Reconstructing the lensing mass in the Universe from photometric catalogue data
Reconstructing the lensing mass in the Universe from photometric catalogue data
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DOI：
10.1093/mnras/stt504
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发表时间：
2013-06-01
影响因子：
4.8
通讯作者：
Blandford, Roger D.
中科院分区：
文献类型：
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作者：
Collett, Thomas E.;Marshall, Philip J.;Blandford, Roger D.
对单个物体的高精度宇宙学距离测量，如时延引力透镜或Ia型超新星，受到视线上星系和群体的弱透镜扰动的影响。在时延引力透镜中，“外部会聚”kappa(Ext)可以控制推断距离的不确定性，从而决定宇宙学参数。在这篇文章中，我们尝试用一个简单的晕模型来重建视线结构的kappa(Ext)。我们使用来自千禧年模拟的模拟星表，校准和比较我们重建的P(kappa(Ext))和光线跟踪kappa(Ext)的‘真相’值；考虑到红移和恒星质量的现实不确定性。我们发现，Kappa(Ext)的重建提供了与星系数计数类似50%的精度改进。我们发现最低的kappa(Ext)视线有最好的约束P(kappa(Ext))。考虑到未来将有数千个透镜的样本，我们发现，选择具有最高精度kappa(EXT)估计的三分之一的系统可以提供无偏时延距离测量的子样本，由于视线外部会聚效应，(平均)只有1%的不确定度。仅光度学数据就足以预先选择最佳约束的视线，并且可以在投资于光曲线监测之前完成。相反，我们表明，利用这里提出的重建模型，选择具有高外部剪切的视线可以在时间延迟距离中产生高达1%的偏差。我们发现，系统误差的一个主要潜在来源是恒星质量-晕质量关系的高质量端的不确定性；如果完全忽略这一点，可能会在时间延迟距离上引入类似2%的偏差。我们建议改进这一一般分析框架的领域(包括对高质量结构的更复杂的处理)，这应该允许做出更准确的宇宙学推断。
High precision cosmological distance measurements towards individual objects such as time delay gravitational lenses or Type Ia supernovae are affected by weak lensing perturbations by galaxies and groups along the line of sight. In time delay gravitational lenses, 'external convergence', kappa(ext), can dominate the uncertainty in the inferred distances and hence cosmological parameters. In this paper we attempt to reconstruct kappa(ext), due to line of sight structure, using a simple halo model. We use mock catalogues from the Millennium Simulation, and calibrate and compare our reconstructed P(kappa(ext)) to ray-traced kappa(ext) 'truth' values; taking into account realistic uncertainties on redshift and stellar masses. We find that the reconstruction of kappa(ext) provides an improvement in precision of similar to 50 per cent over galaxy number counts. We find that the lowest kappa(ext) lines of sight have the best constrained P(kappa(ext)). In anticipation of future samples with thousands of lenses, we find that selecting the third of the systems with the highest precision kappa(ext) estimates gives a subsample of unbiased time delay distance measurements with (on average) just 1 per cent uncertainty due to line of sight external convergence effects. Photometric data alone are sufficient to pre-select the best-constrained lines of sight, and can be done before investment in light-curve monitoring. Conversely, we show that selecting lines of sight with high external shear could, with the reconstruction model presented here, induce biases of up to 1 per cent in time delay distance. We find that a major potential source of systematic error is uncertainty in the high-mass end of the stellar mass-halo mass relation; this could introduce similar to 2 per cent biases on the time delay distance if completely ignored. We suggest areas for the improvement of this general analysis framework (including more sophisticated treatment of high-mass structures) that should allow yet more accurate cosmological inferences to be made.