Minimum star-forming halo mass in axion cosmology

Abstract

Elucidating the particle physics nature of dark matter (DM) is one of the great challenges in modern science. The current lack of any direct DM detections in the laboratory heightens the need for astrophysical constraints, extending the search to DM models beyond the popular weakly interacting massive particle (WIMP) scenario. We here apply the classical Rees-Ostriker-Silk cooling criterion for galaxy formation to models with ultralight axion DM, also known as fuzzy dark matter (FDM). The resulting constraints provide a heuristic framework for upcoming observations, and our approximate analysis motivates the need for future, self-consistent simulations of FDM structure formation. We use observational constraints for the DM hosts of ultra faint dwarf (UFD) galaxies in the Local Group, together with the redshift constraints for the onset of primordial star formation from the recent EDGES 21-cm cosmology measurement, to illustrate this approach. We find that the existing constraints are straightforward to reconcile with standard $\Lambda$CDM, but disfavour FDM axion masses below $\sim 10^{-21}\mathrm{eV}/c^2$. The future potential for harnessing astrophysical probes of DM particle physics is compelling.

5 pages, 2 figures, MNRAS Letters: in press

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• Parkes Pulsar Timing Array constraints on ultralight scalar-field dark matter
• The Science of the Einstein Telescope
• The critical dark matter halo mass for Population III star formation: dependence on Lyman-Werner radiation, baryon-dark matter streaming velocity, and redshift
• Constraining First Star Formation with 21cm-Cosmology
• Effects of stellar-mass primordial black holes on first star formation
• BBN constraints on universally-coupled ultralight scalar dark matter
• Gravitational waves from mergers of Population III binary black holes: roles played by two evolution channels
• Probing the primordial Universe with 21-cm line from cosmic dawn/epoch of reionization
• Constraining the non-gravitational scattering of baryons and dark matter with early cosmic structure formation
• Probing Long-Range Forces Between Neutrinos with Cosmic Structures