Beyond optical depth: Future determination of ionization history from the CMB. (arXiv:1910.00590v1 [astro-ph.CO])
<a href="http://arxiv.org/find/astro-ph/1/au:+Watts_D/0/1/0/all/0/1">D. J. Watts</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Addison_G/0/1/0/all/0/1">G. A. Addison</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bennett_C/0/1/0/all/0/1">C. L. Bennett</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Weiland_J/0/1/0/all/0/1">J. L. Weiland</a>
We explore the fundamental limits to which reionization histories can be
constrained using only large-scale cosmic microwave background (CMB) anisotropy
measurements. The redshift distribution of the fractional ionization $x_e(z)$
affects the angular distribution of CMB polarization. We project constraints on
the reionization history of the universe using low-noise full-sky temperature
and E-mode measurements of the CMB. We show that the measured TE power
spectrum, $hat C_ell^mathrm{TE}$, has roughly one quarter of the
constraining power of $hat C_ell^mathrm{EE}$ on the reionization optical
depth $tau$, and its addition improves the precision on $tau$ by 20% over
using $hat C_ell^mathrm{EE}$ only. We also use a two-step reionization model
with an additional high redshift step, parametrized by an early ionization
fraction $x_e^mathrm{min}$, and a late reionization step at $z_mathrm{re}$.
We find that future high signal-to-noise measurements of the multipoles
$10leqslantell<20$ are especially important for breaking the degeneracy
between $x_e^mathrm{min}$ and $z_mathrm{re}$. In addition, we show that the
uncertainties on these parameters determined from a map with sensitivity
$10,mathrm{mu K,arcmin}$ are less than 5% larger than the uncertainties in
the noiseless case, making this noise level a natural target for future large
sky area E-mode measurements.
We explore the fundamental limits to which reionization histories can be
constrained using only large-scale cosmic microwave background (CMB) anisotropy
measurements. The redshift distribution of the fractional ionization $x_e(z)$
affects the angular distribution of CMB polarization. We project constraints on
the reionization history of the universe using low-noise full-sky temperature
and E-mode measurements of the CMB. We show that the measured TE power
spectrum, $hat C_ell^mathrm{TE}$, has roughly one quarter of the
constraining power of $hat C_ell^mathrm{EE}$ on the reionization optical
depth $tau$, and its addition improves the precision on $tau$ by 20% over
using $hat C_ell^mathrm{EE}$ only. We also use a two-step reionization model
with an additional high redshift step, parametrized by an early ionization
fraction $x_e^mathrm{min}$, and a late reionization step at $z_mathrm{re}$.
We find that future high signal-to-noise measurements of the multipoles
$10leqslantell<20$ are especially important for breaking the degeneracy
between $x_e^mathrm{min}$ and $z_mathrm{re}$. In addition, we show that the
uncertainties on these parameters determined from a map with sensitivity
$10,mathrm{mu K,arcmin}$ are less than 5% larger than the uncertainties in
the noiseless case, making this noise level a natural target for future large
sky area E-mode measurements.
http://arxiv.org/icons/sfx.gif
