Constraining Axion Dark Matter with Galactic-Centre Resonant Dynamics
Feb 12, 2025
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- 2502.08709 [astro-ph.CO]
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Abstract: (arXiv)
We study the influence of axion dark-matter cores on the orbits of stars at the Galactic centre. This dark matter candidate condenses into dense, solitonic cores, and, if a super-massive black hole is present at the centre of such a core, its central part forms a 'gravitational atom'. Here, we calculate the atom's contribution to the gravitational potential felt by a Galactic-centre star, for a generic quantum state of the atom. We study the angular-momentum dynamics this potential induces, and show that it is similar to vector resonant relaxation. Its influence is found to be sufficiently strong that such a dynamical component should be accounted for in Galactic-centre modelling. For the Milky Way, the atom is expected to have some spherical asymmetry, and we use this to derive a stability condition for the disc of young, massive stars at the Galactic centre - if the atom's mass is too large, then the disc would be destroyed. Thus, the existence of this disc constrains the mass of the axion particles comprising the solitonic core; for plausible parameter values, such a core is found to be in tension with the existence of the clockwise stellar disc at for . These constraints will tighten significantly with future, improved data.Note:
- Submitted, comments welcome
References(66)
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