has been strengthened by recent simulation results which have corrected the mass scale of the first stars down to less extreme values (Clark et al. 2011; Greif et al. 2011, 2012).”
• 21 cm cosmology in the 21st century (2011, background): “1 − 1 M stars may be the preferred channel of star formation [75].”
• THE SPECTRAL EVOLUTION OF THE FIRST GALAXIES. I. JAMES WEBB SPACE TELESCOPE DETECTION LIMITS AND COLOR CRITERIA FOR POPULATION III GALAXIES (2011, background): “However, this pop III.1 (∼ 100 M⊙) versus pop III.2 (∼ 10 M⊙) picture is looking increasingly uncertain, as the latest simulations indicate more fragmentation than before, with lower pop III masses as a result (e.g. Stacy et al. 2008; Clark et al. 2011; Greif et al. 2011a).”
• The Close Binary Fraction of Solar-type Stars Is Strongly Anticorrelated with Metallicity (2018, background): “Similarly, Clark et al. (2011a, 2011b) demonstrated that the disks of primordial Population III stars are highly susceptible to fragmentation.”
• Titans of the early Universe: The Prato statement on the origin of the first supermassive black holes (2018, background): “As the disk grows in mass it may become gravitationally unstable, fragment, and form multiple objects (Clark et al. 2011a, 2011b; Smith et al. 2011; Greif et al. 2012; Regan et al. 2014; Sakurai et al. 2016).”
• A NEW JEANS RESOLUTION CRITERION FOR (M)HD SIMULATIONS OF SELF-GRAVITATING GAS: APPLICATION TO MAGNETIC FIELD AMPLIFICATION BY GRAVITY-DRIVEN TURBULENCE (2011, methodology): “For a similar approach see Clark et al. (2008, 2011) Although the existence of magnetic fields on a wide range of astrophysical scales is clear, their origin is still poorly understood.”
• Formation and evolution of primordial protostellar systems (2012, background): “For example, in Clark et al. (2011b) the first sink particle formed after 100 yr at about 10 au from the primary protostar, while in the present study we only capture the first 10 yr, and the protostars form within a few au, which is close to the accretion radius of the sink particles.”
• THE GENERATION OF STRONG MAGNETIC FIELDS DURING THE FORMATION OF THE FIRST STARS (2010, background): “Recent hydrodynamical simulations [19] suggest that the primordial gas is highly susceptible to fragmentation even for subsonic turbulence.”
• SIMULATIONS ON A MOVING MESH: THE CLUSTERED FORMATION OF POPULATION III PROTOSTARS (2011, background): “As proposed by Clark et al. (2011b), in all five minihalos a circumstellar disk forms that fragments vigorously into a small cluster of protostars with a range of masses.”
• The First Stars (2012, methodology): “More recently, a study by Clark et al. (2011b) has dramatically improved the mass resolution used to model the build-up of a protostellar accretion disk around the first Population III protostar.”
• THE MASS SPECTRUM OF THE FIRST STARS (2014, methodology): “We set the sink radius rsink to 30 AU, but the previous higher-resolution studies of rsink 1 AU (with short time integration) revealed that the disk within 30 AU also fragments into secondary stars (e.g., Clark et al. 2011b; Greif et al. 2012).”
• THE MOST METAL-POOR STARS. IV. THE TWO POPULATIONS WITH [Fe/H] ≲ −3.0 (2012, background): “25 We recognize that the detail of the mass function of the first stars is the subject of ongoing investigation (see, e.g., Clark et al. 2011 and Dopcke et al. 2012).”
• Possible indirect confirmation of the existence of Pop III massive stars by gravitational wave (2014, background): “(83) This mass function is suggested by some numerical simulations of the Pop III star formation (Clark et al. 2011).”
• The First Stars: Mass Growth Under Protostellar Feedback (2011, methodology): “The fragmentation of primordial gas and growth of Pop III stars has recently been modeled from cosmological c© 2011 RAS, MNRAS 000, 1–21 initial conditions with resolution reaching nearly protostellar scales (Clark et al. 2011b, Greif et al. 2011).”
• Building up the Population III initial mass function from cosmological initial conditions (2016, methodology): “More recent simulations have found that fragmentation of the central gas configuration will instead allow for a wider range of Pop III masses (e.g. Clark et al 2008; 2011a; Turk et al. 2009; Stacy et al. 2010; Stacy & Bromm 2013, 2014).”
• GRACKLE: a chemistry and cooling library for astrophysics (2016, unknown): “Key: 1 – Igarashi & Lin (1999); 2 – Zhao et al. (2000); 3 – Savin (2002); 4 – Gerlich (1982); 5 – Galli & Palla (2002); 6 – Mielke et al. (2003); 7 – Clark et al. (2011); 8 – Shavitt (1959); 9 – Ripamonti (2007); 10 – Kreckel et al. (2010); 11 – Miller et al. (2012) Bromm 2006; McGreer & Bryan…”
• The stellar and sub-stellar IMF of simple and composite populations (2011, background): “Star-formation in the very early universe must have therefore produced topheavy IMFs (Larson 1998; Bromm et al. 2001; Clark et al. 2011).”