Аннотация
Reionisation in the early Universe is likely driven by dwarf galaxies. Using
cosmological, zoom-in, radiation-hydrodynamic simulations, we study the escape
of Lyman continuum (LyC) photons from mini-haloes with $M_halo łe
10^8\,M_ødot$. Our simulations include a new thermo-turbulent star formation
model, non-equilibrium chemistry, and relevant stellar feedback processes
(photoionisation by young massive stars, radiation pressure, and mechanical
supernova explosions). We find that the photon number-weighted mean escape
fraction in mini-haloes is higher ($\sim20$-$40\%$) than that in atomic-cooling
haloes, although the instantaneous fraction in individual haloes varies
significantly. The escape fraction from Pop III stars is found to be
significant ($\ge10\%$) only when the mass is greater than $\sim$100\,\msun.
Because star formation is stochastic and dominated by a few gas clumps, the
escape fraction is generally determined by radiation feedback (heating due to
photo-ionisation), rather than supernova explosions. We find that the resulting
stellar mass of the proto-galaxies in mini-haloes follows the slope and
normalisation reported in Kimm & Cen, which is similar to the empirical
stellar mass-to-halo mass relation derived in the local Universe. Based on
simple analytic calculations, we show that LyC photons from mini-haloes are,
despite their high escape fractions, of minor importance for reionisation, as
feedback reduces star formation very efficiently in mini-haloes. We confirm
previous claims that stars in atomic-cooling haloes with masses
$10^8\,M_ødotM_halo 10^11\,M_ødot$ are likely to be the most
important source of reionisation.
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