Isotopic ratios as probes of star formation and the origin of molecular gas in the Central Molecular Zone
Isotopic ratios are used to study physical conditions and nucleosynthetic history in the Central Molecular Zone (CMZ). Deuterium fractionation shows a cold, quiescent gas component exists despite warm turbulence. New carbon isotopic measurements suggest this gas has undergone different chemical evolution than previously assumed, supporting an inflow scenario from the inner Galactic disk.