The First Stellar Cluster

By P. C. Clark, S. Glover, Ralf Klessen. 2007

178 citations recorded by the source corpus.

We report results from numerical simulations of star formation in the early universe that focus on gas at very high densities and very low metallicities. We argue that the gas in the central regions of protogalactic halos will fragment as long as it carries sufficient angular momentum. Rotation leads to the build-up of massive disklike structures which fragment to form protostars. At metallicities Z ≈ 10−5 Z☉, dust cooling becomes effective and leads to a sudden drop of temperature at densities above n = 1012 cm−3. This induces vigorous fragmentation, leading to a very densely packed cluster of low-mass stars. This is the first stellar cluster. The mass function of stars peaks below 1 M☉, similar to what is found in the solar neighborhood and comparable to the masses of the very low metallicity subgiant stars recently discovered in the halo of our Milky Way. We find that even purely primordial gas can fragment at densities 1014 cm −3 ⩽ n⩽ 1016 cm −3, although the resulting mass function contains only a few objects (at least a factor of 10 fewer than the Z = 10−5 Z☉ mass function) and is biased toward higher masses. A similar result is found for gas with Z = 10−6 Z☉. Gas with Z ⩽ 10−6 Z☉ behaves roughly isothermally at these densities (with polytropic exponent γ ≈ 1.06), and the massive disklike structures that form due to angular momentum conservation will be marginally unstable. As fragmentation is less efficient, we expect stars with Z ⩽ 10−6 Z☉ to be massive, with masses in excess of several tens of solar masses, consistent with the results from previous studies.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/56594595eeefffcbee3a239c730288f5e49e31c1

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Citations in the corpus

THE MASS SPECTRUM OF THE FIRST STARS (2014, background): “On the other hand, recent advances in the studies of the mass accretion phase of the first star formation revealed that the mass of the first stars could be smaller than expected before (Clark et al. 2008; Smith et al. 2011).”
Importance of the Initial Conditions for Star Formation - I. Cloud Evolution and Morphology (2010, background): “Clark, Glover & Klessen (2008b), Clark et al. (2008a), Offner et al. (2008) and Krumholz et al. (2007) do not specify the nature of the modes they select for their turbulence.”
Formation of supermassive black holes (2010, background): “As mentioned, it is not clear if the very first stars formed in singles or multiples per halo, with the latter option leading to a less top-heavy mass function (Clark et al, 2008a; Stacy et al, 2009; Turk et al, 2009).”
FORMATION OF THE FIRST NUCLEAR CLUSTERS AND MASSIVE BLACK HOLES AT HIGH REDSHIFT (2008, background): “On the other hand, if the gas has been enriched to a certain level, fragmentation can take place and an entire stellar cluster is formed (Clark et al. 2008).”
Can Supermassive Black Holes Form in Metal-enriched High-Redshift Protogalaxies? (2008, methodology): “However, in this regime we find P 0:5 as shown in Figure 9; fragmentation has also been confirmed to occur in two independent hydrodynamic simulations of collapsing clouds not irradiated by external FUV fields (Tsuribe & Omukai 2006; Clark et al. 2008).”
Formation and evolution of primordial protostellar systems (2012, background): “…of the Royal Astronomical Society C© 2012 RAS Downloaded from https://academic.oup.com/mnras/article-abstract/424/1/399/1009176 by guest on 26 July 2018 on to the disc and the efficient cooling of the disc by molecular hydrogen (Clark et al. 2008, 2011a,b; Stacy et al. 2010; Greif et al. 2011a).”
The First Stars: Mass Growth Under Protostellar Feedback (2011, background): “Simulations by Clark et al. (2008, 2011a) employing idealized initial conditions found that primordial star-forming gas can undergo fragmentation to form Pop III multiple systems, while the simulations of Turk et al. (2009) and Stacy et al. (2010) established such fragmentation also when…”
A NEW JEANS RESOLUTION CRITERION FOR (M)HD SIMULATIONS OF SELF-GRAVITATING GAS: APPLICATION TO MAGNETIC FIELD AMPLIFICATION BY GRAVITY-DRIVEN TURBULENCE (2011, methodology): “…it became clear that primordial gas becomes highly turbulent during the formation of the first galaxies and stars as well (e.g., Abel et al. 2002; O’Shea & Norman 2007; Wise & Abel 2007; Clark et al. 2008; Greif et al. 2008), which has far-reaching consequences for all cosmic structure formation.”
Building up the Population III initial mass function from cosmological initial conditions (2016, background): “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).”
LIMITING ACCRETION ONTO MASSIVE STARS BY FRAGMENTATION-INDUCED STARVATION (2010, background): “Indeed, current numerical simulations provide the first hints that this might be the case (Clark et al. 2008; Turk et al. 2009; Stacy et al. 2010).”
FORMATION RATES OF POPULATION III STARS AND CHEMICAL ENRICHMENT OF HALOS DURING THE REIONIZATION ERA (2009, background): “When the second-generation halo has a virial temperature Tvir ≈ 104 K, the metallicity of its gas is expected to have been enriched to Z 10−4 Z , high enough to mark a transition toward a different mode of star formation, especially if some dust is present (Schneider et al. 2006; Clark et al. 2008).”
The Formation of the First Stars. II. Radiative Feedback Processes and Implications for the Initial Mass Function (2007, background): “…gravitational fragmentation ismuch less effective: indeed, numerical simulations show no evidence for it (e.g., ABN02; Yoshida et al. 2006; but see Clark et al. 2008), and analytic calculations (Ripamonti & Abel 2004), including those that consider disk fragmentation (Tan & Blackman 2004), show…”
Resolving the Formation of Protogalaxies. II. Central Gravitational Collapse (2007, methodology): “Using the stellar formation conditions plus this condition and allowing the particle to accrete (i.e., sink particles; Bate et al. 1995; Krumholz et al. 2004), protogalactic collapses can be followed in cosmological hydrodynamic simulations (Clark et al. 2008).”