JWST Detects Deuterated Aliphatic Features in 30 Doradus UIE Bands

The arXiv preprint reports spatially resolved observations across 30 Doradus using JWST's NIRSpec and MIRI instruments. These data show the 3.4 micron aliphatic C-H stretch, the 6.85 micron deformation mode with previously unreported substructure at 6.83, 6.86 and 6.88 microns, and the 4.65 micron C-D stretch. The detection occurs in an environment with roughly half-solar metallicity, providing a direct link between laboratory deuteration experiments and extragalactic infrared emission carriers.

This finding extends deuterium fractionation studies from the Milky Way to low-metallicity star-forming regions. Aliphatic deuteration implies that the unidentified infrared emission carriers incorporate both aromatic rings and aliphatic chains formed under conditions that preserve D/H enhancements. Such chemistry could seed organic precursors available during planet formation in metal-poor disks, altering assumptions about the initial inventory of complex molecules delivered to forming planets.

Prior ground-based and Spitzer observations lacked the sensitivity and spectral resolution to isolate these weak deuterated features. The new substructure at 6.85 microns suggests multiple distinct aliphatic environments or matrix effects not captured in current PAH models. Follow-up mapping of additional LMC and SMC regions with JWST will test whether the aliphatic deuteration fraction scales with local radiation field or metallicity.