ISM phases and abundances in the central parsec

We used the photoionization code CLOUDY to generate synthetic spectra with the same spectral range and resolution, simulating a wide range of gas phases and abundances. We then determined the contribution of each phase to the spectra. Once the abundances and contribution from each phase of the gas were determined, we identified four dominant phases and performed a spatial analysis to determine their contribution to each spaxel of the datacubes.

We find that in both the CND and the CC, the bulk of the emission originates from warm ionized gas with temperatures of between 104 and 104.8 K. In the CND, molecular gas contributes significantly to the flux and is spatially structured, while the CC shows minimal molecular gas content, as is expected from these regions. Coronal gas is detected in both regions at the interface between molecular and warm ionized gas. The hottest coronal phase appears faint and patchy in the CC, and has an elongated morphology in the CND.

Abundance fitting (in solar-normalized logarithmic units) is primarily constrained by abundances: we measure a robust depletion of Fe relative to alpha elements with log(Fe/alpha)=-0.78+/-0.20 (CC) and -0.84+/-0.26 (CND), while CNO is only mildly enhanced relative to alpha, log(CNO/alpha)=0.27+/-0.20 (CC) and 0.05+/-0.26 (CND). Absolute abundances are supersolar but more degenerate; the best-fitting models yield (log alpha, log CNO, log Fe) = (1.4, 1.4, 0.4) in the CC and (2.0, 1.8, 1.2) in the CND.

The observed abundance pattern (enhanced CNO and alpha elements with suppressed Fe) indicates a chemically young environment, recently enriched by core-collapse supernovae and stellar winds, with a limited contribution from older Type Ia supernovae. This favors a scenario of massive, recent star formation rather than cumulative long-term enrichment. Additionally, the projected orientation of the newly identified CND elongated hot coronal feature, perpendicular to the direction toward the SMBH, suggests the action of a large-scale shock possibly resulting from past energetic outflows.