Astrophysics

A Precise Measurement of the Fermi-LAT Galactic Center Excess Morphology and Spectrum

Mattia Di Mauro

Featured May 26, 2026

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Simply

A new way to clean up messy space data from the Milky Way's center makes a mysterious gamma-ray glow much clearer, strongly suggesting it comes from dark matter rather than just regular stars.

In depth

The paper presents a novel multi-step fitting procedure and an iterative source-finding pipeline for *Fermi*-LAT data, significantly reducing systematic uncertainties in the Galactic Center region. This enhanced analysis enables a much more precise characterization of the Galactic Center Excess (GCE) morphology and spectrum, robustly distinguishing it from astrophysical backgrounds.

Key Takeaways

1
A new optimized multi-step fitting procedure substantially reduces systematic uncertainties in *Fermi*-LAT Galactic Center Excess (GCE) analysis, achieving fractional residuals of $≲ 10%$ .
2
The GCE morphology is robustly characterized as an approximately spherical generalized Navarro-Frenk-White (gNFW) profile with an inner slope $γ ≃ 1.15$ and a mild elongation.
3
The Dark Matter (DM)-motivated component of the GCE remains highly significant ( $\sim 28 - 120 σ$ ) across various interstellar emission models and analysis choices, even when astrophysical bulge-tracing templates are simultaneously included.

Conceptual Flow

HIGH LEVEL

Methodology: Sharpening the View of the Galactic Center

The scientists used a special multi-step process to clean up messy space data, making it much clearer to see the faint glow from the center of our galaxy.

Messy Space Data

Clean Up & Sort

Clearer Space Map

Results: Unveiling the Mysterious Glow

They found that the mysterious glow looks like a smooth, round cloud, which is what we'd expect if it came from invisible dark matter, rather than just regular stars.

Clearer Space Map

Measure Shape & Brightness

Dark Matter-like Glow