Mitigating Astrophysical Uncertainties in 21-cm Cosmology

The light of the first astrophysical objects is expected to leave an imprint on the global 21-cm signal as it heats, excites, and ionizes neutral hydrogen. This dependence on early astrophysics introduces significant uncertainties in modeling the 21-cm signal during Cosmic Dawn (CD). Here we show that a combination of observables including high-redshift UV luminosity functions, the cosmic X-ray background, the optical depth to reionization, and hydrogen absorption lines in quasar spectra, can be used to mitigate the astrophysical uncertainties assuming minimal modeling. Beyond its implications to standard astrophysics, we demonstrate how applying this procedure can improve sensitivity to new physics signatures in the global 21-cm signal. Taking the scenario of fractional millicharged dark matter (DM) as an example, we address astrophysical systematics to produce interesting predictions for upcoming experiments.