The Formation of the First Stars. I. The Primordial Star-forming Cloud

By V. Bromm, Paolo De Coppi, R. Larson. 2001

835 citations recorded by the source corpus.

To constrain the nature of the very first stars, we investigate the collapse and fragmentation of primordial, metal-free gas clouds. We explore the physics of primordial star formation by means of three-dimensional simulations of the dark matter and gas components, using smoothed particle hydrodynamics, under a wide range of initial conditions, including the initial spin, the total mass of the halo, the redshift of virialization, the power spectrum of the DM fluctuations, the presence of HD cooling, and the number of particles employed in the simulation. We find characteristic values for the temperature, T ~ a few 100 K, and the density, n ~ 103-104 cm-3, characterizing the gas at the end of the initial free-fall phase. These values are rather insensitive to the initial conditions. The corresponding Jeans mass is MJ ~ 103 M☉. The existence of these characteristic values has a robust explanation in the microphysics of H2 cooling, connected to the minimum temperature that can be reached with the H2 coolant, and to the critical density at which the transition takes place between levels being populated according to non-LTE (NLTE), and according to LTE. In all cases, the gas dissipatively settles into an irregular, central configuration that has a filamentary and knotty appearance. The fluid regions with the highest densities are the first to undergo runaway collapse due to gravitational instability, and to form clumps with initial masses ~103 M☉, close to the characteristic Jeans scale. These results suggest that the first stars might have been quite massive, possibly even very massive with M* ≳ 100 M☉. After a gas element has undergone runaway collapse, and has reached densities in excess of 108 cm-3, a sink particle is created. This procedure allows us to follow the evolution of the overall system beyond the point where the first nonlinear region would otherwise force the calculation to a halt. These later evolutionary stages, during which the clumps grow in mass due to accretion and merging with other clumps, are quite sensitive to the initial conditions. The key process in building up very massive clumps, with masses up to a few times 104 M☉, is merging between clumps. Since the merging rate sensitively depends on the density of the gas, halos with the highest degree of central concentration are able to assemble the most massive clumps. Among these are halos with a low spin (λ ≃ 0.01), and with DM fluctuations imprinted according to a white-noise spectrum.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/eb7a1fa76299a4f68c261a1a10602a4a239d1008

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Citations in the corpus

Self-regulated reionization (2006, background): “III) might have been quite massive (Bromm et al. 2002; Abel et al. 2000).”
The aftermath of the first stars: massive black holes (2006, neutral): “10 in Bromm et al. (2002)].”
The First Stars: Mass Growth Under Protostellar Feedback (2011, background): “As discussed in Bromm et al. (2002) and Stacy et al. (2010), our sink formation criteria well represent regions that will truly collapse to stellar densities.”
Formation of Supermassive Black Hole Seeds (2016, background): “In the absence of dust and metals, the cooling ability of the primordial gas is considerably reduced and the gas temperature is about a factor of 10-20 higher compared to the contemporary star formation in molecular clouds (Abel et al. 2002; Bromm et al. 2002).”
The VLT-FLAMES Survey of Massive Stars: Observations in the Galactic Clusters NGC 3293, NGC 4755 and NGC 6611 ⋆ (2005, background): “Theoretical simulations of star formation in the early Universe have suggested that masses larger than 100 M are strongly favoured (Bromm et al. 2002; Abel et al. 2002), and these “zero-metallicity” (or Population III) stars are considered to be prime candidates for the re-ionization of the…”
Observational evidence for intermediate-mass black holes (2017, background): “In the absence of metals (elements heavier than He and Li), gas cooling is only possible by means of atomic and molecular hydrogen (H2; e.g., Bromm et al. 1999, 2002; Bromm & Larson 2004).”
Population III Star Formation in a ΛCDM Universe. I. The Effect of Formation Redshift and Environment on Protostellar Accretion Rate (2006, background): “Bromm et al. (2002) do not have the mass and spatial resolution necessary to provide constraints.”
Early Cosmological H II/He III Regions and Their Impact on Second-Generation Star Formation (2006, background): “Three-dimensional simulations (Abel et al. 2002; Bromm et al. 2002; Yoshida et al. 2003, 2006) as well as onedimensional calculations (Omukai &Nishi 1998; Ripamonti et al. 2002) show that primordial gas clouds have steep density profiles / r n with n 2Y2.”
Formation of supermassive black holes (2010, background): “Simulations of the collapse of primordial molecular clouds (Bromm et al, 1999, 2002; Abel et al, 2000; Yoshida et al, 2006; Gao et al, 2007) suggest that the first generation of stars contained many ‘very massive stars’ (VMSs) with m?”
The Spin-Kinetic Temperature Coupling and the Heating Rate due to Lyα Scattering before Reionization: Predictions for 21 Centimeter Emission and Absorption (2003, background): “The dark ages ended at the time when the first stars formed in these halos where gas could cool for the first time, with a characteristic mass of ∼ 107M⊙ (Couchman & Rees 1986; Tegmark et al. 1997; Abel et al. 2000; Bromm et al. 2002).”
The Formation of the First Stars. II. Radiative Feedback Processes and Implications for the Initial Mass Function (2007, background): “In the absence of any elements heavier than helium (other than trace amounts of lithium) the chemistry and thermodynamics of the gas are very simple (Abel et al. 2002, hereafter ABN02; Bromm et al. 2002).”
WHAT NEXT-GENERATION 21 cm POWER SPECTRUM MEASUREMENTS CAN TEACH US ABOUT THE EPOCH OF REIONIZATION (2013, background): “…in high-redshift galaxy formation physics as to which halos host significant stellar populations (see e.g. Haiman et al. 1996, Abel et al. 2002 and Bromm et al. 2002 for lower mass limits on star-forming halos, and e.g. Mesinger & Dijkstra 2008 and Okamoto et al. 2008 for feedback effects which…”
Supermassive black hole formation during the assembly of pre-galactic discs (2006, background): “…remnants of the first generation of metal-free stars that form with an initial mass function that is biased towards higher masses (Abel et al. 2000; Bromm et al. 2002) provide the initial seed black holes with masses of the order of a 10’s to 100 M⊙ (Madau & Rees 2001; Volonteri et al. 2003;…”