2 research outputs found
The Birth of a Galaxy - III. Propelling reionisation with the faintest galaxies
Starlight from galaxies plays a pivotal role throughout the process of cosmic
reionisation. We present the statistics of dwarf galaxy properties at z > 7 in
haloes with masses up to 10^9 solar masses, using a cosmological radiation
hydrodynamics simulation that follows their buildup starting with their
Population III progenitors. We find that metal-enriched star formation is not
restricted to atomic cooling ( K) haloes, but can occur
in haloes down to masses ~10^6 solar masses, especially in neutral regions.
Even though these smallest galaxies only host up to 10^4 solar masses of stars,
they provide nearly 30 per cent of the ionising photon budget. We find that the
galaxy luminosity function flattens above M_UV ~ -12 with a number density that
is unchanged at z < 10. The fraction of ionising radiation escaping into the
intergalactic medium is inversely dependent on halo mass, decreasing from 50 to
5 per cent in the mass range . Using our galaxy
statistics in a semi-analytic reionisation model, we find a Thomson scattering
optical depth consistent with the latest Planck results, while still being
consistent with the UV emissivity constraints provided by Ly forest
observations at z = 4-6.Comment: 21 pages, 15 figures, 4 tables. Accepted in MNRA