arXiv 2102.009752021-02astro-ph.COastro-ph.GA

用首次测量CMB光学深度起伏和康普顿y映象之间的互相关来约束再电离

Constraining reionization with the first measurement of the cross-correlation between the CMB optical-depth fluctuations and the Compton y-map

Toshiya Namikawa, Anirban Roy, Blake D. Sherwin, Nicholas Battaglia, David N. Spergel

备注：: 13 pages, 9 figures, Accepted for publication in PRD
发表信息：: Phys. Rev. D 104, 063514 (2021)
DOI：: 10.1103/PhysRevD.104.063514

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摘要：

我们提出了一个新的再电离探针，使用宇宙微波背景（CMB）的观测;在CMB光学深度的波动，探测积分电子密度，$δτ$，和康普顿$y$ -地图探测积分电子压力之间的互相关。这种互相关比$y$图功率谱受到后期集群贡献的污染要少得多。此外，这种互相关可以抑制电离气泡的温度，而光学深度涨落和动力学SZ效应则不能。我们测量这个新的观测使用普朗克$y$地图以及地图的光学深度波动，我们从普朗克CMB温度数据重建。我们使用我们的测量，以获得第一个CMB的上限内的电离气泡，$T_{\rm b}\lesssim 7.0\times10^5\,$ K（$2\,σ$）的温度。我们还提出了未来的预测，假设一个基准模型的特征再电离气泡大小$R_{\rm b}=5\,$ Mpc和$T_{\rm b}=5\times10^4\,$ K。使用信号主导的类PICO $y$图的基准互相关的信噪比变为具有CMB-S4 $δτ$的$\simeq7$和具有CMB-HD $δτ$的$\simeq13$。对于基准模型，我们预测CMB-HD $-$ PICO互相关应实现再电离参数的精确测量; $T_{\rm b}\simeq 49800^{+4500}_{-5100}\,$ K和$R_{\rm b}\simeq 5.09^{+0.66}_{-0.79}\,$ Mpc。由于电子密度波动的功率谱受$δτ$自动谱的约束，温度约束应该仅弱模型依赖于电子分布的细节，并且应该在统计上代表再电离期间电离气泡中的温度。因此，这种互相关可能成为未来CMB实验的重要观察指标。

英文摘要：

We propose a new reionization probe that uses cosmic microwave background (CMB) observations; the cross-correlation between fluctuations in the CMB optical depth which probes the integrated electron density, $δτ$, and the Compton $y$-map which probes the integrated electron pressure. This cross-correlation is much less contaminated than the $y$-map power spectrum by late-time cluster contributions. In addition, this cross-correlation can constrain the temperature of ionized bubbles while the optical-depth fluctuations and kinetic SZ effect can not. We measure this new observable using a Planck $y$-map as well as a map of optical-depth fluctuations that we reconstruct from Planck CMB temperature data. We use our measurements to derive a first CMB-only upper limit on the temperature inside ionized bubbles, $T_{\rm b}\lesssim 7.0\times10^5\,$K ($2\,σ$). We also present future forecasts, assuming a fiducial model with characteristic reionization bubble size $R_{\rm b}=5\,$Mpc and $T_{\rm b}=5\times10^4\,$K. The signal-to-noise ratio of the fiducial cross-correlation using a signal dominated PICO-like $y$-map becomes $\simeq7$ with CMB-S4 $δτ$ and $\simeq13$ with CMB-HD $δτ$. For the fiducial model, we predict that the CMB-HD $-$ PICO cross-correlation should achieve an accurate measurement of the reionization parameters; $T_{\rm b}\simeq 49800^{+4500}_{-5100}\,$K and $R_{\rm b}\simeq 5.09^{+0.66}_{-0.79}\,$Mpc. Since the power spectrum of the electron density fluctuations is constrained by the $δτ$ auto spectrum, the temperature constraints should be only weakly model-dependent on the details of the electron distributions and should be statistically representative of the temperature in ionized bubbles during reionization. This cross-correlation could, therefore, become an important observable for future CMB experiments.

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