Speaker
Description
The 21-cm signal provides a new window into the thermal and ionization history of the early Universe, making it a powerful probe of exotic energy injection processes, including those sourced by dark matter (DM). We develop an effective parametric model for the heating deposition function, $f_{heat}(z)$, capturing the redshift-dependent impact of generic energy injection histories on the intergalactic medium (IGM). This flexible parameterization enables fast and accurate predictions of the 21-cm signal under diverse astrophysical conditions.
Combined with a Simulation-Based Inference (SBI) framework, this approach enables efficient exploration of the connection between energy injection and 21-cm observables without relying on computationally expensive particle-level simulations. We show that the 21-cm power spectrum is primarily sensitive to the overall heating amplitude, allowing robust and largely model-independent constraints across a broad class of exotic energy injection scenarios relevant to upcoming experiments such as SKA.
As a concrete application, we focus on DM decay into $e^{-}e^{+}$ pairs and calibrate our model prior against detailed particle-physics calculations from the DarkHistory code. We find that the evolution of $f_{heat}(z)$ exhibits partial recovery in an optimal heating regime, where DM-driven heating dominates over astrophysical contributions.
Our results establish a scalable framework for constraining exotic energy injection using the 21-cm power spectrum, and provide a foundation for forecasting the sensitivity of next-generation experiments to a wide range of beyond-standard-model heating histories.