Probing Dark Matter–Baryon Interactions Using Line Intensity Mapping: Forecasts for COMAP-EoR and COMAP-ERA

We investigate the potential of line-intensity mapping (LIM) as a novel probe of dark matter–baryon (DM-b) interactions using upcoming CO surveys from COMAP-EoR and COMAP-ERA. In scenarios where dark matter elastically scatters with baryons, the exchange of momentum and heat suppresses the growth of structure, leading to characteristic signatures in the linear matter power spectrum (Pm) and halo mass function (HMF). These effects propagate to LIM observables, including the power spectrum (PS) and the voxel intensity distribution (VID). We perform Fisher forecasts to constrain the DM-b scattering cross section for a range of velocity-dependent interactions using both statistics individually and their joint (PS+VID) analysis. We find that LIM observables can place competitive constraints on DM-b interactions across a wide mass range. The VID significantly outperforms the PS in constraining astrophysical parameters and helps break degeneracies between cosmology and astrophysics. A joint analysis further improves sensitivity, demonstrating the power of combining Gaussian (PS) and non-Gaussian (VID) information. Overall, our results establish LIM as a promising and complementary probe of dark matter microphysics, with the potential to access parameter space beyond current cosmological and astrophysical constraints.