Interstellar medium phases and abundances in the central parsec: A JWST MIRI/MRS view of the Galactic center

TL;DR

This study uses JWST MIRI/MRS observations and CLOUDY simulations to analyze the phases and chemical abundances of interstellar gas in the Galactic center's central parsec, revealing dominant warm ionized gas and recent star formation signatures.

Contribution

First comprehensive spectral analysis of the Galactic center's interstellar medium using JWST data combined with CLOUDY modeling to identify gas phases and chemical enrichment patterns.

Findings

Warm ionized gas dominates emission in both regions.

Molecular gas is significant in the CND but minimal in the CC.

Chemical abundances suggest recent enrichment by core-collapse supernovae.

Abstract

We used newly obtained observations from the Mid-Infrared Instrument (MIRI) equipped with the Medium Resolution Spectrometer (MRS) aboard the James Webb Space Telescope (JWST) to extract spectra covering the entire spectral range from 5 to 27~$\mu$m in the CND and in the CC. 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 $10^4$ and $10^{4.8}$~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 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.