Center for Theoretical Physics of the Universe (CTPU-PTC)

Constraining Dark Matter Annihilation with Large-Scale Structures

by Dr Masato Shirasaki (NAOJ)

An array of astronomical observations over a wide range of redshifts and length scales consistently support the existence of cosmic dark matter (DM). Although the abundance of cosmic DM has been constrained in previous cosmological analyses, the microscopic nature of DM still remains un! known. The extragalactic gamma-ray background (EGB) is thought to be a potential probe of DM, if DM annihilates or decays to produce high-energy photons. Although the mean EGB intensity can be explained by unresolved astrophysical sources, the anisotropy in the diffuse gamma-ray sky contains, in principle, rich information about any unresolved DM source contributions. This is because the DM density distribution in the Universe is expected to be highly inhomogeneous due to the non-linear gravitational growth of structure. Therefore, any observational tracers of the DM distribution should correlate with the extragalactic gamma-ray map. In this talk, I will review the recent progress of the cross-correlation of the EGB with large-scale structures (LSS) as a probe of DM annihilation. Then, I will talk about our measurement of cross correlations of the EGB with gravitational lensing effects of distant galaxies and discuss our constraints on DM annihilation.