Subaru Mid-Infrared Imaging of the Quadruple Lenses PG 1115+080 and B1422+231: Limits on Substructure Lensing
Subaru Mid-Infrared Imaging of the Quadruple Lenses PG 1115+080 and B1422+231: Limits on Substructure Lensing
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DOI：
10.1086/430403
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发表时间：
2005-03
期刊：
影响因子：
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通讯作者：
M. Chiba;T. Minezaki;N. Kashikawa;H. Kataza;K. T. Inoue
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作者：
M. Chiba;T. Minezaki;N. Kashikawa;H. Kataza;K. T. Inoue
我们展示了四倍镜系统 PG 1115+080 和 B1422+231 的 11.7 μm 中红外成像，使用安装在斯巴鲁望远镜上的冷却中红外相机和光谱仪 (COMICS)。这些透镜 QSO 的特点是其异常的光学和无线电通量比，分别是从 PG 1115+080 的 A1 和 A2 图像以及 B1422+231 的 A、B 和 C 图像获得的，即，这样的通量比很难通过具有平滑质量分布的透镜模型来再现。我们对这些图像的中红外观测表明，PG 1115+080 的中红外通量比 A2/A1 实际上与光滑透镜模型一致（但与光通量比不一致），而对于 B1422+231，A、B、C 图像之间的中红外通量比与无线电通量比非常一致。我们还在这些 QSO 的光谱能量分布中发现了明显的红外凸起，从而表明观察到的中红外通量源自 QSO 核周围的热尘埃环。根据尘埃环面的尺寸估计，我们对这些透镜系统中的子结构的质量进行了限制，从而导致异常的光学或无线电通量比。对于 PG 1115+080，爱因斯坦半径 ME 内子结构的质量为 ≲16 M☉，如果建模为奇异等温球 (SIS)，则对应于半径 100 pc 内质量为 M ≲ 2.2 × 104 M☉ 的恒星或低质量 CDM 子晕。对于 B1422+231，我们得到 ME ≳ 209 M☉，表明 CDM 子晕的可能性更大，质量为 M ≳ 7.4 × 104 M☉。
We present mid-infrared imaging at 11.7 μm for the quadruple lens systems PG 1115+080 and B1422+231 using the cooled mid-infrared camera and spectrometer (COMICS) attached on the Subaru Telescope. These lensed QSOs are characterized by their anomalous optical and radio flux ratios, as obtained for A1 and A2 images of PG 1115+080 and A, B, and C images of B1422+231, respectively, i.e., such flux ratios are hardly able to be reproduced by lens models with a smooth mass distribution. Our mid-infrared observations for these images have revealed that the mid-infrared flux ratio A2/A1 of PG 1115+080 is virtually consistent with smooth lens models (but inconsistent with the optical flux ratio), whereas for B1422+231, the mid-infrared flux ratios among the A, B, and C images are in good agreement with the radio flux ratios. We also identify a clear infrared bump in the spectral energy distributions of these QSOs, thereby indicating that the observed mid-infrared fluxes originate from a hot dust torus around a QSO nucleus. Based on the size estimate of the dust torus, we place limits on the mass of a substructure in these lens systems causing the anomalous optical or radio flux ratios. For PG 1115+080, the mass of a substructure inside an Einstein radius ME is ≲16 M☉, corresponding to either a star or a low-mass CDM subhalo having a mass of M ≲ 2.2 × 104 M☉ inside a radius of 100 pc if modeled as a singular isothermal sphere (SIS). For B1422+231, we obtain ME ≳ 209 M☉, indicating that a CDM subhalo is more likely, having a mass of M ≳ 7.4 × 104 M☉.