Escape fraction of ionizing photons during reionization: effects due to
supernova feedback and runaway OB stars
T. Kimm, and R. Cen. (2014)cite arxiv:1405.0552Comment: 18 pages, 18 figures, 2 tables. Accepted for publication in ApJ.
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.
Description
[1405.0552] Escape fraction of ionizing photons during reionization: effects due to supernova feedback and runaway OB stars
%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
}