论文标题
使用$ 150 \，{\ rm MHz} $ gmrt观测值演示宇宙学HI 21-CM功率谱的锥形网格估计器（TGE）
Demonstrating the Tapered Gridded Estimator (TGE) for the Cosmological HI 21-cm Power Spectrum using $150 \, {\rm MHz}$ GMRT observations
论文作者
论文摘要
我们将锥形网格估计量（TGE）应用于从$ 150 \，{\ rm MHz} $ gmrt观测值估算宇宙学21厘米的功率谱，，{\ rm MHz} $ gmrt观测值，该观测值与Redshift $ z = 8.28 $的中性氢（HI）相对应。这里使用TGE来测量多频角功率谱（MAPS）$ c _ {\ ell}（Δν）$首先，我们从中估算21厘米功率谱$ p（k _ {\ perp}，k _ {\ parallel}）$。此处的数据太小了，无法检测到，目的是证明估算器的功能。我们发现估计的功率谱与预期的前景和噪声行为一致。这表明该估计器正确估计了噪声偏差，并减去了这一点，以产生对功率谱的无偏估计。由于射频干扰，必须将超过$ 47 \％的频率通道从数据中丢弃，但是，由于缺失的通道，估计的功率谱并未显示任何伪像。最后，我们表明，可以通过从相位中心的大角度分离处逐渐减少天空响应来抑制前景的贡献。我们将“ eor窗口”中矩形区域内的k模式结合在一起，以获取球形bin的平均无量纲功率谱$δ^{2}（k）$以及与所测得的$δ^{2}（k）$相关的统计误差$σ$。最低$ k $ -bin产生$δ^{2}（k）=（61.47）^{2} \，{\ rm k}^{2} $ at $ k = 1.59 \，\，\ textrm {mpc} k}^{2} $。我们获得$ 2 \，σ$上限的$（72.66）^{2} \，\ textrm {k}^{2} $上的均方根HI 21厘米亮度温度在$ k = 1.59 \，\，\，\ textrm {mpc}^{ - 1} $。
We apply the Tapered Gridded Estimator (TGE) for estimating the cosmological 21-cm power spectrum from $150 \, {\rm MHz}$ GMRT observations which corresponds to the neutral hydrogen (HI) at redshift $z = 8.28$. Here TGE is used to measure the Multi-frequency Angular Power Spectrum (MAPS) $C_{\ell}(Δν)$ first, from which we estimate the 21-cm power spectrum $P(k_{\perp},k_{\parallel})$. The data here are much too small for a detection, and the aim is to demonstrate the capabilities of the estimator. We find that the estimated power spectrum is consistent with the expected foreground and noise behaviour. This demonstrates that this estimator correctly estimates the noise bias and subtracts this out to yield an unbiased estimate of the power spectrum. More than $47\%$ of the frequency channels had to be discarded from the data owing to radio-frequency interference, however the estimated power spectrum does not show any artifacts due to missing channels. Finally, we show that it is possible to suppress the foreground contribution by tapering the sky response at large angular separations from the phase center. We combine the k modes within a rectangular region in the `EoR window' to obtain the spherically binned averaged dimensionless power spectra $Δ^{2}(k)$ along with the statistical error $σ$ associated with the measured $Δ^{2}(k)$. The lowest $k$-bin yields $Δ^{2}(k)=(61.47)^{2}\,{\rm K}^{2}$ at $k=1.59\,\textrm{Mpc}^{-1}$, with $σ=(27.40)^{2} \, {\rm K}^{2}$. We obtain a $2 \, σ$ upper limit of $(72.66)^{2}\,\textrm{K}^{2}$ on the mean squared HI 21-cm brightness temperature fluctuations at $k=1.59\,\textrm{Mpc}^{-1}$.
