Research Highlight

Anomalous flux ratios due to line-of-sight mini-structures?

Image positions in some QSO-galaxy quadruple lens systems can be well fit by simple smooth galaxy mass
models whereas observed flux ratios are more difficult to match. This mismatch is called ``flux-ratio anomaly'', which
has long been veiled in great mystery.  Using N-body and ray-tracing simulations, we found that such anomalies detected in mid-infrared bands can be explained by the weak lensing effects due to mini-structures (halos and voids) in intergalactic spaces without taking into account subhalos in the lensing galaxy. The typical mass scale of such structure is of the order of 10^8 solar mass per arcsec^2. The result is consistent with our semi-analytic result based on the power spectrum  obtained from N-body simulations. For detail, see http://arxiv.org/abs/1308.4855

     (From Takahashi & Inoue 2014, MNRAS DOI:10.1093/mnras/stu328  eta describes the mean magnification perturbation marginalized over the 4-images due to line-of-sight structures. )