论文标题
原始非高斯性和前景之间的堕落性在21厘米强度映射实验中
The degeneracy between primordial non-Gaussianity and foregrounds in 21cm intensity mapping experiments
论文作者
论文摘要
原始非高斯（PNG）的潜在证据预计将是宇宙学调查映射的最大尺度。即将进行的21厘米强度映射实验将旨在通过测量星系中的中性氢（HI）来探测这些尺度。但是，前景信号占据了微弱的21厘米发射，这意味着需要前景清洁才能恢复宇宙学信号。这确实是在最大的尺度上，尤其是在视线范围的情况下潮湿的HI功率谱。尽管达成共识，这种污染对于探测PNG可能是有问题的，但尚未对其进行充分探索和量化。在这项工作中，我们对$ f_ \ text {nl} $进行了第一个预测，该预测包含了使用真实数据中使用的技术删除的模拟前景图。使用MCMC分析，我们证明了前景清洁数据可恢复极有偏见的值（$ f_ \ text {nl} = -102.1 _ { - 7.96}^{+8.39} $ [68％cl]）上的$ f_ \ text {nl} = 0 $ purtucial输入。引入具有前景污染的固定参数的模型使我们能够恢复无偏的结果（$ f_ \ text {nl} = -2.94 _ { - 11.9}^{+11.4} $）。但是，尚不清楚我们将对前景污染有足够的了解以允许这种僵化的模型。将主要参数$ k_ \ parallel^\ text {fg} $在我们的前景模型中作为滋扰参数，并且在其上进行边缘化，但仍然恢复了无偏见的结果，但以更大的错误为代价（$ f_ \ text {nl} = 0.75^= 0.75^{+40.2}} $ teles the the the Inlanct yeflancs yeflancs ye tem y the n off yection y the te pe labinct ye teles te laxphancs ye temanct y te pe lax the te pe lax te pe pelanct y。我们的结果表明，为了使用HI强度映射研究PNG，必须在理解和控制前景拆卸效果方面取得重大进展。
Potential evidence for primordial non-Gaussianity (PNG) is expected to lie in the largest scales mapped by cosmological surveys. Forthcoming 21cm intensity mapping experiments will aim to probe these scales by surveying neutral hydrogen (HI) within galaxies. However, foreground signals dominate the faint 21cm emission, meaning foreground cleaning is required to recover the cosmological signal. The effect this has is to damp the HI power spectrum on the largest scales, especially along the line-of-sight. Whilst there is agreement that this contamination is potentially problematic for probing PNG, it is yet to be fully explored and quantified. In this work we carry out the first forecasts on $f_\text{NL}$ that incorporate simulated foreground maps that are removed using techniques employed in real data. Using an MCMC analysis, we demonstrate that foreground cleaned data recovers hugely biased values ($f_\text{NL} = -102.1_{-7.96}^{+8.39}$ [68% CL]) on our $f_\text{NL}=0$ fiducial input. Introducing a model with fixed parameters for the foreground contamination allows us to recover unbiased results ($f_\text{NL} = -2.94_{-11.9}^{+11.4}$). However, it is not clear that we will have sufficient understanding of foreground contamination to allow for such rigid models. Treating the main parameter $k_\parallel^\text{FG}$ in our foreground model as a nuisance parameter and marginalizing over it, still recovers unbiased results but at the expense of much larger errors ($f_\text{NL} = 0.75^{+40.2}_{-44.5}$), that can only be reduced by imposing the Planck 2018 prior. Our results show that significant progress on understanding and controlling foreground removal effects is necessary in order to study PNG with HI intensity mapping.
