Kavli Affiliate: Risa Wechsler
| Summary:
We generalize lower limits on the dark matter (DM) particle mass $m$ derived from Milky Way (MW) satellite galaxy abundances to scenarios in which DM is an ultralight scalar field produced with a field power spectrum peaked at a subhorizon wavenumber $k_*$. In these models, the DM field free-streams similar to warm dark matter while also exhibiting significant small-scale wave interference effects. The resulting dimensionless density power spectrum shows two effects: (i) free-streaming suppression at $k_rm fssim k_rm eq/[(k_*/a_rm eqm)ln(a_rm eqm/k_*)]$; (ii) Poisson-like enhancement related to wave interference, at $kgtrsim10^-2k_*$, which saturates near the Jeans scale $k_rm Jsim k_rm eq/(k_*/a_rm eqm)$. Comparing these predictions with established constraints on a free-streaming cutoff in the linear matter power spectrum from the MW satellite population, we obtain $m>6times10^-18,rm eV,(k_*/10^4,rm Mpc^-1)$ for $k_*>10^4,rm Mpc^-1$ at 95% confidence. For smaller $k_*$, Poisson-noise enhancement on MW satellite scales weakens the constraint, yielding $m>6times10^-18,rm eV,(k_*/10^4,rm Mpc^-1)^2$ for $k_*<10^4,rm Mpc^-1$ at 95% confidence.
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