Modeling evolution of dark matter substructure and annihilation boost

Nagisa Hiroshima,Tomoaki Ishiyama,Shin’Ichiro Ando

doi:10.1088/1742-6596/1468/1/012050

Abstract

The structure of dark matter halo is hierarchical. Among them, small-scale structures in dark matter halo (so-called subhalos) can enhance dark matter annihilation signals. It is necessary to quantify boost factors by those subhalos to derive the property of dark matter with current/future gamma-ray observations. In order to derive the subhalo boost factors, calculations of halo structure covering more than 20 orders-of-magnitude in the halo mass up to a redshift of z ˜ 10 are required. This is beyond the capability of the current state-of-art cosmological N-body simulation which is a widely-adopted method to study the halo structure. In this talk, I introduce our analytical approach for the formalism of subhalo evolutions and the resultant boost factors. I show that the constraints on the annihilation cross-section obtained by isotropic γ-ray observations can be updated by several factors by taking the contribution from subhalos into account.

Highlights

There is strong evidence for the existence of dark matter, such as the distribution of matter in the Universe [1,2], rotation curves of galaxies [3,4], and bullet clusters [5]
Dark matter forms virialized objects—dark matter halos, which give some hints about its nature
IV, we show applications to the observational signatures such as the subhalo mass function and annihilation boost factor

Summary

Introduction

There is strong evidence for the existence of dark matter, such as the distribution of matter in the Universe [1,2], rotation curves of galaxies [3,4], and bullet clusters [5]. Dark matter forms virialized objects—dark matter halos, which give some hints about its nature. They encode information of scattering between dark matter particles and the standard model particles in the early Universe, through the minimum halo mass being predicted to be 10−12–10−3 M⊙ for the supersymmetric neutralino [8–11]. With given properties of the host and subhalos at their accretion, we can determine the tidal mass loss of the subhalos and remaining structures after some orbiting time. This procedure is studied through the analytical [12–14], semianalytical [15], and numerical [16–21] approaches

Results

Discussion

Conclusion