James Webb Space Telescope Feed Post

Harvard ADS: First direct carbon abundance measured at z>10 in the lensed galaxy MACS0647-JD

Paper abstract: Investigating the metal enrichment in the early universe helps us constrain theories about the first stars and study the ages of galaxies. The lensed galaxy MACS0647-JD at z=10.17 is the brightest galaxy known at z > 10. Previous work analyzing JWST NIRSpec and MIRI data yielded a direct metallicity \rm{12+log(O/H)}=7.79\pm0.09 (~ 0.13 Z_\odot) and electron density \rm{log}(n_e / \rm{cm^{-3}}) = 2.9 \pm 0.5, the most distant such measurements to date. Here we estimate the direct C/O abundance for the first time at z > 10, finding a sub-solar {\rm log(C/O)}=-0.44^{+0.06}_{-0.07}. This is higher than other z>6 galaxies with direct C/O measurements, likely due to higher metallicity. It is also slightly higher than galaxies in the local universe with similar metallicity. This may suggest a very efficient and rapid burst of star formation, a low effective oxygen abundance yield, or the presence of unusual stellar populations including supermassive stars. Alternatively, the strong CIII]{\rm {\lambda}{\lambda}}1907,1909 emission (14\pm 3\,{\r{A}} rest-frame EW) may originate from just one of the two component star clusters JDB (r ~ 20 pc). Future NIRSpec IFU spectroscopic observations of MACS0647-JD will be promising for disentangling C/O in the two components to constrain the chemistry of individual star clusters just 460 Myr after the Big Bang.