On estimating the cosmic molecular gas density from CO Line Intensity Mapping observations

Understand

The Millimeter-wave Intensity Mapping Experiment (mmIME) recently reported a detection of excess spatial fluctuations at a wavelength of 3 mm, which can be attributed to unresolved emission of several CO rotational transitions between $z\sim1-5$.

• We study the implications of this data for the high-redshift interstellar medium using a suite of state-of-the-art semianalytic simulations which have successfully reproduced many other sub-millimeter line observations across the relevant redshift range.
• We find that the semianalytic predictions are mildly in tension with the mmIME result, with a predicted CO power $\sim3.5\sigma$ below what was observed.
• We explore some simple modifications to the models which could resolve this tension.