Unveiling cosmological information on small scales with line intensity mapping

Abstract: One of the toughest challenges in modern cosmology is to probe the small scales $k \sim 0.5\,$Mpc$^{-1}$ in the matter power spectrum and clustering. We show that such small scales will be accessible via upcoming line-intensity mapping surveys, with carbon monoxide (CO) emission from star-forming galaxies at high redshifts as an example. While these galaxies cannot be individually detected and the two-point correlations of the intensity fluctuation maps is not accessible at these scales, the voxel intensity distribution (VID) of the highly non-Gaussian intensity maps is sensitive to the integrated emission from faint sources. As we describe, the main limitations are due to uncertainties related with the halo mass function and the CO emission model. We show that via the VID, high-redshift next-generation experiments can probe deviations from $\Lambda$CDM of order unity, while stage-3 experiments will be able to probe deviations as small as $\lesssim10\%$ at least up to $k\sim 10\,$Mpc$^{-1}$.