B. Thakore, Università degli Studi di Torino
M. Negro, Louisiana State University
M. Regis, Università degli Studi di Torino
S. Camera, Università degli Studi di Torino
D. Gruen, Ludwig-Maximilians-Universität München
N. Fornengo, Università degli Studi di Torino
A. Roodman, SLAC National Accelerator Laboratory
A. Porredon, Ruhr-Universitat Bochum
T. Schutt, SLAC National Accelerator Laboratory
A. Cuoco, Università degli Studi di Torino
A. Alarcon, CSIC - Instituto de Ciencias del Espacio (ICE)
A. Amon, Princeton University
K. Bechtol, UW-Madison College of Engineering
M. Becker, Argonne National Laboratory
G. Bernstein, University of Pennsylvania
A. Campos, Carnegie Mellon University
A. Carnero Rosell, Instituto Astrofisico de Canarias
M. Carrasco Kind, University of Illinois Urbana-Champaign
R. Cawthon, William Jewell College
C. Chang, The Department of Astronomy and Astrophysics, The University of Chicago
R. Chen, Duke University
A. Choi, NASA Goddard Space Flight Center
J. Cordero, The University of Manchester
C. Davis, Kavli Institute for Particle Astrophysics and Cosmology
J. DeRose, Lawrence Berkeley National Laboratory
H. Diehl, Fermi National Accelerator Laboratory
S. Dodelson, The Department of Astronomy and Astrophysics, The University of Chicago
C. Doux, University of Pennsylvania
A. Drlica-Wagner, The Department of Astronomy and Astrophysics, The University of Chicago
K. Eckert, University of Pennsylvania
J. Elvin-Poole, University of Waterloo
S. Everett, California Institute of Technology
A. Ferté, SLAC National Accelerator Laboratory

Document Type

Article

Publication Date

6-1-2025

Abstract

Our understanding of the γ-ray sky has improved dramatically in the past decade, however, the unresolved γ-ray background (UGRB) still has a potential wealth of information about the faintest γ-ray sources pervading the Universe. Statistical cross-correlations with tracers of cosmic structure can indirectly identify the populations that most characterize the γ-ray background. In this study, we analyze the angular correlation between the γ-ray background and the matter distribution in the Universe as traced by gravitational lensing, leveraging more than a decade of observations from the Fermi-Large Area Telescope (LAT) and 3 years of data from the Dark Energy Survey (DES). We detect a correlation at signal-to-noise ratio of 8.9. Most of the statistical significance comes from large scales, demonstrating, for the first time, that a substantial portion of the UGRB aligns with the mass clustering of the Universe as traced by weak lensing. Blazars provide a plausible explanation for this signal, especially if those contributing to the correlation reside in halos of large mass (∼ 1014 M ⊙) and account for approximately 30-40% of the UGRB above 10 GeV. Additionally, we observe a preference for a curved γ-ray energy spectrum, with a log-parabolic shape being favored over a power-law. We also discuss the possibility of modifications to the blazar model and the inclusion of additional γ-ray sources, such as star-forming galaxies, misalinged active galactic nuclei, or particle dark matter.

Publication Source (Journal or Book title)

Journal of Cosmology and Astroparticle Physics

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