The Fragmentation of Pre-enriched Primordial Objects

By Volker Bromm, A. Ferrara, Paolo De Coppi, R. Larson. 2001

354 citations recorded by the source corpus.

Recent theoretical investigations have suggested that the formation of the very first stars, forming out of metal-free gas, was fundamentally different from the present-day case. The question then arises which effect was responsible for this transition in the star formation properties. In this paper, we study the effect of metallicity on the evolution of the gas in a collapsing dark matter mini-halo. We model such a system as an isolated 3σ peak of mass that collapses at , using smoothed particle hydrodynamics. The gas has a supposed level of pre-enrichment of either or 10−3 Z⊙. We assume that H2 has been radiatively destroyed by the presence of a soft UV background. Metals therefore provide the only viable cooling at temperatures below 104 K. We find that the evolution proceeds very differently for the two cases. The gas in the lower metallicity simulation fails to undergo continued collapse and fragmentation, whereas the gas in the higher metallicity case dissipatively settles into the centre of the dark matter halo. The central gas, characterized by densities , and a temperature, , that closely follows that of the cosmic microwave background, is gravitationally unstable and undergoes vigorous fragmentation. We discuss the physical reason for the existence of a critical metallicity, , and its possible dependence on redshift. Compared with the pure H/He case, the fragmentation of the gas leads to a larger relative number of low-mass clumps.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/239de9b3a88cdc50e50147bf3e235dffc10ff545

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. Volker Bromm
2. L. Hernquist
3. Tom Abel
4. John H. Wise
5. S. Glover
6. A. Ferrara
7. P. Hopkins
8. Ralf Klessen

In Nuclear and High Energy Physics

1. S. Furlanetto
2. A. Mesinger
3. L. Hernquist
4. A. Ferrara
5. M. Zaldarriaga
6. S. Oh
7. Abraham Loeb
8. Volker Bromm

Citations in the corpus

• First stars V - Abundance patterns from C to Zn and supernova yields in the early Galaxy (2003, background): “Theoretical work (Bromm et al. 2001 and references therein) predict that the first stellar generation is made of very massive stars, with masses above 100 M⊙, because zero-metal matter lacks adequate cooling mechanisms for fragmenting down to classical supernova-progenitor masses.”
• Chemical Evolution in Hierarchical Models of Cosmic Structure. I. Constraints on the Early Stellar Initial Mass Function (2005, background): “As explained below, the initial focus is on deriving empirical constraints on the first-stars IMF, as a complement to purely theoretical approaches that are being pursued by many groups (Bromm et al. 2001; Abel et al. 2002; Omukai et al. 2005; Tan & McKee 2004).”
• The First Billion Years project: the impact of stellar radiation on the co-evolution of Populations II and III (2012, background): “…star-forming gas, the IMF shifts rapidly from that of Pop III stars to a much more bottom-heavy IMF, with characteristic stellar masses much like those in the present-day Universe (e.g. Bromm et al. 2001; Schneider et al. 2003; Omukai et al. 2005; Santoro & Shull 2006; Dopcke et al. 2011, 2012).”
• Fluctuations in the high-redshift Lyman–Werner background: close halo pairs as the origin of supermassive black holes (2008, background): “They suggest that gas fragmentation may thus be inevitable above a critical metallicity, whose value is between Zcr ≈ 3 × 10−4Z⊙ (in the absence of dust) and as low as Zcr ≈ 5 × 10−6Z⊙ (with a dust-to-gas mass ratio of about 0.01Z/Z⊙, also see Omukai 2000, Bromm et al. 2001, Schneider et al. 2003).”
• Population III stars: hidden or disappeared? (2007, result): “This idea has been later on expanded and substantiated by a number of detailed studies (Omukai 2000; Bromm et al. 2001; Schneider et al. 2002, 2003).”
• Blossoms from black hole seeds: properties and early growth regulated by supernova feedback (2016, background): “In the “PopIII star remnants” scenario, BHs are predicted to form in mini-haloes (Mh ≈ 105 M ) with gas below a critical metallicity (Z < 10−3.5 Z , Bromm et al. 2001; Schneider et al. 2002) at redshift z = 30−20 from the remnants of the first generation of stars (PopIII, Madau & Rees 2001;…”
• THE BIRTH OF A GALAXY: PRIMORDIAL METAL ENRICHMENT AND STELLAR POPULATIONS (2010, background): “…SchlossWolfsbrunnenweg 35, 69118 Heidelberg, Germany metallicity that is ∼ 10−6Z⊙ if dust cooling is efficient (Omukai et al. 2005; Schneider et al. 2006; Clark et al. 2008) and ∼ 10−3.5Z⊙ otherwise (Bromm et al. 2001; Smith et al. 2009), where the gas can cool rapidly, lowering its Jeans mass.”
• The Distribution of Metallicity in the Intergalactic Medium at z ~ 2.5: O VI and C IV Absorption in the Spectra of Seven QSOs (2003, background): “Bromm et al. (2001) have shown that massive, H2 cooled stars will not form from gas with metallicity above this value, as atomic line cooling becomes too efficient to maintain large scale stability, and a collapsing cloud fragments into smaller mass units.”
• FORMATION RATES OF POPULATION III STARS AND CHEMICAL ENRICHMENT OF HALOS DURING THE REIONIZATION ERA (2009, background): “Calculations by Bromm et al. (2001) found that a region containing up to about 108 M can be enriched to a critical metallicity Zcrit 10−4 Z by the most massive pair-instability supernovae.”
• Modeling the Radio Background from the First Black Holes at Cosmic Dawn: Implications for the 21 cm Absorption Amplitude (2018, background): “Fortunately, it is expected that Pop-III formation naturally ends once the metallicity of gas reaches ≈10−6–10−3 Ze (Bromm et al. 2001; Omukai et al. 2005) and while a number of models show that Pop-III formation can continue down to redshifts of z10, we have shown that the additional Lyman–Werner…”
• Probing the formation of the first low‐mass stars with stellar archaeology (2007, background): “1M⊙) Pop II stars, additional metal coolants, generated in the first supernovae, are required (e.g. Omukai 2000; Bromm et al. 2001).”
• The cooling of shock-compressed primordial gas (2005, background): “In much of the literature, it is assumed that metals are required to lower the temperature of interstellar gas to the CMB temperature (e.g. Bromm et al. 2001; Schneider et al. 2002; Clarke & Bromm 2003).”
• First Stars, Very Massive Black Holes, and Metals (2001, methodology): “Following the results of numerical simulations at different resolutions (Bromm et al. 2001, Abel et al. 2000) we assume that ≈ 1/2 of the total available gas is utilized in star formation, the rest remaining in diffuse form.”
• Statistical Probes of Reionization with 21 Centimeter Tomography (2004, background): “Suppose that the first generation consisted of massive, metal-free stars; the natural self-regulation condition halts the formation of these stars when the metallicity in collapsed objects passes some threshold (Bromm et al. 2001a; Mackey et al. 2003; Yoshida et al. 2003).”
• The first galaxies : assembly, cooling and the onset of turbulence (2008, background): “On the other hand, if mergers are absent or incoming haloes are not sufficiently massive, accretion could be suppressed for & 100 Myr (Johnson & Bromm 2007).”
• Formation of the First Stars by Accretion (2003, background): “A metal abundance as low as 10 4 Z can influence the fragmentation mass scale of star-forming clouds (Omukai 2000; Bromm et al. 2001a; Schneider et al. 2002).”