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arXiv 1601.02181astro-ph.HE
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矮星系Fermi-LAT观测中速度相关的暗物质湮灭截面的约束

Constraint on the velocity dependent dark matter annihilation cross section from Fermi-LAT observations of dwarf galaxies

Yi Zhao, Xiao-Jun Bi, Huan-Yu Jia, Peng-Fei Yin, Feng-Rong Zhu

摘要:

对矮椭球卫星的伽玛射线观测是探测暗物质湮灭特征的理想途径。最新的Fermi-LAT dSph搜索对小DM质量范围内的速度无关湮灭截面设置了严格的约束,这对解释AMS-02正电子过剩的DM湮灭方案给出了非常强的约束。然而,dSph的约束将改变速度依赖的湮灭的情况下,因为在dSph的速度分散在不同的银河系。在这项工作中,我们使用的似然映射方法来设置约束的速度依赖的湮灭截面从费米-LAT观测6 dSphs。我们考虑了三种典型形式的湮灭截面,即p波湮灭,索末菲增强和Breit-Wigner共振。对于p波湮灭和Sommerd-enhancement,dSph极限分别比速度无关湮灭的dSph极限弱得多,而对于Sommerd-enhancement,dSph极限比速度无关湮灭的dSph极限强得多。对于Breit-Wigner湮灭,dSph极限将根据模型参数而变化。我们表明,该方案来解释AMS-02的正电子过剩DM湮没在速度依赖的情况下仍然是可行的。

英文摘要:

The gamma-ray observation of dwarf spheroidal satellites (dSphs) is an ideal approach for probing the dark matter (DM) annihilation signature. The latest Fermi-LAT dSph searches have set stringent constraints on the velocity independent annihilation cross section in the small DM mass range, which gives very strong constraints on the scenario to explain the the AMS-02 positron excess by DM annihilation. However, the dSph constraints would change in the velocity dependent annihilation scenarios, because the velocity dispersion in the dSphs varies from that in the Milky Way. In this work, we use a likelihood map method to set constraints on the velocity dependent annihilation cross section from the Fermi-LAT observation of six dSphs. We consider three typical forms of the annihilation cross section, i.e. p-wave annihilation, Sommerfeld enhancement, and Breit-Wigner resonance. For the p-wave annihilation and Sommerfeld-enhancement, the dSph limits would become much weaker and stronger compared with those for the velocity independent annihilation, respectively. For the Breit-Wigner annihilation, the dSph limits would vary depending on the model parameters. We show that the scenario to explain the AMS-02 positron excess by DM annihilation is still viable in the velocity dependent cases.

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