2026/08/04 by Wen-Qing Guo
Physics and Astronomy · #astro-ph.HE
16 pages, 3 figures
arxiv created 2026/08/04 · arxiv updated 2026/08/05
Axion-like particles (ALPs) provide a well-motivated dark matter candidate whose interactions with Standard Model particles may generate observable cosmological signatures. We investigate the diffuse γ-ray emission produced by the scattering process between ALP dark matter and cosmic-ray (CR) protons inside dark matter halos, and explore its detectability through the cross-correlation between the unresolved γ-ray background (UGRB) measured by Fermi Large Area Telescope (LAT) and the Two Micron All Sky Survey Redshift Survey (2MRS) galaxy catalog in the local Universe (z≤0.1). To model the cosmological GeV-PeV CR proton population, we develop a phenomenological bottom-up prescription that links CR injection to the star formation rate through the supernova rate, while the steady-state CR density is determined by diffusive escape. Our forecasts indicate that UGRB-galaxy cross-correlation measurements can probe previously unexplored regions of the ALP parameter space over a broad range of ALP masses. More generally, this work presents a general framework for cosmological observables generated by interactions between dark matter and an additional astrophysical field, opening a new avenue for indirect dark matter searches using large-scale structure observations.