Title: Constraining Dark Matter Annihilation in Early Matter Dominated Era Cosmologies Using the Global 21 cm Absorption Signal
Although standard cosmology assumes that relativistic particles dominate the energy density of the Universe quickly after inflation, a variety of well-motivated scenarios predict an early matter dominated era (EMDE) before the onset of the radiation dominated era (RDE). Subhorizon dark matter (DM) density perturbations grow faster during an EMDE than during an RDE, leading to an increased abundance of microhalos that form far earlier than in standard models of structure formation. This enhancement of small-scale structure boosts the DM annihilation rate, and we discuss how to compute boost factors for cosmologies with EMDEs. These boost factors can be several orders of magnitude greater than in standard cosmology, and the additional energy injected from annihilating DM increases the temperature of the intergalactic medium. During the Dark Ages the sky-averaged (global) 21 cm signal is highly sensitive to the IGM temperature, and we use predictions of the global 21 cm signal to forecast bounds on the DM annihilation cross section in cosmologies with EMDEs.
Meeting ID: 978 8521 4243