论文标题
优化21厘米观测星系观察的光谱堆叠：准确性评估和对称堆叠
Optimizing spectral stacking for 21-cm observations of galaxies: accuracy assessment and symmetrized stacking
论文作者
论文摘要
我们介绍了以$ 21 $ -CM光谱线堆叠实验进行的普通操作的准确性的评估。为此，我们生成模拟干涉数据，以$ 1310 <ν<1420 $ MHz（$ 0.005 <z <0.084 $）以$ 1310 <ν<1420 $ \ sim 6 $ \ sim 6 $ deg $^2 $模仿真实Meerkat的观察性特征。 We find that the primary beam correction accounts for just few per cent ($\sim8\%$ at 0 primary beam power, $\sim 3\%$ at 0.6 primary beam power) deviations from the true $M_{\rm HI}$ signal, and that weighting schemes based on noise properties provide unbiased results.相反，将基于距离的加权方案应用于磁通量限制的样本（$ΔM_ {\ rm hi} \ sim 40-50 \％$ $）。我们发现在堆叠过程中考虑光谱红移不确定性时，获得的最终$ \ braket {m _ {\ rm hi}} $（$Δz\ sim 0.00035 $，即$δV\ sim 100 \，sim 100 \，{我们还提出了一种新型技术，可以通过利用星系群的几何对称性来增加星系样品的有效尺寸，从而在分析最终堆叠频谱（Cube en中的一个因子4）时，可能会通过因子$ \ sim \ sqrt {2} $来增强SNR。发现此过程是坚定的，同时如预期的那样有效地增加了SNR。我们认为，采用详细且现实的模拟需要一个适当的框架来以准确可靠的方式从SKA Pathfinders中利用即将到来的数据集。
We present an assessment of the accuracy of common operations performed in $21$-cm spectral line stacking experiments. To this end, we generate mock interferometric data surveying the 21-cm emission at frequency $1310<ν<1420$ MHz ($0.005<z<0.084$) and covering an area $\sim 6$ deg$^2$ of the sky, mimicking the observational characteristics of real MeerKAT observations. We find that the primary beam correction accounts for just few per cent ($\sim8\%$ at 0 primary beam power, $\sim 3\%$ at 0.6 primary beam power) deviations from the true $M_{\rm HI}$ signal, and that weighting schemes based on noise properties provide unbiased results. On the contrary, weighting schemes based on distance can account for significant systematic mass differences when applied to a flux-limited sample ($ΔM_{\rm HI}\sim 40-50\%$ in the studied case). We find no significant difference in the final $\braket{M_{\rm HI}}$ obtained when spectroscopic redshift uncertainties are accounted for in the stacking procedure ($ Δz\sim 0.00035$, i.e. $Δv \sim 100\,{\rm km\, s}^{-1}$). We also present a novel technique to increase the effective size of the galaxy sample by exploiting the geometric symmetries of galaxy cubelets, potentially enhancing the SNR by a factor $\sim\sqrt{2}$ when analyzing the final stacked spectrum (a factor 4 in a cubelet). This procedure is found to be robustly unbiased, while efficiently increasing the SNR, as expected. We argue that an appropriate framework employing detailed and realistic simulations is required to exploit upcoming datasets from SKA pathfinders in an accurate and reliable manner.
