GRAINE 2023乳胶望远镜在亚GeV波段搜寻银河系中心过量辐射的初步结果

中文摘要 AI 辅助

银河系中心过量（GCE）是一种来自银河系中心的未解释的伽马射线发射过量现象。GRAINE实验旨在利用乳胶伽马射线望远镜揭示GCE的起源，该望远镜在100 MeV时具有1度的高角分辨率，在1 GeV时具有0.1度的高角分辨率。在本研究中，我们利用GRAINE 2023飞行数据在银河系中心附近的一个小区域内搜寻GCE。特别地，我们并未聚焦于GCE在2 GeV处的谱峰，而是关注了低于300 MeV的能量范围，在该范围内暗物质湮灭和毫秒脉冲星情景之间的谱差异更为显著。我们在75–300 MeV能量范围内，在银河系中心1度范围内搜寻了GCE。尽管未观察到显著过量，但基于对银河系中心周围狭窄区域的直接观测，我们在以银河系中心为中心的1度半径感兴趣区域（ROI）内，以2西格玛置信水平获得了GCE通量的上限为1.70×10^-7 GeV cm^-2 s^-1。这一观测需要高角分辨率，代表了GRAINE的一项独特成果。所获得的上限与从现有Fermi-LAT观测中利用宽ROI并假设NFW轮廓估算的银河系中心附近的GCE通量一致。尽管当前上限约束了一些模型，但现有统计量仍不足以区分暗物质湮灭和毫秒脉冲星情景，两者都与当前结果一致。我们还基于本次观测估算了未来GRAINE实验的预期灵敏度，并通过将预期灵敏度与预测的GCE谱进行比较，展示了其探测GCE起源的潜力。

英文摘要

(Please check the paper for full abstract.) The Galactic Center Excess (GCE) is an unexplained excess of gamma-ray emission from the Galactic Center. The GRAINE experiment aims to reveal the origin of the GCE using an emulsion gamma-ray telescope with high angular resolutions of 1 deg at 100 MeV and 0.1 deg at 1 GeV. In this study, we search for the GCE in a small region near the Galactic Center using the GRAINE 2023 flight data. In particular, rather than focusing on the spectral peak of the GCE at 2 GeV, we focused on the energy range below 300 MeV, where the spectral differences between the dark matter annihilation and millisecond pulsar scenarios are more pronounced. We searched for the GCE within 1 deg of the Galactic Center in the 75--300 MeV energy range. Although no significant excess was observed, we obtained an upper limit on the GCE flux of 1.70*10^-7 GeV cm^-2 s^-1 at the 2 sigma confidence level for the 1deg-radius ROI centered on the Galactic Center, based on a direct observation of the narrow region around the Galactic Center. This observation requires high angular resolution and represents a unique result from GRAINE. The obtained upper limit is consistent with the GCE flux near the Galactic Center, which was estimated from existing Fermi-LAT observations using a wide ROI and assuming an NFW profile. Although the current upper limit constrains some models, the available statistics are still insufficient to distinguish between the dark matter annihilation and millisecond pulsar scenarios, and both remain consistent with the current results. We also estimated the projected sensitivity of future GRAINE experiments based on the present observation and demonstrated their potential to probe the origin of the GCE by comparing the projected sensitivity with the predicted GCE spectra.

发表机构

• Kobayashi-Maskawa Institute for the Origin of Particles and the Universe (KMI), Nagoya University（名古屋大学小林-益川粒子宇宙起源研究所）
• Graduate School of Science, Nagoya University（名古屋大学理学研究科）
• Graduate School of Human Development and Environment, Kobe University（神户大学人类发展与环境学研究科）
• Graduate School of Science and Engineering, Okayama University of Science（冈山理科大学理工学研究科）
• Faculty of Education, Aichi University of Education（爱知教育大学教育学部）

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