%0 Generic %1 wise2014birth %A Wise, John H. %A Demchenko, Vasiliy G. %A Halicek, Martin T. %A Norman, Michael L. %A Turk, Matthew J. %A Abel, Tom %A Smith, Britton D. %D 2014 %K dwarf galaxy reionization %T The Birth of a Galaxy - III. Propelling reionisation with the faintest galaxies %U http://arxiv.org/abs/1403.6123 %X 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 (T_vir > 10^4 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 a significant fraction of the ionising photon budget because of their high number densities. We find that the galaxy luminosity function flattens above M_UV ~ -12 with a number density that is unchanged during reionisation. 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 $M/M_= 7.0-8.5$. We find that low-mass galaxies are just as efficient at producing ionising photons per unit mass as atomic cooling haloes. However, they are gradually photo-suppressed as they are engulfed in ionised regions, giving way for larger galaxies to dominate the latter half of reionisation. 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-alpha forest observations at z = 4-6. We find that haloes less massive than the atomic cooling limit provide nearly 30 per cent to the total ionising photon budget. Our work suggests that a yet-to-be observed population of low-mass galaxies was responsible for starting reionisation at very high redshifts.

@misc{wise2014birth, abstract = {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 (T_vir > 10^4 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 a significant fraction of the ionising photon budget because of their high number densities. We find that the galaxy luminosity function flattens above M_UV ~ -12 with a number density that is unchanged during reionisation. 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 $\log M/M_\odot = 7.0-8.5$. We find that low-mass galaxies are just as efficient at producing ionising photons per unit mass as atomic cooling haloes. However, they are gradually photo-suppressed as they are engulfed in ionised regions, giving way for larger galaxies to dominate the latter half of reionisation. 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-alpha forest observations at z = 4-6. We find that haloes less massive than the atomic cooling limit provide nearly 30 per cent to the total ionising photon budget. Our work suggests that a yet-to-be observed population of low-mass galaxies was responsible for starting reionisation at very high redshifts.}, added-at = {2014-03-26T09:53:25.000+0100}, author = {Wise, John H. and Demchenko, Vasiliy G. and Halicek, Martin T. and Norman, Michael L. and Turk, Matthew J. and Abel, Tom and Smith, Britton D.}, biburl = {https://www.bibsonomy.org/bibtex/27c286e04d72b260b264144c39aca9fc6/miki}, description = {[1403.6123] The Birth of a Galaxy - III. Propelling reionisation with the faintest galaxies}, interhash = {83e1263eeba5027cedc62be569a58aee}, intrahash = {7c286e04d72b260b264144c39aca9fc6}, keywords = {dwarf galaxy reionization}, note = {cite arxiv:1403.6123Comment: 21 pages, 15 figures, 4 tables. Submitted to MNRAS. Comments welcome}, timestamp = {2014-03-26T09:53:25.000+0100}, title = {The Birth of a Galaxy - III. Propelling reionisation with the faintest galaxies}, url = {http://arxiv.org/abs/1403.6123}, year = 2014 }