Cosmological production of H2 before the formation of the first galaxies

Hirata, Christopher M.; Padmanabhan, Nikhil

doi:10.1111/j.1365-2966.2006.10924.x

Cited by 59 publications

(87 citation statements)

References 60 publications

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“…Table 3 gives the abundances at redshifts z = 1000, z = 100 and z = 10. The initial relative abundance of hydrogen is very close in our three chemistry models SBBC, NSBBC1 and NSBBC2 (see Table 1), as is the case for show the abundances we would obtain without the correction of Hirata & Padmanabhan (2006) relative to the radiation emitted during the hydrogen recombination. Table 3.…”

Section: Hydrogenmentioning

confidence: 78%

“…The amount of H 2 molecules created during the Dark Ages is important and converge to the following values at z = 10: [H 2 ] SBBC = n H 2 /n b = 2.7 ×10 −7 . The effect of the correction of Hirata & Padmanabhan (2006) is shown on Fig. 5.…”

Section: Hydrogenmentioning

confidence: 99%

“…For that reaction, we consider the important correction described in Hirata & Padmanabhan (2006) that takes into account the effects of the non-thermal radiation emitted during hydrogen recombination. Figure 5 shows the evolution of the hydrogen chemistry in the standard model.…”

Section: Hydrogenmentioning

confidence: 99%

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Chemistry of heavy elements in the Dark Ages

Vonlanthen¹,

Rauscher

Winteler

et al. 2009

A&A

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Context. Primordial molecules were formed during the Dark Ages, i.e. the time between recombination and reionization in the early Universe. They were the constituents of the first proto-stellar clouds. Standard Big Bang nucleosynthesis predicts the abundances of hydrogen, helium, lithium, beryllium, and their isotopes in the early Universe. Heavier nuclei such as carbon, nitrogen, or oxygen are only formed in trace amounts. In nonstandard Big Bang nucleosynthesis models, it is possible to synthesize greater quantities of these heavier elements. The latter are interesting because they can form molecules with a high electric dipole moment which can increase the cooling in collapsing protostellar structures. Aims. The purpose of this article is to analyze the formation of primordial molecules based on heavy elements during the Dark Ages, with elemental abundances taken from different nucleosynthesis models. Methods. We present calculations of the full nonlinear equation set governing the primordial chemistry. We considered the evolution of 45 chemical species and used an implicit multistep method of variable order of precision with an adaptive stepsize control. Results. The cosmological recombination of heavy elements is presented for the first time. We find that the most abundant Dark Age molecules based on heavy elements are CH and OH. When considering initial conditions given by the standard Big Bang nucleosynthesis model, we obtain relative abundances [CH] = n CH /n b = 6.2 × 10 −21 and [OH] = n OH /n b = 1.2 × 10 −23 at z = 10, where n b is the total number density. But nonstandard nucleosynthesis can lead to higher heavy element abundances, while still satisfying the observed primordial light abundances. In that case, we show that the abundances of molecular species based on C, N, O, and F can be enhanced by two orders of magnitude, leading to a CH relative abundance higher than that of HD + or H 2 D + .

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Section: Hydrogenmentioning

confidence: 78%

Section: Hydrogenmentioning

confidence: 99%

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Chemistry of heavy elements in the Dark Ages

Vonlanthen¹,

Rauscher

Winteler

et al. 2009

A&A

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“…Hirata & Padmanabhan (2006) recently revised postrecombination calculations of the early universe. They argue that H þ 2 formation via…”

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confidence: 99%

Early Cosmological Hii/HeiiiRegions and Their Impact on Second‐Generation Star Formation

Yoshida¹,

Oh²,

Kitayama³

et al. 2007

ApJ

210

277

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We present the results of three-dimensional radiation hydrodynamics simulations of the formation and evolution of early H ii/He iii regions around the first stars. Cooling and recollapse of the gas in the relic H ii region is also followed in a full cosmological context, until second-generation stars are formed. We first carry out ray-tracing simulations of ionizing radiation transfer from the first star. Hydrodynamics is directly coupled with photoionization heating as well as radiative and chemical cooling. The photoionized hot gas is evacuated out of the host halo at a velocity of $30 km s À1. This radiative feedback effect quenches further star formation within the halo for over tens to a hundred million years. We show that the thermal and chemical evolution of the photoionized gas in the relic H ii region is remarkably different from that of a neutral primordial gas. Efficient molecular hydrogen production in the recombining gas enables it to cool to $100 K, where fractionation of HD/H 2 occurs. The gas further cools by HD line cooling down to a few tens of kelvins. Interestingly, at high redshifts (z > 10), the minimum gas temperature is limited by that of the cosmic microwave background with T CMB ¼ 2:728(1þ z). The gas cloud experiences runaway collapse when its mass is $40 M , which is significantly smaller than a typical clump mass of $200Y300 M for early primordial gas clouds. We argue that massive, rather than very massive, primordial stars may form in the relic H ii region. Such stars might be responsible for early metal enrichment of the interstellar medium from which recently discovered hyperYmetal-poor stars were born.

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“…Following this second period of growth, the fractional abundance of H 2 is of the order of 10 −6 , and H 2 is the most abundant molecule in the gas. However, this is still far smaller than the typical amount † This simple picture is complicated somewhat by the presence of non-thermal photons produced during hydrogen recombination that slightly distort the spectral shape of the CMB (Switzer & Hirata 2005;Hirata & Padmanabhan 2006), but even in this case the general principle is the same. 316 S. C. O. Glover of H 2 produced within the earliest star-forming protogalaxies, and hence although the chemical evolution of the pregalactic gas is interesting, it is of limited influence: almost all of the chemistry affecting the formation of the first stars and galaxies occurs within the protogalaxies themselves, as I explore in more detail in the next section.…”

mentioning

confidence: 95%

The Chemistry of the Early Universe

Glover

2011

Proc. IAU

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Abstract. The chemistry of the early Universe is a fascinating field of study. Even in the absence of any elements heavier than lithium, a surprising degree of chemical complexity proves to be possible, giving the topic considerable interest in its own right. In addition, the fact that molecular hydrogen plays a key role in the formation of the first stars and galaxies means that if we want to understand the formation of these objects, we must first develop a good understanding of the chemical evolution of the gas. In this review, I first give a brief introduction to the chemistry occurring in the gas prior to the formation of the first stars and galaxies, and then go on to discuss in more detail the main chemical processes occurring during the gravitational collapse of gas from intergalactic to protostellar densities, and how these processes influence the final outcome of the collapse.

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Cosmological production of H2 before the formation of the first galaxies

Cited by 59 publications

References 60 publications

Chemistry of heavy elements in the Dark Ages

Chemistry of heavy elements in the Dark Ages

Early Cosmological Hii/HeiiiRegions and Their Impact on Second‐Generation Star Formation

The Chemistry of the Early Universe

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