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arXiv 2006.09391astro-ph.GAastro-ph.CO
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四重成像超新星iPTF16geu中透镜星系的两分量质量模型

Two-component mass models of the lensing galaxy in the quadruply imaged supernova iPTF16geu

Liliya L. R. Williams, David Zegeye

摘要:

第一个解析的、多重成像的Ia型超新星iPTF16geu是在4年前观测到的,距离这种系统首次设想已经过去了50年。由于源的独特性质,这些系统在研究星系结构和宇宙学参数方面有很大的希望。然而,这个第一个例子给建模者带来了一些困惑。为了解释图像通量,需要恒星微透镜效应的贡献,但为了适应微透镜效应的大小,椭圆幂律透镜模型的密度斜率必须非常浅,即$ρ_{2D} \propto r^{-0.7}$。此外,质心必须从观察到的光的中心偏移约0.1 kpc,并且光分布的位置角与质量的位置角偏离约40度。在本文中,我们提出了解决前两个问题的质量模型,并提出了第三个解决方案。受局部椭圆星系观测和最近对星系尺度透镜的分析的启发,我们的质量模型由两个偏置(重子)质量分量组成。由此产生的质量分布有一个单一的质心,但不平衡,并具有等密度轮廓,不是纯粹的椭圆形,不自相似的半径。对于我们的许多模型来说,微透镜的要求是适度的,并且由扩展的超新星宿主星系形成的环类似于观察到的环。

英文摘要:

The first resolved, multiply imaged supernova Type Ia, iPTF16geu, was observed 4 years ago, five decades after such systems were first envisioned. Because of the unique properties of the source, these systems hold a lot of promise for the study of galaxy structure and cosmological parameters. However, this very first example presented modelers with a few puzzles. It was expected that to explain image fluxes a contribution from microlensing by stars would be required, but to accommodate the magnitude of microlensing, the density slope of the elliptical power law lens model had to be quite shallow, $ρ_{2D} \propto r^{-0.7}$. Furthermore, the center of mass had to be displaced from that of observed light by ~0.1 kpc, and the position angle of light distribution was misaligned with that of mass by ~40 degrees. In this paper we present mass models that resolve the first two problems, and suggest a resolution of the third. Motivated by observations of local ellipticals, and some recent analysis of galaxy-scale lenses, our mass models consist of two offset (baryonic) mass components. The resulting mass distributions have a single centroid, but are lopsided, and have isodensity contours that are not purely elliptical and not self-similar with radius. For many of our models the microlensing requirements are modest, and the ring formed by the extended supernova host galaxy resembles the observed one.

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