A new paper by Harley Katz and SPHINX collaborators is out, titled “The Nature of High [OIII]88𝜇m/[CII]158𝜇m Galaxies in the Epoch of Reionization: Low Carbon Abundance and a Top-Heavy IMF?”. The paper addresses the high [OIII] to [CII] metal-line ratios observed in extreme-redshift galaxies and uses mock-observations of SPHINX simulation galaxies to gain insight, finding that SPHINX galaxies reproduce these observed high ratios only if high-ratios of C/O abundances are assumed. This in turn implies that stellar populations in the early Universe may have been significantly more top-heavy than in the present-day, in other words that stars were generally more massive at early times.
