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arXiv 0704.3267astro-ph
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时滞透镜星系的径向密度分布

Radial density profiles of time-delay lensing galaxies

J. I. Read, P. Saha, A. V. Maccio

备注：
Replaced with final version accepted for publication in ApJ; very minor changes to text; high resolution figures may be obtained at justinread.net
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摘要：

本文给出了10个类星体强透镜星系的非参数径向质量分布。其中五个星系的轮廓接近$ρ(r)\propto r^{-2}$，而其余的更接近r^{-1}，与NFW轮廓一致。前者都是相对孤立的早期类型，并以恒星光为主。后者--尽管建模代码不知道这一点--要么在星系团中，要么具有非常高的质光比，这表明暗物质占主导地位的透镜（一个实际上是一对合并的星系）。相同的模型给出了$H_0^{-1} = 15.2_{-1.7}^{+2.5}\Gyr$（$H_0 = 64_{-9}^{+8} \legacy$），与先前的测定一致。当测试从宇宙流体动力学模拟的模拟透镜，我们的建模管道恢复H_0和$ρ(r)$估计的不确定性。我们的结果与最近的一些主张相反，这些主张认为透镜时间延迟意味着低的H_0或比r^{-2}陡得多的星系轮廓。我们诊断这些索赔是由于一个无效的建模近似：从幂律配置文件的小偏差有一个小的影响透镜的时间延迟。事实上，正如我们使用微扰理论和数值计算从星系形成模拟，一阶扰动的等温透镜可以产生零阶的时间延迟的变化。

英文摘要：

We present non-parametric radial mass profiles for ten QSO strong lensing galaxies. Five of the galaxies have profiles close to $ρ(r)\propto r^{-2}$, while the rest are closer to r^{-1}, consistent with an NFW profile. The former are all relatively isolated early-types and dominated by their stellar light. The latter --though the modeling code did not know this-- are either in clusters, or have very high mass-to-light, suggesting dark-matter dominant lenses (one is a actually pair of merging galaxies). The same models give $H_0^{-1} = 15.2_{-1.7}^{+2.5}\Gyr$ ($H_0 = 64_{-9}^{+8} \legacy$), consistent with a previous determination. When tested on simulated lenses taken from a cosmological hydrodynamical simulation, our modeling pipeline recovers both H_0 and $ρ(r)$ within estimated uncertainties. Our result is contrary to some recent claims that lensing time delays imply either a low H_0 or galaxy profiles much steeper than r^{-2}. We diagnose these claims as resulting from an invalid modeling approximation: that small deviations from a power-law profile have a small effect on lensing time-delays. In fact, as we show using using both perturbation theory and numerical computation from a galaxy-formation simulation, a first-order perturbation of an isothermal lens can produce a zeroth-order change in the time delays.

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