Metamorphosis of dwarf halo density profile under dark matter decays

TL;DR

This paper investigates how decaying dark matter affects dwarf galaxy density profiles, showing that decay leads to core flattening and better matches observed rotation curves, potentially solving small-scale CDM issues.

Contribution

The authors develop a new efficient algorithm and a simplified model to accurately simulate and analyze dwarf halo density profiles under dark matter decay effects.

Findings

Dark matter decay causes central density flattening in dwarf halos.

The simplified model agrees well with N-body simulation results.

DDM rotation curves match observations of local dwarf galaxies.

Abstract

We study the density profile of a dwarf halo in the decaying dark matter (DDM) cosmology, using a new algorithm that resolves halo density profiles down to the innermost $700$ pc robustly with high efficiency. Following Schwarzschild's orbit-based method, we have also developed a simplified model to calculate the DDM halo density profiles, which agree remarkably well with those from N-body simulations. Both zoom-in simulations and the simplified model reveal that dark matter decays lead to the flattening of central density and overall reduction of density in dwarf halos, and the underlying physics mechanisms are well illustrated by the simplified model. The slowly-rising scaled rotation curves of DDM dwarf halos agree with the observation of local dwarf galaxies. Our results suggest that the DDM holds great potential for resolving the small-scale problems faced by the cold dark matter (CDM) model.