%0 Generic %1 kimm2014escape %A Kimm, Taysun %A Cen, Renyue %D 2014 %K escape fraction reionisation reionization %T Escape fraction of ionizing photons during reionization: effects due to supernova feedback and runaway OB stars %U http://arxiv.org/abs/1405.0552 %X The fraction of hydrogen ionizing photons escaping from galaxies into the intergalactic medium is a critical ingredient in the theory of reionization. We use two zoomed-in, high-resolution (4 pc), cosmological radiation hydrodynamic simulations with adaptive mesh refinement to investigate the impact of two physical mechanisms (supernova feedback and runaway OB stars) on the escape fraction (f_esc) at the epoch of reionization (z>7). We implement a new, physically motivated supernova feedback model that can approximate the Sedov solutions at all (from the free expansion to snowplow) stages. We find that there is a significant time delay of about ten million years between the peak of star formation and that of escape fraction, due to the time required for the build-up and subsequent destruction of the star-forming cloud by supernova feedback. Consequently, the photon number-weighted mean escape fraction for dwarf galaxies in halos of mass 10^8-10^10.5 Msun is found to be <fesc>~11%, although instantaneous values of f_esc>20% are common when star formation is strongly modulated by the supernova explosions. We find that the inclusion of runaway OB stars increases the mean escape fraction by 22% to <fesc>~14%. As supernovae resulting from runaway OB stars tend to occur in less dense environments, the feedback effect is enhanced and star formation is further suppressed in halos with Mvir>10^9 Msun in the simulation with runaway OB stars compared with the model without them. While both our models produce enough ionizing photons to maintain a fully ionized universe at z>7 as observed, a still higher amount of ionizing photons at z>9 appears necessary to accommodate the high observed electron optical depth inferred from cosmic microwave background observations.

@misc{kimm2014escape, abstract = {The fraction of hydrogen ionizing photons escaping from galaxies into the intergalactic medium is a critical ingredient in the theory of reionization. We use two zoomed-in, high-resolution (4 pc), cosmological radiation hydrodynamic simulations with adaptive mesh refinement to investigate the impact of two physical mechanisms (supernova feedback and runaway OB stars) on the escape fraction (f_esc) at the epoch of reionization (z>7). We implement a new, physically motivated supernova feedback model that can approximate the Sedov solutions at all (from the free expansion to snowplow) stages. We find that there is a significant time delay of about ten million years between the peak of star formation and that of escape fraction, due to the time required for the build-up and subsequent destruction of the star-forming cloud by supernova feedback. Consequently, the photon number-weighted mean escape fraction for dwarf galaxies in halos of mass 10^8-10^10.5 Msun is found to be <fesc>~11%, although instantaneous values of f_esc>20% are common when star formation is strongly modulated by the supernova explosions. We find that the inclusion of runaway OB stars increases the mean escape fraction by 22% to <fesc>~14%. As supernovae resulting from runaway OB stars tend to occur in less dense environments, the feedback effect is enhanced and star formation is further suppressed in halos with Mvir>10^9 Msun in the simulation with runaway OB stars compared with the model without them. While both our models produce enough ionizing photons to maintain a fully ionized universe at z>7 as observed, a still higher amount of ionizing photons at z>9 appears necessary to accommodate the high observed electron optical depth inferred from cosmic microwave background observations.}, added-at = {2014-05-06T10:03:00.000+0200}, author = {Kimm, Taysun and Cen, Renyue}, biburl = {https://www.bibsonomy.org/bibtex/26bc173a29f968833c05a9517bbca1e1d/miki}, description = {[1405.0552] Escape fraction of ionizing photons during reionization: effects due to supernova feedback and runaway OB stars}, interhash = {2a13813f6768a73dbbe0cc36a596550c}, intrahash = {6bc173a29f968833c05a9517bbca1e1d}, keywords = {escape fraction reionisation reionization}, note = {cite arxiv:1405.0552Comment: 18 pages, 18 figures, 2 tables. Accepted for publication in ApJ}, timestamp = {2014-05-06T10:03:00.000+0200}, title = {Escape fraction of ionizing photons during reionization: effects due to supernova feedback and runaway OB stars}, url = {http://arxiv.org/abs/1405.0552}, year = 2014 }