再电离时期电离光子的逃逸分数:平方公里阵列的可观测性
The Escape Fraction of Ionizing Photons During the Epoch of Reionization: observability with the Square Kilometre Array
摘要:
电离光子的逃逸分数$f_\mathrm{esc}$是表征再电离时期的重要参数之一,它在观测和理论上都是不受约束的。最近的工作强调了星系尺度反馈对$f_\mathrm{esc}$瞬时值的影响,因此开发一个再电离自洽耦合到星系演化的模型非常重要。在这项工作中,我们提出了这样一个模型,并探讨如何物理动机的功能形式的$f_\mathrm{esc}$影响星系际介质内的电离氢的演变。使用的$21$厘米功率谱的演变,我们调查的可能性观测区分恒定的$f_\mathrm{esc}$和其他模型,依赖于不同形式的星系反馈。我们发现,改变潜在的$f_\mathrm{esc}$和星系反馈之间的联系,大大改变了大规模的$21$厘米功率。即将推出的平方公里阵列低频仪器具有在固定光学深度区分我们的模型的灵敏度,只需要$200$小时的积分时间集中在红移$z = 7.5-8.5$。将这些结果推广到不同的光学深度将需要多个$800$小时的观测跨越红移$z = 7-10$。这提供了一个令人兴奋的机会,以观测约束最难以捉摸的参数之一,在时代的再电离。
英文摘要:
One of the most important parameters in characterizing the Epoch of Reionization, the escape fraction of ionizing photons, $f_\mathrm{esc}$, remains unconstrained both observationally and theoretically. With recent work highlighting the impact of galaxy-scale feedback on the instantaneous value of $f_\mathrm{esc}$, it is important to develop a model in which reionization is self-consistently coupled to galaxy evolution. In this work, we present such a model and explore how physically motivated functional forms of $f_\mathrm{esc}$ affect the evolution of ionized hydrogen within the intergalactic medium. Using the $21$cm power spectrum evolution, we investigate the likelihood of observationally distinguishing between a constant $f_\mathrm{esc}$ and other models that depend upon different forms of galaxy feedback. We find that changing the underlying connection between $f_\mathrm{esc}$ and galaxy feedback drastically alters the large-scale $21$cm power. The upcoming Square Kilometre Array Low Frequency instrument possesses the sensitivity to differentiate between our models at a fixed optical depth, requiring only $200$ hours of integration time focused on redshifts $z = 7.5-8.5$. Generalizing these results to account for a varying optical depth will require multiple $800$ hour observations spanning redshifts $z = 7-10$. This presents an exciting opportunity to observationally constrain one of the most elusive parameters during the Epoch of Reionization.
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