SUBARU MID-INFRARED IMAGING OF THE QUADRUPLE LENSES. II. UNVEILING LENS STRUCTURE OF MG0414+0534 AND Q2237+030
- Institute of Astronomy, School of Science, University of Tokyo, Mitaka, Tokyo 181-0015 (Japan)
- Astronomical Institute, Tohoku University, Aoba-ku, Sendai 980-8578 (Japan)
- National Astronomical Observatory, Mitaka, Tokyo 181-8588 (Japan)
- School of Science and Engineering, Kinki University, Higashi Osaka 577-8502 (Japan)
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Kanagawa 229-8510 (Japan)
We present mid-infrared imaging at 11.7 {mu}m 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 4-5{sigma} 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 {approx}>360 M {sub sun}, 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 {approx}>1.0 x 10{sup 5} M {sub sun}. 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.
- OSTI ID:
- 21300557
- Journal Information:
- Astrophysical Journal, Vol. 697, Issue 1; Other Information: DOI: 10.1088/0004-637X/697/1/610; Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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