Abstract
In the next few years, observations of the 21-cm signal will open a window to the cosmic dawn epoch, when the first stars formed. It is conventional to interpret these observations through semi-numerical or hydrodynamical simulations, which are often computationally intensive and inflexible to exotic cosmological or astrophysical effects. I will present a new approach to predict the 21-cm global signal and fluctuations in the presence of PopIII stars in seconds. PopIII stars, residing in low-mass molecular-cooling halos, are highly sensitive to feedback, especially from H2-dissociating Lyman-Werner radiation and dark matter-baryon relative velocities. To bypass expensive numerical simulations, we develop an effective prescription of the star formation rate density in the presence of PopIII stars. Our method recovers the full nonlinear distributions of radiative fields that determine the 21-cm signal including anisotropic feedback. I will show how PopIII stars impact the 21-cm global signal and power spectrum across cosmic time and at different distance scales. I will also highlight how the spatial modulation of the relative velocities induces Velocity Acoustic Oscillations in 21-cm power spectra, providing us with a new and robust cosmological standard ruler. Our public code, Zeus21, can predict 21-cm observables in seconds, presenting a meaningful first step towards rapid precision astrophysics and cosmology in the first billion years.
