http://arxiv.org/abs/1802.10257
The extragalactic $\gamma$-ray background (EGB) arises from accumulation $\gamma$-ray emissions from resolved and unresolved extragalactic sources as well as diffuse processes. It is important to understand the origin of the EGB in the context of cosmological structure formation. Known astrophysical $\gamma$-ray sources such as blazars, star-forming galaxies, and radio galaxies are expected to trace the underlying cosmic matter density distribution. We explore the correlation of the EGB from Fermi-LAT data with the large-scale matter density distribution from the Subaru Hyper Suprime-Cam (HSC) SSP survey. We reconstruct an unbiased surface matter density distribution $\kappa$ at $z<1$ by applying weak-gravitational lensing analysis to the first-year HSC data. We then calculate the $\kappa – \gamma$ cross-correlation. Our measurement suggests overall weak correlation at angular scales of 30-60 arcmin. The result is essentially consistent with a null detection, and allows us to derive constraints on the statistical relationships between astrophysical $\gamma$-ray sources and dark matter halos. We make forecasts for the detectability of the cross-correlation in the final HSC data. Detection with a $\sim3\sigma$ confidence can be achieved with the full survey covering 1,400 squared degrees planned for HSC SSP.
M. Shirasaki, O. Macias, S. Horiuchi, et. al.
Thu, 1 Mar 18
1/66
Comments: 17 pages, 9 figures, 4 tables, to be submitted to Physical Review D
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