系统不确定性及其对矮星系暗物质伽马射线搜索的影响
Systematic Uncertainties and Their Impact on Gamma-Ray Searches for Dark Matter in Dwarf Galaxies
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中文总结 AI 辅助
该研究回顾了矮星系J-因子确定中的多种系统不确定性，并通过模拟费米-拉特观测量化其对暗物质湮灭约束的影响，发现未建模不确定性会显著削弱堆叠分析的上限并导致覆盖不足。
中文摘要 AI 辅助
对银河系矮卫星星系的伽马射线观测为暗物质湮灭提供了最强的一些约束，并且正接近检验银河系中心伽马射线过剩的暗物质解释所需的灵敏度。然而，结果关键地依赖于这些系统中推断出的暗物质分布，通常由其$J$-因子和空间轮廓来描述。我们回顾了矮星系$J$-因子确定中系统不确定性的几个来源，包括恒星成员资格、未分辨的双星、偏离平衡和球对称性，以及关于恒星和暗物质密度轮廓的假设。文献中报道的大多数$J$-因子确定忽略了其中几种不确定性，由此得到的测量结果通常比其引用的不确定性所暗示的更为分散。这表明对于许多这样的系统，可能需要约$\Delta\log_{10}J\sim0.5$或更大的不确定性。利用对27个矮星系堆叠样本的模拟费米-拉特观测集合，我们量化了这些未建模的不确定性如何影响对暗物质湮灭截面的约束。我们发现，将$\Delta\log_{10}J\sim 0.5$或1.0的不确定性以平方和方式加入，会使堆叠分析的中位上限分别减弱1.4倍或3.2倍。此外，低估这些不确定性可能导致此类分析比名义置信水平更频繁地排除真实湮灭截面。这种覆盖不足在堆叠分析中尤为明显，即使采用的和真实的$J$-因子不确定性一致时仍然存在。将空间扩展的晕错误建模为点源（有时这样做）会进一步加强所得限制，并增加真实信号被错误排除的概率。
英文摘要
Gamma-ray observations of Milky Way dwarf galaxies provide some of the strongest constraints on dark matter annihilation and are approaching the sensitivity required to test dark matter interpretations of the Galactic Center Gamma-Ray Excess. The results, however, depend critically on the inferred dark matter distributions in these systems, conventionally described by their $J$-factors and spatial profiles. We review several sources of systematic uncertainty in dwarf galaxy $J$-factor determinations, including stellar membership, unresolved binaries, departures from equilibrium and spherical symmetry, and assumptions regarding the stellar and dark matter density profiles. Most $J$-factor determinations reported in the literature neglect several of these uncertainties, and the resulting measurements are often more dispersed than their quoted uncertainties would suggest. This indicates uncertainties of order $Δ\log_{10}J\sim0.5$ or larger may be warranted for many of these systems. Using an ensemble of simulated Fermi-LAT observations of a stacked sample of 27 dwarf galaxies, we quantify how these unmodeled uncertainties affect the resulting constraints on the dark matter annihilation cross section. We find that adding an uncertainty of $Δ\log_{10}J\sim 0.5$ or 1.0 in quadrature weakens the median upper limits of a stacked analysis by factors of 1.4 or 3.2, respectively. Furthermore, underestimating these uncertainties can cause such analyses to exclude the true annihilation cross section more frequently than the nominal confidence level would imply. Such undercoverage is especially pronounced in stacked analyses and persists even when the adopted and true $J$-factor uncertainties agree. Mismodeling spatially extended halos as point sources, as is sometimes done, further strengthens the resulting limits and increases the probability that true signals will be incorrectly excluded.
发表机构
- University of Wisconsin, Madison（威斯康星大学麦迪逊分校）
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