论文标题
AARTFAAC宇宙探索器：边缘吸收槽中21 cm功率谱的观察
The AARTFAAC Cosmic Explorer: observations of the 21-cm power spectrum in the EDGES absorption trough
论文作者
论文摘要
边缘协作报道的21-CM吸收特征比传统天体物理模型预测的功能强几倍。如果是真正的，则更深的吸收可能会导致21 cm信号在度尺度上（RMS中最多1〜开尔文）上的波动更强，从而使这些波动在与以前的预测相比近50〜倍的整合时间中可检测到。我们开始采用Aartfaac宽田图像仪的“ Aartfaac宇宙探险家”（ACE）程序，以测量或设置限制21厘米波动$ z = 17.9-9-18.6 $（$δν= 72.36-75.09 $ 〜mhz）在Redshift范围内的功率谱，对应量均得到了启用。在这里，我们从两个LST垃圾箱中介绍了第一个结果：23.5-23.75h和23.5-23.75h，每个数据都有2个数据，记录在“半漂移扫描”模式下。我们演示了在AARTFAAC数据上的新ACE数据处理管道（根据Lofar-eor管道改编）的应用。我们观察到频道的噪声估计以及时间差异的stokes〜$ v $可见性彼此一致。在整合和减去明亮前景的2 h之后，我们在21厘米的功率谱上获得了$2σ$上限，$δ_{21}}^2 <（8139〜 \ textrm {mk}）^2 $和$δ__{21}}}} 0.144〜h \，\ textrm {cmpc}^{ - 1} $用于两个LST垃圾箱。对于两个LST垃圾箱的噪声偏差校正的功率谱图，产生的上限为$δ_{21}^2 <（7388〜 \ textrm {Mk}）^2 $ at $ k = 0.144〜h \，\ h \，\ textrm {cmpc}^^{-1} $。这些是迄今为止这些红移的最深上限。
The 21-cm absorption feature reported by the EDGES collaboration is several times stronger than that predicted by traditional astrophysical models. If genuine, a deeper absorption may lead to stronger fluctuations on the 21-cm signal on degree scales (up to 1~Kelvin in rms), allowing these fluctuations to be detectable in nearly 50~times shorter integration times compared to previous predictions. We commenced the "AARTFAAC Cosmic Explorer" (ACE) program, that employs the AARTFAAC wide-field imager, to measure or set limits on the power spectrum of the 21-cm fluctuations in the redshift range $z = 17.9-18.6$ ($Δν= 72.36-75.09$~MHz) corresponding to the deep part of the EDGES absorption feature. Here, we present first results from two LST bins: 23.5-23.75h and 23.5-23.75h, each with 2~h of data, recorded in `semi drift-scan' mode. We demonstrate the application of the new ACE data-processing pipeline (adapted from the LOFAR-EoR pipeline) on the AARTFAAC data. We observe that noise estimates from the channel and time-differenced Stokes~$V$ visibilities agree with each other. After 2~h of integration and subtraction of bright foregrounds, we obtain $2σ$ upper limits on the 21-cm power spectrum of $Δ_{21}^2 < (8139~\textrm{mK})^2$ and $Δ_{21}^2 < (8549~\textrm{mK})^2$ at $k = 0.144~h\,\textrm{cMpc}^{-1}$ for the two LST bins. Incoherently averaging the noise bias-corrected power spectra for the two LST bins yields an upper limit of $Δ_{21}^2 < (7388~\textrm{mK})^2$ at $k = 0.144~h\,\textrm{cMpc}^{-1}$. These are the deepest upper limits thus far at these redshifts.
