Boosting Line Intensity Map Signal-to-Noise with the Ly-$\alpha$ Forest Cross-Correlation

Understand

We forecast the prospects for cross-correlating future line intensity mapping (LIM) surveys with the current and future Ly-$\alpha$ forest data.

• We use large cosmological hydrodynamic simulations to model the expected emission signal for the CO rotational transition in the COMAP LIM experiment at the 5-year benchmark and the Ly-$\alpha$ forest absorption signal for various surveys, including eBOSS, DESI, and PFS.
• We show that CO$\times$Ly-$\alpha$ forest can significantly enhance the detection signal-to-noise ratio of CO, with a $200$ to $300 \%$ improvement when cross-correlated with the forest observed in the Prime Focus Spectrograph (PFS) survey and a $50$ to $75\%$ enhancement for the currently available eBOSS or the upcoming DESI observations.
• We compare to the signal-to-noise improvements expected for a galaxy survey and show that CO$\times$Ly-$\alpha$ is competitive with even a spectroscopic galaxy survey in raw signal-to-noise.