Massive prompt cusps: A new signature of warm dark matter

Abstract

Every dark matter halo and subhalo is expected to have a prompt $\rho \propto r^{-1.5}$ central density cusp, which is a relic of its condensation out of the smooth mass distribution of the early universe. The sizes of these prompt cusps are linked to the scales of the peaks in the initial density field from which they formed. In warm dark matter (WDM) models, the smoothing scale set by free streaming of the dark matter can result in prompt cusps with masses of order $10^7$ M${}_{\odot }$. We show that WDM models with particle masses ranging from 2 to 6 keV predict prompt cusps that could detectably alter the observed kinematics of Local Group dwarf galaxies. Thus, prompt cusps present a viable new probe of WDM. A prompt cusp's properties are highly sensitive to when it formed, so prospects can be improved with a better understanding of when the haloes of the Local Group dwarfs originally formed. Tidal stripping can also affect prompt cusps, so constraints on satellite galaxy orbits can further tighten WDM inferences.

5 pages, 6 figures; accepted by MNRAS Letters. Includes more detail on the sampling of prompt cusps

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Cited by in corpus (8)

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• Signatures of dark and baryonic structures on weakly lensed gravitational waves
• Limits on dark matter annihilation in prompt cusps from the isotropic gamma-ray background
• Can prompt cusps of WIMP dark matter be detected as individual gamma-ray sources?
• Measurement of Substructure from the Kinematics of the GD-1 Stellar Stream
• The cusp-halo relation
• Structure Formation with Warm White Noise: Effects of Finite Number Density and Velocity Dispersion in Particle and Wave Dark Matter
• Role of prompt cusps in driving the core collapse of SIDM halos