Feasibility of the Alcock Paczynski (AP) test by stacking voids in the 21cm line intensity field is presented. We analyze the Illstris-TNG simulation to obtain the 21cm signal map. We then randomly distribute particles depending on the 21cm intensity field to find voids by using publicly available code, VIDE. As in the galaxy clustering, the shape of the stacked void in the 21cm field is squashed along the line of sight due to the peculiar velocities in redshift-space, although it becomes spherical in real-space. The redshift-space distortion for the stacked void weakly depends on redshift and we show that the dependency can be well described by the linear prediction, with the amplitude of the offset being free parameters. We find that the AP test using the stacked voids in a 21cm intensity map is feasible and the parameter estimation on $\Omega_{\rm m}$ and $w$ is unbiased.

中文翻译：

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Alcock Paczynski 测试，在 21cm 强度场中有空隙

展示了通过在 21 厘米线强度场中堆叠空隙进行 Alcock Paczynski (AP) 测试的可行性。我们分析了 Illstris-TNG 模拟以获得 21cm 信号图。然后，我们根据 21 厘米强度场随机分布粒子，以使用公开可用的代码 VIDE 找到空隙。就像在星系团中一样，21cm 场中的堆叠空隙的形状由于红移空间中的特殊速度而沿视线被挤压，尽管它在现实空间中变成了球面。 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 堆叠空隙的红移空间失真弱依赖于红移，我们表明线性预测可以很好地描述这种依赖性，偏移的幅度是自由参数。