Bounds on Velocity-Dependent Dark Matter-Baryon Scattering from Large-Scale Structure

We explore interacting dark matter (DM) models that allow DM and baryons to scatter off of each other with a cross section that scales with relative particle velocity. Using the effective field theory of large-scale structure, we perform the first analysis of BOSS full-shape galaxy clustering data for velocity-dependent DM-baryon interactions. We determine that while the addition of BOSS full-shape data visibly modifies the shape of the posterior distribution, it does not significantly alter the 95% confidence level intervals for the interaction cross section obtained from an analysis of the cosmic microwave (CMB) anisotropy from Planck measurements alone. Moreover, in agreement with previous findings, we note that the DM-baryon interacting model presents a good fit to both large-scale structure (LSS) data and CMB data and alleviates the $S_8$ tension between the two data sets. After combining LSS and CMB data with weak lensing data from the Dark Energy Survey, we find a $\gtrsim2\sigma$ preference for non-zero interactions between DM and baryons in a velocity-independent model. We also explore a scenario where only a fraction of DM undergoes scattering with baryons; we find a similar $\gtrsim2\sigma$ preference for the presence of interactions. Our results suggest that a suppression of the linear matter power spectrum at small scales may be needed to resolve certain discrepancies between LSS and CMB data that are found in the cold DM (CDM) scenario.