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arXiv 1209.2709astro-ph.CO
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预测下一代空间宽场巡天中预期的巨型弧的数量

Predicting the number of giant arcs expected in the next generation wide-field surveys from space

Michele Boldrin, Carlo Giocoli, Massimo Meneghetti, Lauro Moscardini

摘要:

在本文中,我们估计了在一个宽视场的调查,如将由欧几里得空间任务,假设一个ΛCDM宇宙学操作的引力弧可检测的数量。我们使用公开可用的代码MOKA模拟引力透镜获得现实的偏转角地图。通过光线跟踪代码处理这些图,以估计每个透镜的强透镜效应截面。我们的方法包括:1)产生一个光锥,它是由理论质量函数绘制的透镜填充的; 2)使用具有NFW的三轴光晕对每个单个透镜进行建模(Navarro-Frenk-White)密度分布和理论浓度-质量关系,包括子结构,3)确定作为光锥中每个透镜的红移的函数的透镜化截面,(4)模拟模拟观测以表征在欧几里德图像中可检测的源的红移分布。我们重点研究了所谓的巨型弧,即以大长宽比(l/w > 5,7.5和10)为特征的引力弧。我们量化的电弧可检测性在不同的显着性以上的水平的背景。执行128个不同的实现15,000平方米。度调查,我们发现当l/w>5,7.5和10时,在局部背景以上1σ处可检测到的弧数分别为8912,2914和1275。对于高于背景水平3σ的检测限,预期弧数降至2409、790和346。从我们的分析中,我们发现,大部分的透镜,有助于透镜的光学深度位于红移0.4&lt;zl <0.7 and that the 50% of the arcs are images of sources at zs >3。这是欧几里德观测到的强透镜群的完整特征的第一步。[删节]

英文摘要:

In this paper we estimate the number of gravitational arcs detectable in a wide-field survey such as that which will be operated by the Euclid space mission, assuming a ΛCDM cosmology. We use the publicly available code MOKA to obtain realistic deflection angle maps of mock gravitational lenses. The maps are processed by a ray-tracing code to estimate the strong lensing cross sections of each lens. Our procedure involves 1) the generation of a light-cone which is populated with lenses drawn from a theoretical mass-function; 2) the modeling of each single lens using a triaxial halo with a NFW (Navarro-Frenk-White) density profile and theoretical concentration-mass relation, including substructures, 3) the determination of the lensing cross section as a function of redshift for each lens in the light-cone, 4) the simulation of mock observations to characterize the redshift distribution of sources that will be detectable in the Euclid images. We focus on the so-called giant arcs, i.e. gravitational arcs characterized by large length-to-width ratios (l/w > 5, 7.5 and 10). We quantify the arc detectability at different significances above the level of the background. Performing 128 different realizations of a 15,000 sq. degree survey, we find that the number of arcs detectable at 1σ above the local background will be 8912,2914, and 1275 for l/w>5, 7.5 and 10, respectively. The expected arc numbers decrease to 2409, 790, and 346 for a detection limit at 3σ above the background level. From our analysis, we find that most of the lenses which contribute to the lensing optical depth are located at redshifts 0.4<zl<0.7 and that the 50% of the arcs are images of sources at zs > 3. This is the first step towards the full characterization of the population of strong lenses that will be observed by Euclid. [abridged]

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