arXiv subjects

Leo Qiyuan Hu

Publications and source records attributed to Leo Qiyuan Hu.

2 recordsLinked to original sources

arXiv2026

The Origin of the Fermi Halo-like Emission: A New Model of the Fermi Bubbles

We study the gamma-ray sky at high latitudes for energies between 0.3 and 900 GeV. We search for a contribution in the high-latitude sky and in the region of the Galactic Stellar Halo that would be beyond known astrophysical emissions, i.e., the galactic diffuse emission, the isotropic mostly extragalactic gamma-ray background, the Fermi Bubbles, Loop I, the contribution from the Galactic Center Excess, and the known point and extended gamma-ray sources detected by the Fermi-LAT Collaboration. We perform a sequence of template fits to the Fermi gamma-ray data, testing different regions of interest of the galactic sky, utilizing a large set of alternative galactic diffuse emission models, and implementing alternative fitting schemes to assess the impact of increased modeling complexity of the gamma-ray sky. We find that the halo-like emission recently reported by Totani (2025) is real, but it is likely due to emission from the Fermi Bubbles rather than dark matter annihilation in the Galactic halo. We provide new templates for the Fermi Bubbles, including an updated model for the Flat Bubbles and a detailed model of their substructures, the Cocoons and the Inner Bubbles. In combination, these components account for the previously reported halo-like emission. We also estimate the associated fluxes and spectral properties of the Flat Bubbles, the Inner Bubbles, and the Cocoons. This updated model for the Fermi Bubbles provides new input toward understanding their origin.

astro-ph.HE↗

arXiv2026

Galactic Center gamma-ray excess from a generic triaxial halo

Recent studies of Galactic surveys, such as Gaia, have revealed that the Milky Way's gravitational potential comes from a matter distribution that is triaxial and rotated with respect to the Galactic center-Sun axis. This, in turn, could mean that the dark matter halo also shares these properties. In this work, by fitting to the Fermi-LAT gamma-ray observations, we test the compatibility of the morphology of the Galactic Center Excess (GCE) from dark matter annihilation with a triaxial dark matter halo. In particular, we consider both untilted triaxial halos and halos whose principal axes are tilted with respect to the Galactic disk. In our fits of the Fermi-LAT data, by testing over a large library of galactic diffuse emission models, we quantify how the halo triaxiality and tilt affect the line-of-sight-integrated annihilation signal and, consequently, the preferred GCE spatial templates. We find that the GCE spectrum and inner cuspiness are robust against variations in the triaxiality and tilt of the dark matter halo. However, in terms of its overall morphology, the GCE in the gamma-ray data can discriminate between choices for the dark matter halo's triaxiality and tilt. Finally, we find that the GCE is more compatible with originating from a triaxial and tilted halo of dark matter than originating from a triaxial and tilted halo of stars, a result important for understanding the GCE's origin.

astro-ph.HE↗