Simulations of Pregalactic Structure Formation with Radiative Feedback

By M. Machacek, Greg L. Bryan, Tom Abel. 2000

304 citations recorded by the source corpus.

We present results from three-dimensional hydrodynamic simulations of the high-redshift collapse of pregalactic clouds including feedback effects from a soft H2 photodissociating UV radiation field. The simulations use an Eulerian adaptive mesh refinement technique to follow the nonequilibrium chemistry of nine chemical species with cosmological initial conditions drawn from a popular Λ-dominated cold dark matter model. The results confirm that the soft UV background can delay the cooling and collapse of small halos (~106 M☉). For reasonable values of the photodissociating flux, the H2 fraction is in equilibrium throughout most of the objects we simulate. We determine the mass threshold for collapse for a range of soft-UV fluxes and also derive a simple analytic expression. Continuing the simulations beyond the point of initial collapse demonstrates that the fraction of gas which can cool depends mostly on the virial mass of the halo and the amount of soft-UV flux, with remarkably little scatter. We parameterize this relation, for use in semianalytic models.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/bf7d93db9a48ae40c81f5a0ddd3d55f51c43fb11

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In Astronomy and Astrophysics

1. P. Hopkins
2. L. Hernquist
3. Volker Springel
4. A. Dekel
5. Tom Abel
6. John H. Wise
7. R. Dav'e
8. R. Somerville

Citations in the corpus

• The First Billion Years project: the impact of stellar radiation on the co-evolution of Populations II and III (2012, background): “…are critical for the cooling of the primordial gas, it is expected that their destruction leads to diminished rates of gas collapse and Pop III star formation (e.g. Omukai & Nishi 1999; Machacek et al. 2001; Mesinger et al. 2006a; Wise & Abel 2007; O’Shea & Norman 2008; Trenti et al. 2009).”
• Simulations of Early Structure Formation: Primordial Gas Clouds (2003, methodology): “However, as discussed in Machacek et al. (2001), neglecting this process does not affect our results because of the high densities in the core regions where molecular hydrogen formation reactions (via the H− channel) occur significantly faster than photodetachment for the radiation intensities we…”
• GALAXY PROPERTIES AND UV ESCAPE FRACTIONS DURING THE EPOCH OF REIONIZATION: RESULTS FROM THE RENAISSANCE SIMULATIONS (2016, methodology): “LW radiation may significantly delay the Pop III formation in low-mass halos (Machacek et al. 2001; Wise & Abel 2007; O’Shea & Norman 2008), and thus the enrichment history and the emergence of metal-enriched stars in those halos.”
• Population III Star Formation in a ΛCDM Universe. I. The Effect of Formation Redshift and Environment on Protostellar Accretion Rate (2006, background): “Some previous work has studied large numbers of primordial halos (Machacek et al. 2001, 2003; Yoshida et al. 2003).”
• Second-Generation Objects in the Universe: Radiative Cooling and Collapse of Halos with Virial Temperatures above 104 K (2001, background): “For this reason, H2 formation and cooling is thought to be inhibited in T < 104 K halos due to the effects of an external UV-dissociating background (Haiman, Rees, & Loeb 1997; Ciardi et al. 2000; Haiman et al. 2000; Machacek et al. 2001).”
• Supermassive black hole formation by direct collapse: keeping protogalactic gas H2 free in dark matter haloes with virial temperatures Tvir > rsim 104 K (2009, background): “The critical value has been found to be J21 ∼ 0.1 (Haiman et al. 1997; Machacek et al. 2001, 2003; Mesinger et al. 2006, 2008; Wise & Abel 2007; O’Shea & Norman 2008; here and in the rest of the paper, J21 denotes the specific intensity just below 13.6eV, in the usual units of 10−21erg cm−2 sr−1…”
• Resolving the Formation of Protogalaxies. II. Central Gravitational Collapse (2007, background): “The Lyman-Werner radiation from massive stars can dissociate H2 from large distances (Dekel &Rees 1987; Haiman et al. 2000), suppress star formation in lower mass halos (Machacek et al. 2001; Wise & Abel 2005), and should be considered to accurately model future star formation.”
• Dark Matter Subhalos and the Dwarf Satellites of the Milky Way (2008, background): “This is large enough to efficiently cool the gas and allow it to collapse and form stars within a Hubble time unless significant heating occurs during this phase (e.g. Machacek et al. 2001; Yoshida et al. 2003; Kuhlen & Madau 2005).”
• Star Formation at Very Low Metallicity. I. Chemistry and Cooling at Low Densities (2007, background): “The simplest approach is to ignore self-shielding entirely (see, e.g., Machacek et al. 2001, 2003).”
• IONIZING PHOTON ESCAPE FRACTIONS FROM HIGH-REDSHIFT DWARF GALAXIES (2008, background): “Gas condensation in the lower mass H2 cooling halos can be delayed by a H2 dissociating UV (Lyman-Werner) background between 11.2 and 13.6 eV (Machacek et al. 2001; Wise & Abel 2007b; O’Shea & Norman 2008).”
• THE MASS SPECTRUM OF THE FIRST STARS (2014, background): “The LW background intensity in unit of 10−21 cgs is as strong as 0.01–0.1 at z ∼ 10 (e.g., Ahn et al. 2012), which could prevent the gas from cooling by destroying the H2 molecules (Machacek et al. 2001; Yoshida et al. 2003; O’Shea & Norman 2008).”