Constraining the expansion history and early dark energy with line intensity mapping

We consider the potential for line intensity mapping (IM) experiments to measure the baryon acoustic oscillations (BAO) from $3<z<6$. This would constrain the expansion history in a redshift range that is currently unexplored. We calculate the map depths that future IM experiments targeting the CO(1-0) rotational transition line and [CII] ionized carbon fine-structure line would need to achieve in order to measure the BAO. We find that near-future IM experiments could constrain the BAO scale to 5% or better depending on CO/[CII] model amplitude. This measurement is at a precision that could make competitive constraints on models of early dark energy.