SUBARU MID-INFRARED IMAGING OF THE QUADRUPLE LENSES. II. UNVEILING LENS STRUCTURE OF MG0414+0534 AND Q2237+030
SUBARU MID-INFRARED IMAGING OF THE QUADRUPLE LENSES. II. UNVEILING LENS STRUCTURE OF MG0414+0534 AND Q2237+030
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DOI：
10.1088/0004-637x/697/1/610
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发表时间：
2009-03
期刊：
影响因子：
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通讯作者：
T. Minezaki;Masashi Chiba;N. Kashikawa;K. T. Inoue;H. Kataza
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作者：
T. Minezaki;Masashi Chiba;N. Kashikawa;K. T. Inoue;H. Kataza
利用Subaru望远镜上安装的冷却式中红外相机和光谱仪，对MG 0414 +0534和Q 2237 +030四重透镜系统进行了11.7 μm的中红外成像。MG 0414 +0534的特征在于一对明亮的透镜图像（A1，A2），并且它们的光通量比A2/A1显著偏离光滑透镜模型的预测。Q2237+030是“爱因斯坦十字”，由四个透镜图像组成，它们受到前景透镜星系中微透镜的显著影响。我们对这些透镜图像的中红外观测表明，MG 0414 +0534的A2/A1的中红外通量比几乎为1（0.90 ± 0.04）。我们发现，这个流量比是系统的小，在4-5σ水平，与预测的最佳光滑透镜模型（1.09）由一个奇异的等温椭球和外部剪切。光滑透镜模型还考虑了可能的微弱卫星（物体X）的额外透镜效应，仍然提供了A2/A1=1.06的大通量比，从而表明存在更多可以解释我们的观测结果的子结构。相比之下，对于Q2237+030，我们的高信噪比观测表明，Q2237+030的所有四张图像之间的中红外通量比实际上与光滑透镜模型的预测一致。基于这些类星体的核心周围的尘埃环的大小估计，我们设置在这些透镜系统，这可能会导致异常的流量比的子结构的质量限制。对于MG 0414 +0534，由于在爱因斯坦半径内的子结构所需的质量是10360 M，因此冷暗物质子结构的毫透镜效应是最有可能的。如果它被建模为一个奇异的等温球，半径为100 pc的内部质量为100 × 105 M。对于Q2237+030，没有明显的千透镜效应的证据，所以报告的短波长异常流量比完全是由恒星的微透镜效应引起的。
We present mid-infrared imaging at 11.7 μm for the quadruple lens systems, MG0414+0534 and Q2237+030, using the cooled mid-infrared camera and spectrometer attached on the Subaru telescope. MG0414+0534 is characterized by a bright pair of lensed images (A1, A2) and their optical flux ratio A2/A1 deviates significantly from the prediction of a smooth-lens model. Q2237+030 is “the Einstein Cross” being comprised of four lensed images, which are significantly affected by microlensing in a foreground lensing galaxy. Our mid-infrared observations of these lensed images have revealed that the mid-infrared flux ratio for A2/A1 of MG0414+0534 is nearly unity (0.90 ± 0.04). We find that this flux ratio is systematically small, at 4–5σ level, compared with the prediction of a best smooth-lens model (1.09) represented by a singular isothermal ellipsoid and external shear. The smooth-lens model, which also considers the additional lensing effect of the possible faint satellite, object X, still provides a large flux ratio of A2/A1=1.06, thereby suggesting the presence of more substructures that can explain our observational result. In contrast, for Q2237+030, our high signal-to-noise observation indicates that the mid-infrared flux ratios between all the four images of Q2237+030 are virtually consistent with the prediction of a smooth-lens model. Based on the size estimate of the dust torus surrounding the nuclei of these QSOs, we set limits on the mass of a substructure in these lens systems, which can cause anomalies in the flux ratios. For MG0414+0534, since the required mass of a substructure inside its Einstein radius is ≳360 M☉, millilensing by a cold dark matter substructure is most likely. If it is modeled as a singular isothermal sphere, the mass inside a radius of 100 pc is given as ≳1.0 × 105 M☉. For Q2237+030, there is no significant evidence of millilensing, so the reported anomalous flux ratios in shorter wavelengths are entirely caused due to microlensing by stars.