Semianalytic model for decaying dark matter halos

TL;DR

This paper presents a new semianalytic model for decaying dark matter that predicts its effects on halo structure and subhalo populations, aligning well with simulation results and aiding future observational constraints.

Contribution

The authors introduce a semianalytic model for DDM effects on halos, implemented in Galacticus, capturing heating, mass loss, and subhalo suppression, enabling efficient exploration of DDM parameter space.

Findings

DDM flattens and reduces halo inner density profiles.

DDM causes a mass-dependent suppression of subhalo populations.

Model predictions align with N-body simulation results.

Abstract

Decaying dark matter (DDM) affects the evolution of cosmic structure relative to standard cold, collisionless, stable dark matter (CDM). We introduce a new semianalytic model for the effects of two-body DDM on halo structure and subhalo populations. In this scenario, cold parent dark matter particles decay into less massive daughter particles plus dark radiation with a lifetime comparable to the age of the Universe. Our DDM model is implemented in the open-source software $\texttt{Galacticus}$ and accounts for heating (due to the velocity kicks imparted on daughter particles) and mass loss (due to the parent-daughter mass splitting). We show that decays flatten and reduce the amplitude of halos' inner density profiles. These effects make DDM subhalos susceptible to tidal disruption, which we show yields a mass-dependent suppression of the subhalo mass function relative to CDM. Our predictions for DDM density profiles, velocity dispersion profiles, and subhalo populations are consistent with results from isolated and cosmological DDM N-body simulations. Thus, our model enables efficient and accurate exploration of DDM parameter space and will be useful for deriving constraints from upcoming small-scale structure observations.