Ultra-light axions (ULAs) are a promising and intriguing set of dark-matter candidates. We study the prospects to use forthcoming measurements of 21-cm fluctuations from cosmic dawn to probe ULAs. In this poster, I focus in particular on the velocity acoustic oscillations (VAOs) in the large-scale 21-cm power spectrum, features imprinted by the long-wavelength (k∼0.1 1/Mpc) modulation, by dark-matter--baryon relative velocities, of the small-scale (k∼10−1000 1/Mpc) power required to produce the stars that heat the neutral hydrogen. Damping of small-scale power by ULAs reduces the star-formation rate at cosmic dawn which then leads to a reduced VAO amplitude. Accounting for different assumptions for feedback and foregrounds, I will show that the 21-cm experiments may be sensitive to ULAs with masses up to 10−18eV, two decades of mass higher than current constraints.
|In-person or Virtual?||In-person|