Abstract
AbstractThe first stars are believed to have formed a few hundred million years after the big bang in so-called dark matter minihalos with masses $\sim 10^{6}\mbox{ M}_{\odot}$ ∼ 10 6 M ⊙ . Their radiation lit up the Universe for the first time, and the supernova explosions that ended their brief lives enriched the intergalactic medium with the first heavy elements. Influenced by their feedback, the first galaxies assembled in halos with masses $\sim10^{8}\mbox{ M}_{\odot}$ ∼ 10 8 M ⊙ , and hosted the first metal-enriched stellar populations. In this review, I summarize the theoretical progress made in the field of high-redshift star and galaxy formation since the turn of the millennium, with an emphasis on numerical simulations. These have become the method of choice to understand the multi-scale, multi-physics problem posed by structure formation in the early Universe. In the first part of the review, I focus on the formation of the first stars in minihalos - in particular the post-collapse phase, where disk fragmentation, protostellar evolution, and radiative feedback become important. I also discuss the influence of additional physical processes, such as magnetic fields and streaming velocities. In the second part of the review, I summarize the various feedback mechanisms exerted by the first stars, followed by a discussion of the first galaxies and the various physical processes that operate in them.
Highlights
1 Introduction The formation of the first stars marked a fundamental transition in the history of the Universe. They initiated the transformation of the homogeneous intergalactic medium (IGM) to one filled with the rich structure we observe today
Ending the so-called ‘cosmic dark ages’, when the Universe contained no visible light, they lit up the Universe at redshifts z (Bromm and Larson ; Glover, ; Bromm ). They formed at the center of dark matter (DM) ‘minihalos’ with virial masses Mvir ∼ M, which are the smallest building blocks in the hierarchy of galaxy formation. These objects accrete the pure hydrogen and helium gas forged in the Big Bang, and after continued cooling and contraction form a stellar embryo that begins to accrete from the surrounding gas cloud
During the initial stages of the collapse, the level populations of H are not yet populated according to local thermal equilibrium (LTE), and the cooling rate scales as
Summary
The formation of the first stars marked a fundamental transition in the history of the Universe. Despite the complications brought about by these processes, it is likely that Population III stars were much more massive than present-day stars They are strong emitters of ultraviolet (UV) radiation, which heats the IGM and begins the process of reionization (Loeb and Barkana ; Ciardi and Ferrara ; Fan et al ; Stiavelli ). In Section , I give a brief introduction to structure formation in the high-redshift Universe, followed by a description of the collapse of gas in minihalos. Feedback by Population III is summarized in Ciardi and Ferrara ( )
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