arXiv 1908.103692019-08astro-ph.CO

约束非热暗物质对物质功率谱的影响

Constraining Nonthermal Dark Matter's Impact on the Matter Power Spectrum

Carisa Miller, Adrienne Erickcek, Riccardo Murgia

备注：: To be submitted to PRD; 14 pages, 13 figures; Updated to match published version
发表信息：: Phys. Rev. D 100, 123520 (2019)
DOI：: 10.1103/PhysRevD.100.123520

摘要：

在暴胀之后和辐射支配开始之前，包含一个（有效）物质支配时期对结构增长有着有趣和可观察的影响。在这个早期的物质主导时代（EMDE），宇宙被大质量粒子或振荡标量场所主导，这些粒子衰变为标准模型粒子，从而重新加热了宇宙。这种衰变过程也可能是暗物质的主要来源。在母粒子和子粒子质量之间没有微调的情况下，暗物质粒子和标准模型粒子都将以相对论速度产生。通过确定暗物质的速度分布函数，我们研究了具有相对论速度的暗物质粒子的非热产生对物质功率谱的影响。我们发现，绝大多数的暗物质粒子在EMDE过程中产生的仍然是相对论性的再加热，所以他们的自由流擦除的扰动，在EMDE增长。暗物质粒子的自由流动也可以阻止银河系周围卫星星系的形成以及在莱曼- $α$森林中观察到的结构。对于一个给定的再加热温度，这些观测为暗物质粒子在其产生时的速度设定了上限。例如，对于10 MeV的再加热温度，暗物质必须以洛伦兹因子$γ\lesssim 550$产生。

英文摘要：

The inclusion of a period of (effective) matter domination following inflation and prior to the onset of radiation domination has interesting and observable consequences for structure growth. During this early matter-dominated era (EMDE), the Universe was dominated by massive particles, or an oscillating scalar field, that decayed into Standard Model particles, thus reheating the Universe. This decay process could also be the primary source of dark matter. In the absence of fine-tuning between the masses of the parent and daughter particles, both dark matter particles and Standard Model particles would be produced with relativistic velocities. We investigate the effects of the nonthermal production of dark matter particles with relativistic velocities on the matter power spectrum by determining the resulting velocity distribution function for the dark matter. We find that the vast majority of dark matter particles produced during the EMDE are still relativistic at reheating, so their free streaming erases the perturbations that grow during the EMDE. The free streaming of the dark matter particles can also prevent the formation of satellite galaxies around the Milky Way and the structures observed in the Lyman-$α$ forest. For a given reheat temperature, these observations put an upper limit on the velocity of the dark matter particles at their creation. For example, for a reheat temperature of 10 MeV, dark matter must be produced with a Lorentz factor $γ\lesssim 550$.

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