A1795星系团中射电晕起源的强子模型下磁场的限制
Constraints on the magnetic field in the hadronic scenario for the origin of the radio halo in the A1795 galaxy cluster
AI总结：
研究A1795星系团射电晕强子起源假设下非热质子性质与磁场强度，通过假设磁场分布推导所需非热质子性质，计算伽马射线发射并与上限比较，得出强子模型需更大磁场值及相应非热质子分布特点。
AI中文摘要：
冷核星系团A1795中的射电晕最近被认为起源于强子，因其在Mpc量级尺度上延伸，而在松弛星系团中无湍流注入。本文旨在根据该星系团现有的伽马射线上限，在射电晕强子起源假设下限制非热质子性质和星系团磁场强度。假设磁场径向分布和中心强度的几个值，推导重现射电晕通量密度和表面亮度分布所需的非热质子相应性质，计算相应伽马射线发射并与费米大视场望远镜上限比较。结果表明，对于磁场能量径向分布遵循热分布的情况，磁场中心强度\(B_0<5\,\mu\)G时伽马射线发射高于费米大视场望远镜上限，因此强子模型需要更大磁场值。此时非热质子径向分布需随半径略有下降，虽比热分布慢。磁场值较小时则需要不同的产生或加速非热电子的机制。
英文摘要：
The radio halo in the cool-core galaxy cluster, A1795, has recently been proposed to be of hadronic origin, because it extends on megaparsec scales, where no turbulence is expected to be injected into a relaxed cluster. In this paper we aim to constrain the properties of nonthermal protons and the cluster magnetic field strength under the hypothesis of a hadronic origin for the radio halo in the light of the available gamma-ray upper limits for this cluster. We assumed a radial profile and several central magnetic field intensity values, then derived the corresponding properties of the nonthermal protons necessary to reproduce the flux density and surface brightness profile of the radio halo. For the obtained results, we calculated the corresponding gamma-ray emission and compared it with the Fermi-LAT upper limit. We find that, for a magnetic field energy radial profile following that of the thermal gas, central magnetic field intensities $B_0<5\,μ$G imply a gamma-ray emission at or above the Fermi-LAT upper limit. Therefore, larger values of the magnetic field are necessary in the hadronic scenario. For these values the radial profile of nonthermal protons must slightly decrease with radius, though more slowly than that of the thermal gas. For smaller values of the magnetic field, different mechanisms for producing or accelerating the nonthermal electrons are necessary.
