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Updated: Sep 2, 2026

Measurement and Analysis of Atomic Hydrogen and Diatomic Molecular AlO, C2, CN, and TiO Spectra Following Laser-induced Optical Breakdown
Published on: February 14, 2014
Search for Dark Matter Annihilation and Decay with Hα Line Emission
1Kavli Institute for Particle Astrophysics and Cosmology, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA and , Stanford University, Stanford, California 94305, USA.
Abstract:
I present a new indirect search for dark matter (DM) using hydrogen-α (Hα) recombination emission. DM annihilation or decay products can ionize neutral gas; subsequent recombination cascades generate Hα photons through the 3→2 transition. In quiet gas-rich dwarf galaxies, the n=2 population is negligible, so Hα is effectively unabsorbed and traces the DM-energy injection site. Using the nondetection of extended Hα emission in the Leo T dwarf galaxy with Multi Unit Spectroscopic Explorer observations, I derive the first Hα-based limits on DM annihilation and decay, reaching leading sensitivity for parts of the eV-GeV mass range. Existing and upcoming telescopes can further extend this reach, establishing Hα imaging as a powerful DM search strategy.
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