Abstract We present Local Thermodynamic Equilibrium (LTE) estimates of the physical properties and star formation efficiency (SFE) of molecular gas in the Central Molecular Zone (CMZ), using new 12CO J = 2 → 1 observations from the James Clerk Maxwell Telescope. Combined with CHIMPS2 12CO and 13CO J = 3 → 2, and SEDIGISM 13CO J = 2 → 1 data, we estimate a median excitation temperature of Tex = 11 K for 13CO throughout the CMZ, with peaks exceeding 120 K in the Sgr B1/B2 complex. Cooler gas dominates around Sgr A and nearby clouds. We derive a median H2 column-density of N (H2) = 2 × 1022 cm−2 and a total 13CO-traced gas mass of Mgas = 7 × 106 M⊙, consistent with previous estimates when accounting for spatial coverage. The instantaneous SFE is assessed using Hi-GAL compact sources detected at 70- m and 160–500- m. The 70- m-bright SFE, tracing current star formation, is modest overall but elevated in Sgr B1/B2, the Arches cluster, and Sgr C. In contrast, the 160–500- m SFE, tracing cold pre-stellar gas, is more broadly enhanced, particularly in the dust ridge clouds and towards negative longitudes surrounding Sgr C. The contrasting distributions suggest an evolutionary gradient in SFE, consistent with a transition from dense, cold gas to embedded protostars. Our results imply that the CMZ may be enter a more active phase of star formation, with large reservoirs of gas primed for future activity.
King et al. (Fri,) studied this question.