CLASH-VLT: A highly precise strong lensing model of the galaxy cluster RXC J2248.7 - 4431 (Abell S1063) and prospects for cosmography-猫眼课题宝

DOI：

10.1051/0004-6361/201527670

发表时间：

2015-12

期刊：

Astronomy and Astrophysics

影响因子：

6.5

通讯作者：

中科院分区：

物理与天体物理2区

文献类型：

作者：

G. Caminha;C. Grillo;P. Rosati;I. Balestra;W. Karman;M. Lombardi;A. Mercurio;M. Nonino;P. Tozzi;A. Zitrin;A. Biviano;M. Girardi;A. Koekemoer;Peter Melchior;M. Meneghetti;E. Munari;S. Suyu;K. Umetsu;M. Annunziatella;S. Borgani;T. Broadhurst;K. Caputi;D. Coe;C. Delgado-Correal;S. Ettori;A. Fritz;B. Frye;R. Gobat;C. Maier;A. Monna;M. Postman;B. Sartoris;S. Seitz;E. Vanzella;B. Ziegler

目标。我们用一组高精度的强透镜模型对星系团RXC J2 248.7−4431(z=0.348)的总质量分布进行了全面的研究，这些模型利用了许多多透镜系统的大量光谱信息。为了理解和量化参数强透镜模型的内在系统学，我们探索了22个模型的集合，在这些模型中，我们使用了多个图像族的不同样本，质量分布和宇宙学参数的不同参数化。作为强透镜模型的输入信息，我们使用了带有哈勃(CLASH)成像数据的星团透镜和超新星观测以及光谱后续观测，以及甚大望远镜上的可见光多目标光谱仪和多单元光谱探测器，以识别和表征真正的多图象族，并测量它们向下到mF814W≃26的红移。总共16个背景源，在红移范围1.0−6.1上，被倍增成47幅图像，其中24幅得到光谱确认，属于10个单独的源。其中还包括z=3.118的多透镜Lyman-α斑点。通过匹配透镜平面上多幅图像的观测位置，优化了模型中的星团总质量分布和基础宇宙学。采用贝叶斯马尔可夫链蒙特卡罗方法对最佳拟合参数的误差和协方差进行量化。我们表明，通过仔细选择大量光谱确认的多幅图像样本，最佳拟合模型可以在固定平坦的ΛCDM宇宙学中以0.3RMS散射值再现它们的观测位置，而缺乏光谱信息或使用不准确的光度红移可能导致模型参数值的偏差。我们发现，星系团总质量分布的最佳参数是由一个椭圆形的拟等温质量分布和截断的星系团星系的拟等温质量剖面组成。我们表明，通过向光谱族样本添加真正的光度选择的多幅图像，可以略微改善对模型参数的约束。特别是，我们发现，透镜总质量分布与宇宙基本几何之间的简并可以部分消除，这种简并是通过透镜与源之间的角径距离比来探测的。考虑到宇宙学参数随团簇参数的变化，我们发现(在68%置信度水平下)Ωm=0.25+0.13-0.16和w=−1.07+0.16-0.42对于w=Λ1和自由曲率的宇宙，Ωm=0.31+0.12-0.13和ΩΛ=0.38+0.38-0.27。最后，利用模拟多幅图像和星团总质量分布的玩具模型，我们估计视线质量结构对位置均方根的影响为0.3±0。我们认为，我们的透镜模型对宇宙学的明显敏感性是由于RXC J2248规则的势形，大量真实的多重图像，直到z=6.1，以及相对温和的介入大尺度结构的存在，正如我们的光谱调查所揭示的那样。

Aims. We perform a comprehensive study of the total mass distribution of the galaxy cluster RXC J2248.7−4431 (z = 0.348) with a set of high-precision strong lensing models, which take advantage of extensive spectroscopic information on many multiply lensed systems. In the effort to understand and quantify inherent systematics in parametric strong lensing modelling, we explore a collection of 22 models in which we use different samples of multiple image families, different parametrizations of the mass distribution and cosmological parameters.Methods. As input information for the strong lensing models, we use the Cluster Lensing And Supernova survey with Hubble (CLASH) imaging data and spectroscopic follow-up observations, with the VIsible Multi-Object Spectrograph (VIMOS) and Multi Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope (VLT), to identify and characterize bona fide multiple image families and measure their redshifts down to mF814W ≃ 26. A total of 16 background sources, over the redshift range 1.0−6.1, are multiply lensed into 47 images, 24 of which are spectroscopically confirmed and belong to ten individual sources. These also include a multiply lensed Lyman-α blob at z = 3.118. The cluster total mass distribution and underlying cosmology in the models are optimized by matching the observed positions of the multiple images on the lens plane. Bayesian Markov chain Monte Carlo techniques are used to quantify errors and covariances of the best-fit parameters.Results. We show that with a careful selection of a large sample of spectroscopically confirmed multiple images, the best-fit model can reproduce their observed positions with a rms scatter of 0.3 in a fixed flat ΛCDM cosmology, whereas the lack of spectroscopic information or the use of inaccurate photometric redshifts can lead to biases in the values of the model parameters. We find that the best-fit parametrization for the cluster total mass distribution is composed of an elliptical pseudo-isothermal mass distribution with a significant core for the overall cluster halo and truncated pseudo-isothermal mass profiles for the cluster galaxies. We show that by adding bona fide photometric-selected multiple images to the sample of spectroscopic families, one can slightly improve constraints on the model parameters. In particular, we find that the degeneracy between the lens total mass distribution and the underlying geometry of the Universe, which is probed via angular diameter distance ratios between the lens and sources and the observer and sources, can be partially removed. Allowing cosmological parameters to vary together with the cluster parameters, we find (at 68% confidence level) Ωm = 0.25+ 0.13-0.16 and w = −1.07+ 0.16-0.42 for a flat ΛCDM model, and Ωm = 0.31+ 0.12-0.13 and ΩΛ = 0.38+ 0.38-0.27 for a Universe with w = −1 and free curvature. Finally, using toy models mimicking the overall configuration of multiple images and cluster total mass distribution, we estimate the impact of the line-of-sight mass structure on the positional rms to be 0.3 ± 0. We argue that the apparent sensitivity of our lensing model to cosmography is due to the combination of the regular potential shape of RXC J2248, a large number of bona fide multiple images out to z = 6.1, and a relatively modest presence of intervening large-scale structure, as revealed by our spectroscopic survey.

CLASH-VLT: A highly precise strong lensing model of the galaxy cluster RXC J2248.7 - 4431 (Abell S1063) and prospects for cosmography

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