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arXiv 2607.08552astro-ph.HEhep-ex
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20 GeV银河系晕圈过剩:像素级确认及与亚 TeV 弱相互作用大质量粒子湮灭的一致性

The 20 GeV Galactic Halo Excess: Pixel-Level Confirmation and Consistency with Sub-TeV WIMP Annihilation

University College London(伦敦大学学院)

Trinity Rosebud Stenhouse, Chamkaur Ghag, Frank F. Deppisch

AI总结:

研究基于Fermi-LAT数据,对20GeV银河系晕圈过剩进行像素级确认及分析,重现其光谱,与WIMP湮灭一致,拟合得出最佳质量和〈σv〉,存在张力,考虑多种暗物质模型后,低速增强湮灭是唯一可行结构,有望解决矮星系张力。

摘要:

最近一项对15年费米大面积望远镜(Fermi-LAT)数据的分析报告称,银河系弥漫发射存在一个球对称、类似晕圈的成分,在20GeV附近达到峰值。我们独立重现了这种细胞聚集分析,然后将其扩展到原生0.125°地图上的像素级似然分析,增加了能量依赖的点扩散函数前向折叠并屏蔽亮源。两种方法都重现了20GeV晕圈光谱,在NFW发射率标度ρ^p(p∈1,2,2.5)上,像素级归一化比细胞级拟合高约20%。这个20GeV晕圈是一个高纬度特征,与银河系内部过剩不同,且与亚 TeV 暗物质(WIMP)湮灭一致。它集中在中心,强烈不支持河外发射。拟合即时s波湮灭光谱,最佳拟合质量为m_χ≃0.55 TeV(W^+W^-)和0.72 TeV(b\bar{b}),〈σv〉≃1×10^-24 cm^3 s^-1,与矮球状星系极限存在约4 - 5倍的张力。然而,考虑前景建模和J因子系统不确定性会将张力窗口扩大到R≃1.6 - 9.3,使s波解释仍然可行。为了消除张力,我们考虑了替代粒子暗物质模型。p波湮灭错过遗迹丰度约束约7个数量级。衰变解释避开了矮星系极限,但不被各向同性伽马射线背景支持。唯一与矮星系极限、当前晕圈速率和遗迹密度一致的可行速度结构是低速增强湮灭(共振索末菲或 Breit-Wigner)。这提供了从热遗迹所需的约45倍增强。完全解决矮星系张力需要在晕圈速度处微调共振并在较冷系统中下降。

英文摘要:

A recent analysis of 15 years of Fermi-LAT data reported a spherically symmetric, halo-like component of the Galactic diffuse emission that peaks near 20GeV. We independently reproduce this cell-aggregated analysis, then extend it to a pixel-level likelihood on the native $0.125^\circ$ maps, adding energy-dependent point-spread-function forward folding and masking bright sources. Both methods replicate the 20GeV halo spectrum, with the pixel-level normalisation ${\sim}20\%$ above the cellwise fit across NFW emissivity scalings $ρ^p$, $p \in 1,2,2.5$. This 20GeV halo is a high-latitude feature, distinct from the inner-Galaxy excess, and consistent with sub-TeV dark matter (WIMP) annihilation. It is centrally concentrated, strongly disfavouring extragalactic emission. Fitting prompt $s$-wave annihilation spectra, best-fit masses are $m_χ\simeq 0.55$TeV ($W^+W^-$) and $0.72$TeV ($b\bar{b}$) with $\langleσv\rangle \simeq 1\times10^{-24}~\mathrm{cm^3\,s^{-1}}$, in $\sim\!4$-$5\times$ tension with dwarf spheroidal galaxy limits. However, accounting for foreground modelling and $J$-factor systematic uncertainties widens the tension window to $R\simeq1.6$-$9.3$, leaving the $s$-wave interpretation viable. To close the tension, we consider alternative particle dark matter models. $p$-wave annihilation misses relic abundance constraints by $\sim\!7$ orders of magnitude. A decay interpretation evades dwarf limits but is disfavoured by the isotropic gamma-ray background. The only viable velocity structure consistent with dwarf limits, present-day halo rates, and relic density is low-velocity-enhanced annihilation (resonant Sommerfeld or Breit-Wigner). This supplies the required $\approx\!45\times$ boost from a thermal relic. Fully resolving the dwarf tension requires a fine-tuned resonance peaking at the halo velocity and falling for colder systems.

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