Oral Presentation

Searching for Dark Structures: A Comparison of Weak Lensing Convergence Maps and Lensing-Weighted Galaxy Density Maps

Author(s): Soojin Kim (Astronomy Program, Department of Physics and Astronomy, Seoul National University) Ho Seong Hwang (Astronomy Program, Department of Physics and Astronomy, Seoul National University / SNU Astronomy Research Center, Seoul National University / Australian Astronomical Optics - Macquarie University) Niall Jeffrey (Department of Physics and Astronomy, University College London)

Presenter: Soojin Kim (Seoul National University)

Dark matter plays a crucial role in the formation of large-scale structures in the standard cosmological model, yet its true nature and distribution remain elusive. Although galaxies trace the large-scale structures in the universe, a substantial portion of dark matter may exist without associated visible galaxies. In this work, we compare the dark matter distribution inferred from weak gravitational lensing with the observed galaxy distribution to identify ‘dark structures’ with a high dark matter-to-galaxy density ratio. To do that, we use weak lensing convergence maps from the Dark Energy Survey Year 3 data, and construct corresponding galaxy convergence maps at z<~1.0. The galaxy convergence maps represent galaxy number density fluctuations weighted by lensing efficiency. We find the overall agreement between the two maps. However, we identify 22 regions where the dark matter density significantly exceeds the galaxy density. After carefully examining survey depth, proximity to survey boundaries, and spatial correspondence with convergence peaks, we select seven of the most probable candidates for dark structures. This sample provides valuable testbeds for further studies of dark matter mapping. Moreover, our method will be useful to identify dark structures in upcoming large-scale weak lensing surveys, such as the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST) and the Nancy Grace Roman Telescope.