Density Profiles of CDM Microhalos and their Implications for Annihilation Boost Factors

Understand

In a standard cold dark matter (CDM) cosmology, microhalos at the CDM cutoff scale are the first and smallest objects expected to form in the universe.

• Here we present results of high resolution simulations of three representative roughly Earth-mass microhalos in order to determine their inner density profile.
• We find that CDM microhalos in simulations without a cutoff in the power spectrum roughly follow the NFW density profile, just like the much larger CDM halos on galaxy and galaxy cluster scales.
• But having a cutoff in the initial power spectrum at a typical neutralino free streaming scale of $10^{-7} M_{\odot}$ makes their inner density profiles considerably steeper, i.e.