Date : 2/22 (Wed) [15:00 - 17:00] @ F313
Speaker: Prof. Kaiki Inoue (Kinki University)
Title : Probing Dark Dwarf Galaxies with Gravitational Lensing
Abstract: The so-called 'missing satellite problem' is one of the most challenging problem in the modern astrophysics: Theory predicts an excess number of dark subhalos around the Milky Way than observed satellite galaxies, which are expected to trace them. If theory is correct, we expect a number of dark dwarf galaxies in the universe. Since dark dwarf galaxies are faint, the methods for detecting such objects are limited to either a direct detection of a faint signal or the gravitational lensing effect, bending of light rays passing by massive objects. In fact, several quasar-galaxy quadruply lensed systems have been known to show 'anomaly' in the flux ratios: The flux ratios of lensed images disagree with the prediction of best-fit lens models with a smooth potential whose fluctuation scale is larger than the separation between the lensed images. It has been considered as an imprint of cold dark matter subhalos, but recent works by our groups and others indicate that intervening halos and voids in the line-of-sight are important as well as subhalos. In this talk, I review previous our works on 'substructure lensing' caused by subhalos and intervening structures, and present our recent observational results obtained from ALMA submillimeter observations of a SMG-galaxy and a quasar-galaxy lens systems and their implications and future prospects.

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