Hints for decaying dark matter from $S_8$ measurements
Hints for decaying dark matter from $S_8$ measurements
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$S_8$ 测量中暗物质衰变的提示
DOI：
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发表时间：
2020
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影响因子：
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通讯作者：
J. Lavalle
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作者：
G. Abellán;R. Murgia;V. Poulin;J. Lavalle
最近的弱透镜观测显示，直接测量参数组合S_8\equiv\sigma_8（\Omega_m/0.3）^{0.5}$ --测量8 $h^{-1}$Mpc尺度上物质波动的幅度--与假设$\Lambda$CDM模型从宇宙微波背景（CMB）数据重建的值不一致。在这封信中，我们表明，如果暗物质（DM）以$\text{log}_{10}的寿命衰变，则有可能解决张力（\Gamma^{-1}/ \text{Gyr}）= 1.75_{-0.95}^{+1.4}$分为一个无质量和一个有质量的产物，并将其静止质量能量的一小部分转移到无质量分量。的速度踢收到的大规模的女儿导致抑制重力集群低于其自由流长度，从而减少了$\sigma_8 $值相比，从标准的$\Lambda$CDM模型推断，在类似的方式，大规模中微子和标准的温暖DM。与后一种情况类似，功率抑制和自由流尺度的时间依赖性允许2体衰变DM情况容纳CMB，重子声振荡，生长因子和未校准的超新星Ia数据。我们简要讨论DM模型的建设，银河系小尺度结构问题和最近的氙-1T过剩的影响。未来在$0\lesssim z\lesssim 1 $处测量高精度生长因子的实验可以进一步测试这种情况。
Recent weak lensing surveys have revealed that the direct measurement of the parameter combination $S_8\equiv\sigma_8(\Omega_m/0.3)^{0.5}$ -- measuring the amplitude of matter fluctuations on 8 $h^{-1}$Mpc scales -- is $\sim3\sigma$ discrepant with the value reconstructed from cosmic microwave background (CMB) data assuming the $\Lambda$CDM model. In this Letter, we show that it is possible to resolve the tension if dark matter (DM) decays with a lifetime of $\text{log}_{10}(\Gamma^{-1}/ \text{Gyr})= 1.75_{-0.95}^{+1.4}$ into one massless and one massive product, and transfers a fraction $\varepsilon\simeq 0.7^{+2.7}_{-0.6}\%$ of its rest mass energy to the massless component. The velocity-kick received by the massive daughter leads to a suppression of gravitational clustering below its free-streaming length, thereby reducing the $\sigma_8$ value as compared to that inferred from the standard $\Lambda$CDM model, in a similar fashion to massive neutrino and standard warm DM. Contrarily to the latter scenarios, the time-dependence of the power suppression and the free-streaming scale allows the 2-body decaying DM scenario to accommodate CMB, baryon acoustic oscillation, growth factor and uncalibrated supernova Ia data. We briefly discuss implications for DM model building, galactic small-scale structure problems and the recent Xenon-1T excess. Future experiments measuring the growth factor to high accuracy at $0\lesssim z\lesssim1$ can further test this scenario.