We demonstrate that the perturbations of strongly lensed images by low-mass dark matter subhaloes are significantly impacted by the concentration of the perturbing subhalo. For subhalo concentrations expected in Lambda cold dark matter (ΛCDM), significant constraints on the concentration can be obtained at Hubble Space Telescope (HST) resolution for subhaloes with masses larger than about $10^{10}\, {\rm M}_\odot$. Constraints are also possible for lower mass subhaloes, if their concentrations are higher than the expected scatter in CDM. We also find that the concentration of lower mass perturbers down to $\sim 10^8\, {\rm M}_\odot$ can be well constrained with a resolution of ∼0.01 arcsec, which is achievable with long-baseline interferometry. Subhalo concentration also plays a critical role in the detectability of a perturbation, such that only high-concentration perturbers with mass $\lesssim 10^9\, {\rm M}_\odot$ are likely to be detected at HST resolution. If scatter in the ΛCDM mass–concentration relation is not accounted for during lens modelling, the inferred subhalo mass can be biased by up to a factor of 3 (6) for subhaloes of mass $10^9 \, {\rm M}_\odot \,(10^{10} \, {\rm M}_\odot$); this bias can be eliminated if one varies both mass and concentration during lens fitting. Alternatively, one may robustly infer the projected mass within the subhalo’s perturbation radius, defined by its distance to the critical curve of the lens being perturbed. With a sufficient number of detections, these strategies will make it possible to constrain the halo mass–concentration relation at low masses in addition to the mass function, offering a probe of dark matter physics as well as the small-scale primordial power spectrum.

中文翻译：

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推断扰动强透镜图像的暗物质亚晕的浓度

我们证明了低质量暗物质亚晕对强透镜图像的扰动受到扰动亚晕浓度的显着影响。对于 Lambda 冷暗物质 (ΛCDM) 中预期的亚晕浓度，对于质量大于约 $10^{10}\, {\rm M}_\点$。如果它们的浓度高于 CDM 中的预期散射，则对质量较低的亚晕也可能进行约束。我们还发现，低至 $\sim 10^8\, {\rm M}_\odot$ 的较低质量扰动剂的浓度可以通过 ∼0.01 弧秒的分辨率得到很好的约束，这可以通过长基线干涉测量来实现。亚晕浓度在扰动的可检测性中也起着关键作用，这样只有质量为 $\lesssim 10^9\, {\rm M}_\odot$ 的高浓度扰动物才有可能在 HST 分辨率下被检测到。如果在透镜建模期间不考虑 ΛCDM 质量-浓度关系中的散射，对于质量为 $10^9 \, {\rm M}_\ odot \,(10^{10} \, {\rm M}_\odot$); 如果在镜片装配过程中同时改变质量和浓度，则可以消除这种偏差。或者，可以稳健地推断子晕的扰动半径内的投影质量，由其到被扰动的透镜的临界曲线的距离定义。通过足够数量的检测，这些策略将使得除了质量函数之外，还可以约束低质量的晕质量 - 浓度关系，