In this paper we analyze a simple scenario in which Dark Matter (DM) consists of free fermions with mass $m_f$. We assume that on galactic scales these fermions are capable of forming a degenerate Fermi gas, in which stability against gravitational collapse is ensured by the Pauli exclusion principle. The mass density of the resulting configuration is governed by a non-relativistic Lane-Emden equation, thus leading to a universal cored profile that depends only on one free parameter in addition to $m_f$. After reviewing the basic formalism, we test this scenario against experimental data describing the velocity dispersion of the eight classical dwarf spheroidal galaxies of the Milky Way. We find that, despite its extreme simplicity, the model exhibits a good fit to the data and realistic predictions for the size of DM halos providing that $m_f\simeq 200$ eV. Furthermore, we show that in this setup larger galaxies correspond to the non-degenerate limit of the gas. We propose a concrete realization of this model in which DM is produced non-thermally via inflaton decay. We show that imposing the correct relic abundance and the bound on the free-streaming length constrains the inflation model in terms of inflaton mass, its branching ratio into DM and the reheating temperature.
Dark matter self-interactions from the internal dynamics of dwarf spheroidals
矮椭球星系对标准的冷和无碰撞暗物质方案提出了众所周知的挑战：太大而不能倒的问题，即矮椭球星系半光半径内的观测质量与冷暗物质N体预测之间的不匹配;内部恒定密度核心的暗示。虽然这些争议可能会被重子物理学和环境效应所缓解，但重新审视冷和无碰撞的暗物质的标准知识仍然是一个有趣的可能性。自相互作用的暗物质可能是解决这种小规模危机的成功方案。自相互作用关联了暗物质和重子的分布，使得在低表面亮度的星系中有恒定密度的核心。在这里，我们报告的第一个数据驱动的研究太大而不能失败的银河系矮球体内的自相互作用的暗物质范例。从最近的纯冷暗物质模拟中，我们发现了恒星运动学的良好描述和与浓度-质量关系的兼容性。在这种浓度-质量关系中，一部分银河系矮星的横截面为0.5-3 cm $^2$ /g，而其他的则大于10 cm $^2$ /g。
Discovery prospects of dwarf spheroidal galaxies for indirect dark matter searches
我们研究了大型巡天望远镜（LSST）在银河系中发现新矮球状星系的前景。采用Milky-Way晕子结构模型和连接暗晕和卫星星系的唯象公式，我们得到了$V$波段的表面亮度分布，预测LSST将发现几十到几百个高于其灵敏度的矮球状星系。即将被发现的矮星将是间接寻找暗物质湮灭产率的有趣目标。我们预测了这些天体中暗物质湮灭产生的γ射线辐射的分布函数，并讨论了这些信号在费米大天区望远镜（LAT）和切伦科夫望远镜阵列（CTA）上的可探测性。通过结合预测的矮星系的信息，我们得到了预期的灵敏度$10^{-26}$ cm $^3$ s $^{-1}$（对于质量为10 GeV的暗物质粒子与费米LAT）和$5\times 10^{-24}$ cm $^3$ s $^{-1}$（对于质量为500 GeV的暗物质粒子与CTA）的湮灭截面$\langle σv \rangle$。我们发现，目前的不确定性的银河晕的质量测量是相对较小的泊松误差相比，绘制最有前途的矮星从底层的通量分布。
