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arXiv 2309.06151astro-ph.HE
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利用伽马射线观测对矮球状星系中重暗物质湮灭的约束

Constraints on the annihilation of heavy dark matter in dwarf spheroidal galaxies with gamma-ray observations

Xiao-Song Hu, Ben-Yang Zhu, Tian-Ci Liu, Yun-Feng Liang

AI总结:

本研究利用Fermi-LAT对矮球状星系的观测,通过分析重暗物质湮灭产生的次级伽马射线信号,在10 GeV到100 PeV的宽质量范围内给出了暗物质湮灭截面的统一上限,拓展了现有约束的质量范围。

摘要:

暗物质湮灭产生的电子和正电子可通过同步辐射和逆康普顿(IC)过程产生次级辐射,这类次级辐射为探测质量超出探测器能量波段的暗物质(DM)粒子提供了一种可能途径。质量处于TeV-PeV范围的重暗物质(HDM)粒子的次级辐射位于Fermi-LAT的能量波段内。本文中,我们利用对矮球状(dSph)星系的Fermi-LAT观测来搜寻HDM粒子的湮灭信号。我们考虑了暗物质湮灭产生的正负电子($e^+/e^-$)在矮球状星系内的传播,通过求解传播方程推导得到平衡态的电子能谱,随后计算了该正负电子群通过IC和同步辐射过程产生的伽马射线信号。考虑到电子的空间扩散,我们根据预期的伽马射线空间强度分布,在Fermi-LAT数据分析中将矮球状星系建模为延展源。我们未探测到任何显著的HDM信号。在假设矮球状星系的磁场强度为$B=1\rm\thinspace μG$、扩散系数为$D_0 = 3\times10^{28}\rm\thinspace cm^{2}s^{-1}$的条件下,我们给出了HDM粒子湮灭截面的限制。我们的结果弱于此前VERITAS和IceCube对矮球状星系观测给出的限制,但将现有限制拓展到了更高的暗物质质量。作为补充,我们还搜寻了暗物质湮灭产生的瞬发伽马射线,并给出了10-$10^5$ GeV质量范围内的截面限制。综上,本文在统一的Fermi-LAT数据分析框架下,得到了10 GeV到100 PeV这一极宽质量范围内暗物质湮灭截面的上限。

英文摘要:

Electrons and positrons produced in dark matter annihilation can generate secondary emission through synchrotron and IC processes, and such secondary emission provides a possible means to detect DM particles with masses beyond the detector's energy band. The secondary emission of heavy dark matter (HDM) particles in the TeV-PeV mass range lies within the Fermi-LAT energy band. In this paper, we utilize the Fermi-LAT observations of dwarf spheroidal (dSph) galaxies to search for annihilation signals of HDM particles. We consider the propagation of $e^+/e^-$ produced by DM annihilation within the dSphs, derive the electron spectrum of the equilibrium state by solving the propagation equation, and then compute the gamma-ray signals produced by the $e^+/e^-$ population through the IC and synchrotron processes. Considering the spatial diffusion of electrons, the dSphs are modeled as extended sources in the analysis of Fermi-LAT data according to the expected spatial intensity distribution of the gamma rays. We do not detect any significant HDM signal. By assuming a magnetic field strength of $B=1\,{\rm μG}$ and a diffusion coefficient of $D_0 = 3\times10^{28}\,{\rm cm^{2}s^{-1}}$ of the dSphs, we place limits on the annihilation cross section for HDM particles. Our results are weaker than the previous limits given by the VERITAS and IceCube observations of dSphs, but extend the existing limits to higher DM masses. As a complement, we also search for the prompt $γ$-rays produced by DM annihilation and give limits on the cross section in the 10-$10^5$ GeV mass range. Consequently, in this paper we obtain the upper limits on the DM annihilation cross section for a very wide mass range from 10 GeV to 100 PeV in a unified framework of the Fermi-LAT data analysis.

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