论文标题
在电离时期的21 cm-ksz-ksz bispectrum
The 21 cm-kSZ-kSZ Bispectrum during the Epoch of Reionization
论文作者
论文摘要
来自电离时代(EOR)的高红移21 cm信号是早期宇宙的有前途的观察探针。电流和下一代无线电干涉仪,例如电源阵列(HERA)和平方公里阵列(SKA)的氢时代,以测量EOR的21 cm自动功率谱。这个时代的另一个观察信号是宇宙微波背景(CMB)中的动力学Sunyaev-Zel'Dovich(KSZ)信号,即将到来的Simons天文台(SO)和CMB-S4实验将观察到这一点。 EOR的21 cm信号和对KSZ的贡献预计将是反相关的,前者来自乳层间培养基中中性气体的区域,后者来自电离区域。但是,由于电离区域同样有可能向观察者移动或离开观察者,因此KSZ和21 cm图之间的幼稚互相关遭受了发生的取消,因此与21 cm信号没有净相关性。我们在这里介绍了对21 cm-ksz-ksz Biseptrum的研究,该调查不应与简单的两点互相关的取消相同。我们表明,存在一个对电离历史敏感的重要且无易变的信号,这表明该统计量可用于确认或推断电离分数作为红移的函数。在没有前景污染的情况下,我们预测该信号与HERA的统计显着性高可检测到。我们研究的双光谱遭受了这样一个事实,即KSZ信号仅对具有长波长的视线组件的傅立叶模式敏感,这些模式通常由于前景污染而在21 cm数据集中丢失。我们讨论了减轻这种污染的可能策略,包括一个替代的四点统计量,可能有助于避免此问题。
The high-redshift 21 cm signal from the Epoch of Reionization (EoR) is a promising observational probe of the early universe. Current- and next-generation radio interferometers such as the Hydrogen Epoch of Reionization Array (HERA) and Square Kilometre Array (SKA) are projected to measure the 21 cm auto power spectrum from the EoR. Another observational signal of this era is the kinetic Sunyaev-Zel'dovich (kSZ) signal in the cosmic microwave background (CMB), which will be observed by the upcoming Simons Observatory (SO) and CMB-S4 experiments. The 21 cm signal and the contribution to the kSZ from the EoR are expected to be anti-correlated, the former coming from regions of neutral gas in the intergalactic medium and the latter coming from ionized regions. However, the naive cross-correlation between the kSZ and 21 cm maps suffers from a cancellation that occurs because ionized regions are equally likely to be moving toward or away from the observer and so there is no net correlation with the 21 cm signal. We present here an investigation of the 21 cm-kSZ-kSZ bispectrum, which should not suffer the same cancellation as the simple two-point cross-correlation. We show that there is a significant and non-vanishing signal that is sensitive to the reionization history, suggesting the statistic may be used to confirm or infer the ionization fraction as a function of redshift. In the absence of foreground contamination, we forecast that this signal is detectable at high statistical significance with HERA and SO. The bispectrum we study suffers from the fact that the kSZ signal is sensitive only to Fourier modes with long-wavelength line-of-sight components, which are generally lost in the 21 cm data sets owing to foreground contamination. We discuss possible strategies for alleviating this contamination, including an alternative four-point statistic that may help circumvent this issue.