JWST Observations Reveal High Helium Emission in Early Galaxies

Recent observations from the James Webb Space Telescope (JWST) have identified strong helium (He I) emission lines in three high-redshift galaxies at approximately redshift z ~ 6. The study, conducted by Hiroto Yanagisawa and a team of 16 co-authors, presents findings that suggest these galaxies exhibit significantly higher He/H abundance ratios compared to local dwarf galaxies. The galaxies observed include GS-NDG-9422, RXCJ2248-ID, and GLASS150008, with spectroscopic coverage extending from He I λ4471 and He II λ4686 to He I λ7065.

The researchers found that the He I/Hβ flux ratios in these high-redshift galaxies are generally larger than those observed in local dwarf galaxies. The analysis indicates that the high-redshift galaxies show helium overabundance with He/H ratios greater than 0.10 or high electron densities around 10³ to 10⁴ cm⁻³, which are significantly larger than local values. In contrast, local dwarf galaxies displayed lower He/H and electron density values.

The study explores two potential scenarios to explain these findings: one suggests that the overabundant helium and nitrogen in these galaxies cannot be solely attributed to the standard chemical enrichment processes from core-collapse supernovae, while the other indicates that the strong helium lines may originate from dense central clouds within the high-redshift galaxies due to excessive collisional excitation.

This research contributes to our understanding of the chemical evolution of galaxies in the early universe and poses questions about the processes that govern star formation and chemical enrichment in these distant galaxies. The full findings are detailed in the paper titled "Strong He I Emission Lines in High N/O Galaxies at z ~ 6 Identified in JWST Spectra: High He/H Abundance Ratios or High Electron Densities?" available on arXiv.