Kavli Affiliate: Roberto Maiolino
| First 5 Authors: Tiger Yu-Yang Hsiao, Michael W. Topping, Dan Coe, John Chisholm, Danielle A. Berg
| Summary:
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
$rm{12+log(O/H)}=7.79pm0.09$ ($sim$ 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
($14pm 3,{r{A}}$ rest-frame EW) may originate from just one of the two
component star clusters JDB ($r sim 20$ 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.
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