Strongest constraints on dark acoustic oscillations from the Lyman-alpha forest

Abstract

We set the first constraints on a small-scale dark acoustic oscillation (DAO) in the linear matter power spectrum arising from dark sector interactions, with a full forward model of the Ly-$\alpha$ forest. No more than 30\% of dark matter can form DAOs if they peak at wavenumbers $<50h{\mathrm{Mpc}}^{-1}$ (95\% c.l.), probing scales $25\times$ smaller than the cosmic microwave background (CMB). Given the complex covariance of DAO and nuisance parameters, we use a deep kernel learning emulator of hydrodynamical simulations to capture imprints of linear oscillations in the Ly-$\alpha$ forest.

25 pages, 14 figures