Submitted by S. Brereton on Wed, 28/05/2025 - 07:24
Kavli Fellow James Alvey and collaborators have recently found new methods to put a fundamental limit on the mass of dark matter. A widely used argument suggests that the de Broglie wavelength of dark matter particles must be smaller than the size of the galaxies they inhabit. This requirement has typically implied that the mass of dark matter particles should be greater than around 10⁻²² electronvolts (eV), taking into account the observation of dwarf galaxies. However, this estimate has lacked a rigorous, data-driven foundation. In the new study, which appeared on the cover of Physical Review Letters in April, the authors used stellar kinematic data from the Milky Way satellite galaxy Leo II to construct a statistically consistent picture of how dark matter is distributed in such systems. Comparing this to a flexible, model-independent reconstruction of the galaxy’s density profile via solutions to the Schrödinger equation, and using a novel statistical measure, the team establish that a consistent description of dark matter in Leo II requires the particle mass to actually exceed 2.2 × 10⁻²¹ eV. Importantly, this new lower limit does not rely on any assumptions about cosmology, the particle’s spin, or how dark matter behaves dynamically. It simply assumes that dark matter is predominantly made up of a single type of bosonic particle and therefore provides a key benchmark for the range of possible dark matter models.
The full paper is available via Open Access at this link.
