{"about":{"site":"https://codewithpapers.app","non_affiliation":"Code with Papers and Syntology are not affiliated with, endorsed by, or sponsored by Papers with Code, Meta, or the pwc-archive mirror.","licence":"CC BY-SA 4.0","licence_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","attribution":"https://codewithpapers.app/attribution","modified":"archive material modified by Syntology; see the attribution page"},"url":"/paper/beyond-optical-depth-future-determination-of","title":"Beyond optical depth: Future determination of ionization history from the CMB","arxiv_id":"1910.00590","date":"2019-10-01","proceeding":null,"authors":["D. J. Watts","G. E. Addison","C. L. Bennett","J. L. Weiland"],"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.","url_abs":"https://arxiv.org/abs/1910.00590v2","url_pdf":"https://arxiv.org/pdf/1910.00590v2.pdf","source":{"archive":"pwc-archive (Hugging Face), CC BY-SA 4.0","snapshot":"2025-07-28","licence_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","row_kind":"links_only","authors_date_abstract":"arXiv metadata, CC0 1.0 (https://info.arxiv.org/help/license), from the Kaggle arXiv metadata snapshot of 2026-09-12"},"code_links":[{"paper_slug":"beyond-optical-depth-future-determination-of","repo_url":"https://github.com/dncnwtts/low-ell-reionization","is_official":1,"mentioned_in_paper":0,"mentioned_in_github":1,"framework":"none","reach":null},{"paper_slug":"beyond-optical-depth-future-determination-of","repo_url":"https://github.com/pqrs6/low-ell-reionization","is_official":0,"mentioned_in_paper":0,"mentioned_in_github":1,"framework":"none","reach":null}],"tasks":[],"methods":[],"datasets_introduced":[],"methods_introduced":[],"results":[],"syntology":{"atlas_url":null,"mcp":null,"developers":"https://syntology.ai/developers"},"arxiv_metadata":null,"syntology_extracted_results":null}