发表机构
Stellenbosch University; University of Pennsylvania; University of Groningen（斯泰伦博斯大学; 宾夕法尼亚大学; 格罗宁根大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究利用kSZ²×21cm²互相关统计量，在z≈9–16探测再电离纪元，该统计量对IGM热演化与电离结构敏感，预测SKA-Low与CMB-HD组合信噪比约5.89，为高红移热历史提供互补约束。
AI 中文摘要
再电离纪元（EoR）的观测为理解首批发光源的性质和星系间介质（IGM）的热状态提供了关键见解。运动学苏尼亚耶夫-泽尔多维奇（kSZ）效应与中性氢（HI）21厘米辐射之间的互相关，为探测这一时代提供了有前景的手段，其对早期宇宙的电离历史和热历史均敏感。我们研究了在 $z\simeq9$--$16$ 范围内，平方 kSZ 场与平方 21厘米强度成图场（$\mathrm{kSZ}^{2}\times21\mathrm{cm}^{2}$）的互相关，重点关注 HI 自旋温度空间涨落的影响。这一高阶统计量避免了 kSZ 信号沿视线方向的抵消，而对 21厘米场进行平方运算则使得与成对相等且相反的高 $k_\parallel$ 模式（这些模式位于前景楔之外可观测）产生非零相关成为可能。我们预测了多种 21厘米和 CMB 实验组合的累积信噪比（$\mathrm{S/N}$），并考虑了实际的仪器噪声。对于基准加热历史和乐观的前景规避场景（$k_\parallel\leq0.1\\,h\\,\mathrm{Mpc}^{-1}$），我们发现 SKA-Low AA$^\ast\times$CMB-HD 的 $\mathrm{S/N}\simeq5.89$，HERA$\times$CMB-HD 的 $\mathrm{S/N}\simeq3.62$。如果前景楔延伸至地平线，这些值分别降至 $2.94$ 和 $2.85$。我们的结果表明，$\mathrm{kSZ}^{2}\times21\mathrm{cm}^{2}$ 对 IGM 的热演化及其电离结构均敏感，为高红移热历史和再电离历史提供了互补的约束。
英文摘要
Observations of the Epoch of Reionization (EoR) provide key insights into the nature of the first luminous sources and the thermal state of the intergalactic medium (IGM). Cross-correlations between the kinetic Sunyaev--Zel'dovich (kSZ) effect and neutral hydrogen (HI) 21-cm emission offer a promising probe of this era, sensitive to both the ionization and thermal histories of the early Universe. We investigate the cross-correlation of the squared kSZ field with the squared 21-cm intensity-mapping field ($\mathrm{kSZ}^{2}\times21\mathrm{cm}^{2}$) over $z\simeq9$--$16$, focusing on the impact of spatial fluctuations in the HI spin temperature. This higher-order statistic avoids line-of-sight cancellations in the kSZ signal, while squaring the 21-cm field enables non-vanishing correlations with pairs of equal and opposite high-$k_\parallel$ modes accessible outside the foreground wedge. We forecast the cumulative signal-to-noise ratio ($\mathrm{S/N}$) for several combinations of 21-cm and CMB experiments, including realistic instrumental noise. For a fiducial heating history and an optimistic foreground-avoidance scenario ($k_\parallel\leq0.1\,h\,\mathrm{Mpc}^{-1}$), we find $\mathrm{S/N}\simeq5.89$ for SKA-Low AA$^\ast\times$CMB-HD and $\simeq3.62$ for HERA$\times$CMB-HD. If the foreground wedge extends to the horizon, these decrease to $2.94$ and $2.85$, respectively. Our results demonstrate that $\mathrm{kSZ}^{2}\times21\mathrm{cm}^{2}$ is sensitive to the thermal evolution of the IGM as well as its ionization structure, providing complementary constraints on the high-redshift thermal and reionization histories.
Comments17 pages, 11 figures, 2 tables
