UV regulated star formation in high-redshift galaxies

Muhammad A. Latif, Sadegh Khochfar

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)


The first galaxies forming a few hundred million years after the big bang are the key drivers of cosmic evolution and ideal laboratories to study theories of galaxy formation. We here study the role of UV radiation in suppressing star formation in primordial galaxies by destroying molecular hydrogen, the main coolant in primordial gas, and provide estimates of cold dense gas at the onset of star formation. To accomplish this goal, we perform three-dimensional cosmological simulations of minihaloes in different environments forming at z ∼ 25 by varying strength of background UV flux below the Lyman limit between 0.01-1000 in units of J21 = 10−21 erg cm−2 s−1 Hz−1 sr−1. Particularly, we include photodetachment of H, the self-shielding of H2, which both were neglected in previous studies and use updated reaction rates. Our results show that depending on the background level H2 formation is suppressed, delaying gravitational collapse until haloes reach the atomic cooling limit. We find that the formation of cold dense molecular gas and subsequently star formation gets delayed by 100-230 Myr depending on the level of the background radiation and the growth history of the dark matter haloes. The fraction of dense self-shielded gas is a strong function of the background flux and exponentially declines with the strength of incident UV flux above J21 ≥ 1. We find that taking into account H2 self-shielding is crucial for accurately estimating the amount of cold dense gas available for star formation.

Original languageEnglish
Pages (from-to)2706-2716
Number of pages11
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Publication statusPublished - Dec 1 2019


  • Cosmology: theory
  • Early Universe
  • Methods: numerical

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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