Light versus dark in strong-lens galaxies: dark matter haloes that are rounder than their stars
Light versus dark in strong-lens galaxies: dark matter haloes that are rounder than their stars
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DOI：
10.1093/mnras/stv2582
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发表时间：
2015-11
影响因子：
4.8
通讯作者：
C. Bruderer;J. Read;J. Coles;D. Leier;E. Falco;I. Ferreras;P. Saha
中科院分区：
文献类型：
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作者：
C. Bruderer;J. Read;J. Coles;D. Leier;E. Falco;I. Ferreras;P. Saha
我们测量了 11 个强透镜星系中恒星和暗物质质量分布的投影密度剖面、形状和排列。我们发现，在夏布里尔恒星初始质量函数的假设下，预测的暗物质密度分布显示出星系之间的显着差异。那些最外层图像超过 $\sim 10$ kpc 的图像非常适合投影的 NFW 轮廓；那些图像在 10 kpc 以内的恒星似乎比 NFW 更集中，正如预期的那样，如果它们的暗晕由于重子冷却而收缩的话。我们发现，在几个半光半径内，这些透镜的暗物质晕比它们的恒星质量分布更圆。虽然光环的椭圆度永远不会超过 $e_{dm} = 0.2$，但它们的恒星可以延伸到 $e_* > 0.2$。暗物质椭圆率高、外部剪切力弱的星系表现出强烈的光暗排列；那些具有强剪切力（$\gamma \gtrsim 0.1$）的可能会高度错位。这是令人放心的，因为孤立的未对准星系预计是不稳定的。我们的结果为星系形成模型提供了新的约束。对于给定的宇宙学，这些必须解释非常圆形的暗物质晕和未对准的强透镜系统的起源。
We measure the projected density profile, shape and alignment of the stellar and dark matter mass distribution in 11 strong-lens galaxies. We find that the projected dark matter density profile - under the assumption of a Chabrier stellar initial mass function - shows significant variation from galaxy to galaxy. Those with an outermost image beyond $\sim 10$ kpc are very well fit by a projected NFW profile; those with images within 10 kpc appear to be more concentrated than NFW, as expected if their dark haloes contract due to baryonic cooling. We find that over several half-light radii, the dark matter haloes of these lenses are rounder than their stellar mass distributions. While the haloes are never more elliptical than $e_{dm} = 0.2$, their stars can extend to $e_* > 0.2$. Galaxies with high dark matter ellipticity and weak external shear show strong alignment between light and dark; those with strong shear ($\gamma \gtrsim 0.1$) can be highly misaligned. This is reassuring since isolated misaligned galaxies are expected to be unstable. Our results provide a new constraint on galaxy formation models. For a given cosmology, these must explain the origin of both very round dark matter haloes and misaligned strong-lens systems.