Abstract

Contributed Talk - Splinter ALMA2040

Beyond 12CO: Current and Future Prospects for Probing Extragalactic Molecular Gas with ALMA

Jakob den Brok
MPIA

The PHANGS-ALMA Large Program has reshaped our understanding of the intricate relationship between molecular gas and star formation across various environments within nearby galaxies. While the bright 12CO(2–1) line remains a cornerstone tracer of molecular gas in extragalactic giant molecular clouds, its optical thickness limits our ability to infer key physical conditions. In contrast, the fainter 13CO and C18O lines are typically optically thin and offer a more direct view of gas temperature, density, and opacity. Building on den Brok et al. (2023b, 2025a, 2025b) and leveraging data from ALMA, IRAM 30m/NOEMA, and the SMA, I will showcase our current ability to characterize the molecular gas in distinct environments across star-forming galaxies. CO isotopologues open a powerful new window into the molecular ISM diagnostics, with critical implications for star formation models and the interpretation of high-redshift CO observations. I will conclude by outlining how a transformative ALMA upgrade, including multi-band capabilities, and more sensitivity at larger baselines, could enable instantaneous, high-resolution mapping of gas conditions across entire galaxies, unlocking a new era of systematic, spatially resolved studies of the star-forming reservoir.