Astronomy Tea Talk

The evolving cosmic abundance of cold molecular gas, along with its connection to the history of star formation, is an area of great interest in galaxy evolution. Advances in millimeter-wave instrumentation have resulted in exciting advances in this field through the study of CO emission lines, with ALMA, JVLA, and PdBI/NOEMA all conducting deep-fields surveys in search of high redshift CO emission during the past decade. However, studies conducted with these facilities are limited to relatively small areas of sky. Interpreting the results requires careful accounting for the effects of cosmic variance, and corrections for objects too uncommon to be found in the survey volume. I will present the result of our recent work attempting to quantify these uncertainties using mock observations of the IllustrisTNG simulation. I will then discuss CO line intensity mapping (LIM), an alternative survey approach that images large cosmological volumes at low sensitivity and extracts the aggregate CO signal from intensity fluctuations captured by the power spectrum of the map. LIM enables surveys over much larger volumes and can recover information about galaxies fainter than the threshold for direct detection, making it an excellent complement to previous projects. I will present our groups recent constraints on the CO-galaxy cross-power spectrum, which have served as a proof of concept for LIM studies and already demonstrate their power to constrain cosmic molecular gas abundances. Finally, I will provide an overview of a project to constrain the luminosity ratios of the CO(1-0), CO(2-1) and CO(3-2) lines, which are necessary for interpreting results of both conventional and LIM surveys.