论文标题
在宇宙黎明时绘制离散星系，观察21厘米
Mapping discrete galaxies at cosmic dawn with 21-centimeter observations
论文作者
论文摘要
在宇宙黎明时，来自半阶层氢的21厘米信号是由一些最早的恒星驱动的，由Lyman-$α$光子驱动，产生了当时反映星系分布的空间模式。由于前景较大，人们认为在红移20周围，只有在统计上检测21厘米波动才能可行，从而产生了早期星系的有限的间接探针。在这里，我们表明，宇宙黎明的21厘米图像实际上应由大型（数十张巨型甲壳虫）主导，围绕各个星系的高对比度气泡。我们使用实质上升级的半数字模拟代码来证明这一点，该代码实际上捕获了这个时代预期的小星系的形成和21厘米效应。与早期星系稀有性相关的少量统计数据，再加上Lyman-$α$系列蓝色翼的光子的多重散射，创建大气泡，并使21厘米的功率谱增加2--7，并添加到它的特征，以测量星系的典型明亮性。即使在计划的实验（例如平方公里阵列或氢气时期），即使在暗物质光环中形成的，质量低至$ 10^8 \，m_ \ odot $，也比乳halo小halo小，这些早期星系的各种特征可能可以通过计划的实验（例如平方公里阵列或回离阵列的氢时代）来检测到。
At cosmic dawn, the 21-centimeter signal from intergalactic hydrogen was driven by Lyman-$α$ photons from some of the earliest stars, producing a spatial pattern that reflected the distribution of galaxies at that time. Due to the large foreground, it is thought that around redshift 20 it is only observationally feasible to detect 21-cm fluctuations statistically, yielding a limited, indirect probe of early galaxies. Here we show that 21-cm images at cosmic dawn should actually be dominated by large (tens of comoving megaparsecs), high contrast bubbles surrounding individual galaxies. We demonstrate this using a substantially upgraded semi-numerical simulation code that realistically captures the formation and 21-cm effects of the small galaxies expected during this era. Small number statistics associated with the rarity of early galaxies, combined with the multiple scattering of photons in the blue wing of the Lyman-$α$ line, create the large bubbles and also enhance the 21-cm power spectrum by a factor of 2--7 and add to it a feature that measures the typical brightness of galaxies. These various signatures of discrete early galaxies are potentially detectable with planned experiments such as the Square Kilometer Array or the Hydrogen Epoch of Reionization Array, even if the early stars formed in dark matter halos with masses as low as $10^8\, M_\odot$, ten thousand times smaller than the Milky Way halo.
