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arXiv 1108.0678astro-ph.CO
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CASSOWARY 5强透镜系统中的富暗物质早型星系

Dark matter-rich early-type galaxies in the CASSOWARY 5 strong lensing system

C. Grillo, L. Christensen

摘要:

我们研究了CASSOWARY巡天发现的5号强引力透镜系统。在这个系统中,一个红移为1.069的源被两个红移为0.388的早型星系透镜化为四个探测图像。所观察到的多个图像的位置被很好地再现了一个模型,在该模型中的偏转器的总质量分布描述在两个奇异的等温球轮廓。通过模拟透镜星系的光谱能量分布,我们测量透镜发光质量和恒星的质光比。这些值用于解开多个图像附近的发光和暗物质分量。我们估计,在以主透镜为中心的圆柱体内投影的黑暗与总质量之比为0.8 +/- 0.1,半径为12.6 kpc。我们将这些测量结果与孤立透镜星系中在相似距离(有效半径单位)处发现的典型值进行对比,结果表明,这些透镜星系中存在的暗物质的量几乎是具有可比发光质量的场透镜星系的四倍。因此,数据和模型与将该系统的透镜解释为星系群是一致的。我们推断,这些星系中的过密环境和暗物质浓度一定影响了透镜发光质量组分的组装。我们的结论是,进一步多诊断分析星系群的内部属性有可能为我们提供一个独特的洞察复杂的重子和暗物质物理学的相互作用,规则的宇宙结构的形成。

英文摘要:

We study the strong gravitational lensing system number 5 identified by the CASSOWARY survey. In this system, a source at redshift 1.069 is lensed into four detected images by two early-type galaxies at redshift 0.388. The observed positions of the multiple images are well reproduced by a model in which the total mass distribution of the deflector is described in terms of two singular isothermal sphere profiles. By modelling the lens galaxy spectral energy distributions, we measure the lens luminous masses and stellar mass-to-light ratios. These values are used to disentangle the luminous and dark matter components in the vicinity of the multiple images. We estimate that the dark over total mass ratio projected within a cylinder centred on the primary lens and with a radius of 12.6 kpc is 0.8 +/- 0.1. We contrast these measurements with the typical values found at similar distances (in units of the effective radius) in isolated lens galaxies and show that the amount of dark matter present in these lens galaxies is almost a factor four larger than in field lens galaxies with comparable luminous masses. Data and models are therefore consistent with interpreting the lens of this system as a galaxy group. We infer that the overdense environment and dark matter concentration in these galaxies must have affected the assembly of the lens luminous mass components. We conclude that further multi-diagnostics analyses on the internal properties of galaxy groups have the potential of providing us a unique insight into the complex baryonic and dark-matter physics interplay that rules the formation of cosmological structures.

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