Research Highlight

Gravitational lensing due to minivoids and minifilaments

When a celestial object (such as a galaxy) lies along the line-of-sight to a more distant object (such as a quasar), the gravitational field of the former refracts the light of the latter,  resulting in deformation or splitting of light into multiple images (called 'gravitational lensing'). Usually, we assume that the dark matter surrounding a lensing galaxy has a spherical or an ellipsoidal shape. However,  objects such as voids and filaments in the line-of-sight to the light source may also contribute to lensing. I have studied the lensing effects of minivoids and minifilaments whose mass scales are comparable to those of dwarf galaxies, and found that the flux ratios of lensed images in a lensed quasar MG0414+0534 can be explained by a minivoid or a minifilament in intergalactic spaces. In the near future, we would be able to observe such mini-structures with a length scale of 5~50 kpc and a mass scale of 10^8 to 10^9 solar mass (2015 MNRAS, Vol. 447, issue 2, p1452-1459).

Surface mass density of the best-fit lens model (lensing galaxy (upper left), subhalo (upper right) , filament (lower left), void (lower right). A1,A2, B, C indicate the positions of lensed images in MG0414+0534. There is an anomaly in the flux of A2.