论文标题
从$ z = 9.1 $的多余无线电背景上的严格约束从lofar
Tight Constraints on the Excess Radio Background at $z = 9.1$ from LOFAR
论文作者
论文摘要
在低无线电频率下，Arcade2和LWA1实验声称超过宇宙微波背景（CMB）。如果在1.42 GHz时，宇宙学的高红移贡献在CMB的0.1％至22％之间，则可以解释中性氢的21 cm信号中的暂定边缘低波段检测。我们根据141小时与Lofar的观察结果对21 cm信号的上限（$ z = 9.1 $）使用，以评估高红移宇宙对检测到的无线电背景的贡献。在恒星形成光环的天体物理特性上边缘化，我们发现（95％C.L.）宇宙射电背景最多可以是CMB的9.6％，为1.42 GHz。该限制排除了高红移宇宙对Arcade2和LWA1测量值的贡献。尽管Lofar的位置限制了额外的无线电背景，但仍然允许比CMB（1.42 GHz）的0.1-9.6美元超过$ 0.1-9.6 $％，并且可以解释边缘低频检测。我们还将气体的热和电离状态限制为$ z = 9.1 $，并限制了第一个恒星形成对象的性质。我们发现，与边缘高频数据的限制一致，Lofar数据以X射线效率低下的情况和宇宙仅在大量晕圈中被恒星电离的情况来限制场景。
The ARCADE2 and LWA1 experiments have claimed an excess over the Cosmic Microwave Background (CMB) at low radio frequencies. If the cosmological high-redshift contribution to this radio background is between 0.1% and 22% of the CMB at 1.42 GHz, it could explain the tentative EDGES Low-Band detection of the anomalously deep absorption in the 21-cm signal of neutral hydrogen. We use the upper limit on the 21-cm signal from the Epoch of Reionization ($z=9.1$) based on 141 hours of observations with LOFAR to evaluate the contribution of the high redshift Universe to the detected radio background. Marginalizing over astrophysical properties of star-forming halos, we find (at 95% C.L.) that the cosmological radio background can be at most 9.6% of the CMB at 1.42 GHz. This limit rules out strong contribution of the high-redshift Universe to the ARCADE2 and LWA1 measurements. Even though LOFAR places limit on the extra radio background, excess of $0.1-9.6$% over the CMB (at 1.42 GHz) is still allowed and could explain the EDGES Low-Band detection. We also constrain the thermal and ionization state of the gas at $z = 9.1$ and put limits on the properties of the first star-forming objects. We find that, in agreement with the limits from EDGES High-Band data, LOFAR data constrain scenarios with inefficient X-ray sources and cases where the Universe was ionized by stars in massive halos only.
