Speaker
Dr
Manuel Colavincenzo
(University of Turin)
Description
We report the identification of a positive cross-correlation signal between the unresolved $\gamma$-ray emission, measured by the Fermi Large Area Telescope, and four different galaxy cluster catalogues: WHY18 (infrared galaxies), SDSSDR9 (optical galaxies), MCXCsub and HIFLUGCS (X-ray galaxies). When confronted with a model that traces the Large Scale Structure contribution to the unresolved extragalactic $\gamma$-ray emission in terms of Active Galactic Nuclei, the analysis rejects the no-signal hypothesis with a significance larger than $2\sigma$ for WHY18, SDSSDR9 and HIFLUGCS, raised to $4\sigma$ for the MCXCsub catalog. For the most significant case of MCXCsub, we also obtain that a sizeable fraction of the correlation signal seems to originate from the more extended objects, thus intriguingly suggesting a possible contribution from the Intra Cluster Medium (ICM). Current statistics are nevertheless unable to firmly assess an ICM origin of this excess. The same cluster catalogues are also used to detect bounds on the mass of the Dark Matter within the WIMP paradigm. The analysis has been performed by introducing an accurate estimation of the power spectrum covariance matrix, built with mock realisations of the gamma and galaxy cluster maps, which allows a precise statistical evaluation of the significance of the measured angular power spectrum.
Primary author
Dr
Manuel Colavincenzo
(University of Turin)
