Gravitational lensing time delays offer an avenue to measure the Hubble parameter $H_0$, with some analyses suggesting a tension with early-type probes of $H_0$. The lensing measurements must mitigate systematic uncertainties due to the mass modeling of lens galaxies. In particular, a core component in the lens density profile would form an approximate local mass sheet degeneracy and could bias $H_0$ in the right direction to solve the lensing tension. We consider ultralight dark matter as a possible mechanism to generate such galactic cores. We show that cores of roughly the required properties could arise naturally if an ultralight axion of mass $m\sim {10}^{-25}\mathrm{eV}$ makes up a fraction of order 10% of the total cosmological dark matter density. A relic abundance of this order of magnitude could come from vacuum misalignment. Stellar kinematics measurements of well-resolved massive galaxies (including the Milky Way) may offer a way to test the scenario. Kinematics analyses aiming to test the core hypothesis in massive elliptical lens galaxies should not, in general, adopt the perfect mass sheet limit, as ignoring the finite extent of an actual physical core could lead to significant systematic errors.

中文翻译：

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超轻轴子星系核的引力透镜H0张力

引力透镜时间延迟提供了一种测量哈勃参数的途径 $H_0$，一些分析表明与早期类型的探测存在紧张关系 $H_0$. 由于透镜星系的质量建模，透镜测量必须减轻系统的不确定性。特别是，透镜密度分布中的核心成分会形成近似的局部质量片简并，并可能产生偏差$H_0$以正确的方向解决镜片张力。我们认为超轻暗物质是产生这种星系核的一种可能机制。我们表明，如果质量超轻的轴子可以自然产生具有大致所需特性的核心$米～{10}^{-25}\mathrm{电动汽车}$占宇宙暗物质总密度的 10% 左右。这个数量级的大量遗迹可能来自真空未对准。对分辨率良好的大质量星系（包括银河系）进行的恒星运动学测量可能会提供一种测试场景的方法。旨在检验大质量椭圆透镜星系核心假设的运动学分析通常不应采用完美质量片限制，因为忽略实际物理核心的有限范围可能会导致显着的系统误差。