标题： MG1131+0456透镜星系的质量分布 显示英文标题

标题： The Mass Distribution of the Lens Galaxy in MG1131+0456

摘要： 我们展示了使用LensClean算法对引力透镜MG1131+0456在5 GHz、8 GHz和15 GHz的图像进行建模的结果。 对透镜中的质量分布进行了两种模型拟合：一种是de Vaucouleurs模型，另一种是二维势函数phi = b^{2-阿尔法}(r^2+s^2)^{$\alpha$/2}/2alpha模型，这两种模型都处于外部剪切场中。 最佳拟合的de Vaucouleurs模型的有效半径为R\_e = 0.83±0.13弧秒，比在光学波长下测量的值大。 最佳拟合的“alpha模型”具有alpha=0.6±0.2和核心半径s = 0.19 ± 0.07弧秒。 等温模型（alpha=1）与数据不符。 最佳的alpha模型显著优于最佳的de Vaucouleurs模型，能更好地拟合8 GHz的图像。 尽管难以通过视觉区分原始图像和重建图像，但没有一个模型在统计上与数据一致。 我们认为主要问题是外部剪切不足以作为透镜星系角结构的模型。 模型中的有限核心半径是由扩展环的结构决定的，因此我们确认8 GHz图像中的中心成分是源的中心、透镜化图像，而不是透镜星系。 模型透镜位置、剪切的位置角以及环内部的质量由透镜模型非常精确地确定。 紧凑成分之间的时间延迟预测的不确定性我们估计最多为±9\%，形式上的不确定性为±4\%。 显示英文摘要

摘要： We present the results of modeling 5, 8 and 15 GHz maps of the gravitational lens MG1131+0456 using the LensClean algorithm. Two models for the mass distribution in the lens were fit: a de Vaucouleurs model and a model with the two-dimensional potential phi = b^{2-alpha}(r^2+s^2)^{alpha/2}/2alpha, both in an external shear field. The best fit de Vaucouleurs model has an effective radius of R_e = 0.83+-0.13 arcseconds, larger than that measured at optical wavelengths. The best fit ``alpha model'' has alpha=0.6+-0.2 and a core radius of s = 0.19 +- 0.07 arcseconds. An isothermal model (alpha=1) is inconsistent with the data. The best alpha model fits the 8 GHz map significantly better than the best de Vaucouleurs model. Although it is difficult to distinguish visually the original image and the reconstructions, none of the models is statistically consistent with the data. We believe the primary problem is that an external shear is an inadequate model for the angular structure of the lens galaxy. The finite core radius in the models is required by the structure of the extended ring, so we confirm that the central component in the 8 GHz map is a central, lensed image of the source rather than the lens galaxy. The model lens positions, the position angle of the shear, and the mass interior to the ring are determined very precisely by the lens models. The time delay between the compact components is predicted with an uncertainty we estimate to be at most +- 9%; the formal uncertainty is +- 4%.