NEW LIMITS ON 21 cm EPOCH OF REIONIZATION FROM PAPER-32 CONSISTENT WITH AN X-RAY HEATED INTERGALACTIC MEDIUM AT z = 7.7
NEW LIMITS ON 21 cm EPOCH OF REIONIZATION FROM PAPER-32 CONSISTENT WITH AN X-RAY HEATED INTERGALACTIC MEDIUM AT z = 7.7
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DOI：
10.1088/0004-637x/788/2/106
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
A. Parsons;Adrian Liu;J. Aguirre;Z. Ali;R. Bradley;C. Carilli;D. DeBoer;M. Dexter;N. Gugliucci-N.-G
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文献类型：
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作者：
A. Parsons;Adrian Liu;J. Aguirre;Z. Ali;R. Bradley;C. Carilli;D. DeBoer;M. Dexter;N. Gugliucci-N.-G
我们提出了对21厘米再电离历元（EoR）功率谱的新约束，该功率谱来自于三个月的观测，这些观测来自于使用32天线，Donald C. Backer精密阵列探测南非再电离历元的双极化部署。在本文中，我们证明了延迟谱方法在避免前景方面的有效性，实现了超过8个数量级的前景抑制（在mK2中）。将这种方法与去除仪器系统产生的非对角线协方差的过程相结合，我们在z = 7.7时，k = 0.27 h Mpc−1的最佳2σ上限为（41 mK）2。这个极限落在预期21厘米EoR信号水平的明亮预测的一个数量级内。利用这些测量设定的上限，我们对各种再电离模型的中性区21 cm发射的亮度温度产生了新的约束。我们表明，在几种电离情况下，我们的测量结果与冷再电离不一致。也就是说，中性星系间介质（IGM）的加热是必要的，以保持与我们报告的约束一致。因此，我们有证据表明，到z = 7.7时，黑洞已经从原始的寒冷状态变暖了，这可能是由来自高质量x射线双星或小类星体的x射线引起的。这一证据的强度取决于IGM的电离状态，这是我们还无法限制的。这一结果与再电离如何进行的标准预测是一致的。
We present new constraints on the 21 cm Epoch of Reionization (EoR) power spectrum derived from three months of observing with a 32 antenna, dual-polarization deployment of the Donald C. Backer Precision Array for Probing the Epoch of Reionization in South Africa. In this paper, we demonstrate the efficacy of the delay-spectrum approach to avoiding foregrounds, achieving over eight orders of magnitude of foreground suppression (in mK2). Combining this approach with a procedure for removing off-diagonal covariances arising from instrumental systematics, we achieve a best 2σ upper limit of (41 mK)2 for k = 0.27 h Mpc−1 at z = 7.7. This limit falls within an order of magnitude of the brighter predictions of the expected 21 cm EoR signal level. Using the upper limits set by these measurements, we generate new constraints on the brightness temperature of 21 cm emission in neutral regions for various reionization models. We show that for several ionization scenarios, our measurements are inconsistent with cold reionization. That is, heating of the neutral intergalactic medium (IGM) is necessary to remain consistent with the constraints we report. Hence, we have suggestive evidence that by z = 7.7, the H i has been warmed from its cold primordial state, probably by X-rays from high-mass X-ray binaries or miniquasars. The strength of this evidence depends on the ionization state of the IGM, which we are not yet able to constrain. This result is consistent with standard predictions for how reionization might have proceeded.