具有自组织映射的表型红移：一种表征弱透镜源星系红移分布的新方法
Phenotypic redshifts with self-organizing maps: A novel method to characterize redshift distributions of source galaxies for weak lensing
摘要：
像暗能量巡天（DES）这样的宽视场成像巡天，依赖于对几个滤光片中光谱能量分布的粗略测量来估计源星系的红移分布。在这种情况下，样本方差、散粒噪声和选择效应限制了红移校准的准确性，从而限制了宇宙学约束的准确性。我们提出了一种新的方法，结合宽场，少过滤器的测量与目录从深领域与额外的过滤器和足够低的光度噪声，以打破光度红移简并。多波段深场被用作宽场观测和精确红移之间的中介，大大降低了样本方差、散粒噪声和选择效应。我们实现的方法使用自组织地图组星系的表型的基础上，他们观察到的通量，并使用模拟DES目录从N体模拟进行测试。它产生了一个典型的不确定性的平均红移在每个五个层析箱的DES第3年弱透镜层析分析$σ_{Δz} = 0.007$，这是一个60%的改善相比，第1年的分析的理想化模拟。虽然该方法的实施是专为DES，其形式主义可以适用于其他大型光度测量与类似的观测策略。
英文摘要：
Wide-field imaging surveys such as the Dark Energy Survey (DES) rely on coarse measurements of spectral energy distributions in a few filters to estimate the redshift distribution of source galaxies. In this regime, sample variance, shot noise, and selection effects limit the attainable accuracy of redshift calibration and thus of cosmological constraints. We present a new method to combine wide-field, few-filter measurements with catalogs from deep fields with additional filters and sufficiently low photometric noise to break degeneracies in photometric redshifts. The multi-band deep field is used as an intermediary between wide-field observations and accurate redshifts, greatly reducing sample variance, shot noise, and selection effects. Our implementation of the method uses self-organizing maps to group galaxies into phenotypes based on their observed fluxes, and is tested using a mock DES catalog created from N-body simulations. It yields a typical uncertainty on the mean redshift in each of five tomographic bins for an idealized simulation of the DES Year 3 weak-lensing tomographic analysis of $σ_{Δz} = 0.007$, which is a 60% improvement compared to the Year 1 analysis. Although the implementation of the method is tailored to DES, its formalism can be applied to other large photometric surveys with a similar observing strategy.
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