{"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/prospects-for-rm-ksz-2-rm-21cm-2-cross","title":"Prospects for ${\\rm kSZ^2}$-${\\rm 21cm^2}$ Cross-Correlations during Reionization","arxiv_id":"2503.09462","date":"2025-03-12","proceeding":null,"authors":["Meng Zhou","Paul La Plante","Adam Lidz","Yi Mao","Yin-Zhe Ma"],"abstract":"The 21\\,cm line and the patchy kinetic Sunyaev-Zel'dovich (kSZ) effect are promising and complementary probes of the Epoch of Reionization (EoR). A challenge for cross-correlating these two signals is that foreground avoidance or removal algorithms applied to the 21\\,cm data inevitably sacrifice Fourier modes with long wavelengths along the line-of-sight (i.e., low-$k_\\parallel$ modes), yet \\textit{only} these same modes contribute to the kSZ signal. Here we show that a suitable kSZ$^2$ $\\times$ 21\\,cm$^2$ cross-correlation statistic nevertheless remains non-vanishing, even after filtering out the corrupted low-$k_\\parallel$ Fourier modes from the 21\\,cm data. We simulate the kSZ$^2$ $\\times$ 21\\,cm$^2$ cross-correlation signal across reionization-era redshifts and find distinctive redshift evolution. This signal peaks early in the reionization history, when the volume-averaged fraction is around $0.1 \\lesssim x_\\mathrm{HII} \\lesssim 0.2$, after which it changes sign and reaches a minimum near reionization's midpoint ($x_\\mathrm{HII} \\sim 0.5$), while the signal gradually vanishes as reionization completes. These trends appear generic across three simulated models which differ in their reionization histories. We forecast the detectability of the kSZ$^2$ $\\times$ 21\\,cm$^2$ cross-power spectrum for the HERA and SKA1-Low 21\\,cm experiments in combination with current and next-generation CMB surveys including the Simons Observatory, CMB-S4, and CMB-HD. We find that a high-significance detection ($\\mathrm{S/N} \\gtrsim 5\\sigma$) is possible with SKA1-Low and CMB-S4.","url_abs":"https://arxiv.org/abs/2503.09462v1","url_pdf":"https://arxiv.org/pdf/2503.09462v1.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":"prospects-for-rm-ksz-2-rm-21cm-2-cross","repo_url":"https://github.com/21cmfast/21cmFAST","is_official":1,"mentioned_in_paper":0,"mentioned_in_github":0,"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}