Contributions of dark matter annihilation within ultracompact minihalos to the 21cm background signal

TL;DR

This paper investigates how dark matter annihilation within ultracompact minihalos influences the 21cm background signal during the universe's dark age, highlighting a potential new probe of dark matter structures.

Contribution

It introduces the role of ultracompact dark matter minihalos in affecting the 21cm signal through dark matter annihilation, a novel aspect not previously explored.

Findings

Dark matter annihilation in UCMHs impacts the 21cm background signal.

UCMHs' steep density profile enhances annihilation effects.

Earlier formation time of UCMHs makes their contribution significant.

Abstract

In the dark age of the universe, any exotic sources, e.g. the dark matter annihilation, which inject the energy into the intergalactic medium (IGM) will left some imprint on the 21cm background signal. Recently, one new kind of dark matter structure named ultracompact dark matter minihalo (UCMHs) was proposed. Near the inner part UCMHs, the distribution of dark matter particles are steeper than that of the general dark matter halos, $\rho_{\rm UCMHs}(r) \sim r^{-2.25}$, and the formation time of UCMHs is earlier, $z_c \sim 1000$. Therefore, it is excepted that the dark matter annihilation within UCMHs can effect the 21cm background signal. In this paper, we investigated the contributions of the dark matter annihilation within UCMHs to the 21cm background signal.