标题： M31中无线电发射形状对暗物质湮灭的限制 显示英文标题

标题： Limits on Dark Matter Annihilation from the Shape of Radio Emission in M31

摘要： 具有良好动机的热产生暗物质情景通常会导致星系中通过暗物质湮灭产生的电子和正电子群体——通常与高能伽马射线相关联。 当它们通过星系磁场扩散时，这些 $e^\pm$ 会产生同步辐射射电发射。 该信号的强度和形态取决于星际介质的特性，这些介质是 $e^\pm$ 所传播的。 利用对仙女座星系（M31）的观测来构建气体、磁场和恒星光的模型，我们通过3.6厘米射电发射的形态对暗物质湮灭到 $b\bar{b}$ 设置限制。 由于M31中心的发射信号对扩散系数和暗物质分布非常敏感，我们将限制基于中心周围 $0.9-6.9$ 千秒差距区域内的微分通量。 我们排除了质量范围$\gtrsim 3 \times 10^{-25}$ GeV 内的湮灭截面$^3$ cm$10-500$/s，在$7\times 10^{-26}$ GeV 处的最大灵敏度为$^3$ cm$20-40$/s。 尽管这些限制比之前对 M31 的研究结果弱，但它们对扩散系数的变化是稳健的。 显示英文摘要

摘要： Well-motivated scenarios of thermally-produced dark matter often result in a population of electrons and positrons within galaxies produced through dark matter annihilation -- often in association with high-energy gamma rays. As they diffuse through galactic magnetic fields, these $e^\pm$ produce synchrotron radio emission. The intensity and morphology of this signal depends on the properties of the interstellar medium through which the $e^\pm$ propagate. Using observations of the Andromeda Galaxy (M31) to construct a model of the gas, magnetic fields, and starlight, we set constraints on dark matter annihilation to $b\bar{b}$ using the morphology of 3.6 cm radio emission. As the emission signal at the center of M31 is very sensitive to the diffusion coefficient and dark matter profile, we base our limits on the differential flux in the region between $0.9-6.9$ kpc from the center. We exclude annihilation cross sections $\gtrsim 3 \times 10^{-25}$ cm$^3$/s in the mass range $10-500$ GeV, with a maximum sensitivity of $7\times 10^{-26}$ cm$^3$/s at $20-40$ GeV. Though these limits are weaker than those found in previous studies of M31, they are robust to variations of the diffusion coefficient.