发表机构
University of Minnesota; UHasselt; Indian Institute of Science Bangalore; Aix Marseille Univ; Max Planck Institute for Extraterrestrial Physics; Max-Planck-Institut für Astrophysik（明尼苏达大学; 荷语哈瑟尔特大学; 印度科学研究所班加罗尔分校; 艾克斯-马赛大学; 马克斯·普朗克地外物理研究所; 马克斯·普朗克天体物理研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文通过解析方法研究星系团透镜质量图中的形状简并，指出其是不同技术重建质量图差异的可能原因，且在图像密集区域被抑制，对时间延迟影响通常约1%，特定源可达10%。
AI 中文摘要
星系团的天球投影质量分布被广泛用于约束暗物质的粒子性质、放大高红移背景星系的光通量和角尺度，并构建其光度函数直至难以或无法达到的暗绝对星等。因此，获得精确且准确的星系团质量图对这些研究至关重要。然而，对同一星系团的任意两张质量图进行目视检查表明，其等密度轮廓的形状在<30kpc尺度上往往在细节上不相似，且两者之间没有简单的关系。这些差异源于重建中的系统不确定性，而这又源于透镜简并。然而，常见的简并，如质量片简并或源位置变换，无法解释这些差异中的大部分，这意味着更广义的形状简并是原因。在本文中，我们使用解析方法研究形状简并。我们得出三个主要结论：（i）形状简并可能是不同技术恢复的星系团透镜质量图差异的可能原因。（ii）在透镜面上具有紧密成组的透镜图像的区域中，形状简并被显著抑制。（iii）在图像数量多的星系团中，如MACS J0416，它们对来自同一源的图像之间时间延迟的影响通常较小，约为1%，但对于某些多重成像的背景源，影响可达约10%，从而影响H_0的测定。
英文摘要
Sky-projected mass distributions of galaxy clusters are widely used to constrain particle properties of dark matter, to magnify in flux and angular extent high redshift background galaxies, and to construct their luminosity function down to faint absolute magnitudes that are otherwise hard or impossible to reach. Obtaining accurate and precise mass maps of clusters is therefore of central importance for these studies. Yet, a visual inspection of any two mass maps of the same cluster shows that the shapes of their isodensity contours are often dissimilar in detail on <30kpc scales, and there is no simple relation connecting the two. These differences are due to systematic uncertainties in reconstructions, which are in turn due to lensing degeneracies. However, commonly known degeneracies, like the mass sheet degeneracy or the source position transformation cannot account for most of these differences, implying that more generalized shape degeneracies are responsible. In this paper we study shape degeneracies using an analytical approach. We conclude with three main takeaways: (i) Shape degeneracies are the likely cause of differences in the mass maps of cluster lenses recovered by different techniques. (ii) Shape degeneracies are significantly suppressed in regions of the lens plane that have tight groupings of lensed images. (iii) In clusters where image numbers are high, such as MACS J0416, their effect on time delays between images from the same source are generally small, of order 1%, but can reach ~10% for some multiply imaged background sources, affecting the determination of H_0.
Comments15 pages, 9 figures, submitted to OJA
