%0 Generic %1 watts2019beyond %A Watts, D. J. %A Addison, G. A. %A Bennett, C. L. %A Weiland, J. L. %D 2019 %K library %T Beyond optical depth: Future determination of ionization history from the CMB %U http://arxiv.org/abs/1910.00590 %X 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, $C_\ell^TE$, has roughly one quarter of the constraining power of $C_\ell^EE$ on the reionization optical depth $\tau$, and its addition improves the precision on $\tau$ by 20% over using $C_\ell^EE$ only. We also use a two-step reionization model with an additional high redshift step, parametrized by an early ionization fraction $x_e^min$, and a late reionization step at $z_re$. We find that future high signal-to-noise measurements of the multipoles $10łeqslant\ell<20$ are especially important for breaking the degeneracy between $x_e^min$ and $z_re$. In addition, we show that the uncertainties on these parameters determined from a map with sensitivity $10\,K\,arcmin$ 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.

@misc{watts2019beyond, abstract = {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 $10\leqslant\ell<20$ 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.}, added-at = {2019-10-03T06:17:10.000+0200}, author = {Watts, D. J. and Addison, G. A. and Bennett, C. L. and Weiland, J. L.}, biburl = {https://www.bibsonomy.org/bibtex/26845fff3e6766dc01750959e6ba0a582/gpkulkarni}, description = {Beyond optical depth: Future determination of ionization history from the CMB}, interhash = {7847484500ea215a807502d4b807e41d}, intrahash = {6845fff3e6766dc01750959e6ba0a582}, keywords = {library}, note = {cite arxiv:1910.00590Comment: 12 pages, 10 figures, submitted to ApJ}, timestamp = {2019-10-03T06:17:10.000+0200}, title = {Beyond optical depth: Future determination of ionization history from the CMB}, url = {http://arxiv.org/abs/1910.00590}, year = 2019 }