Hints of dark matter-neutrino interactions in Lyman-$α$ data

Abstract: In this work we investigate the possibility that dark matter and (massive) neutrinos can interact via a simple, constant cross section. Building on previous numerical efforts, we constrain this model with CMB, BAO and, in particular, Lyman-$\alpha$ data. We find that the latter hint to a significant departure from $\Lambda$CDM, with a preference for an interaction strength about 3$\sigma$ away from zero. We trace the origin of this preference back to the additional tilt that the interacting scenario can imprint on the Lyman-$\alpha$ flux power spectrum, solving a well-known tension in the determination of this quantity between early-time and Lyman-$\alpha$ probes. Future work including complementary Lyman-$\alpha$ data as well as dedicated numerical simulations will be crucial in order to test these results.