Kavli Affiliate: Andrey Kravtsov
| First 5 Authors: Xihan Ji, Vasily Belokurov, Roberto Maiolino, Stephanie Monty, Yuki Isobe
| Summary:
Recent JWST observations have revealed a growing population of galaxies at
$z>4$ with elevated nitrogen-to-oxygen ratios. These "N/O-enhanced" galaxies
(NOEGs) exhibit near- to super-solar N/O at sub-solar O/H, clearly deviating
from the well-established scaling relation between N/O and O/H observed in
local galaxies. The origin of this abundance anomaly is unclear. Interestingly,
local globular clusters also exhibit anomalous light-element abundances, whose
origin remains debated. In this work, we compare the chemical abundance
patterns of 22 known NOEGs at $0lesssim zlesssim 12$ — primarily discovered
with JWST — to those observed in local globular clusters. We find striking
similarities in the abundances of C, N, O, Fe, and He between the two
populations. The similar abundance patterns support the scenario in which
globular cluster stars formed within proto-cluster environments — similar to
those traced by NOEGs — that were self-enriched. Indeed, the enhancement in
N/O in early galaxies appears to be only found in dense stellar environments
with $Sigma _{star}gtrsim 10^{2.5}~M_odot~{rm pc^{-2}}$, as expected for
the progenitors of globular clusters in the Milky Way, and similar to those of
star clusters identified in strongly lensed high-redshift galaxies.
Furthermore, we find a tentative positive correlation between N/O ratios and
stellar mass among NOEGs. The apparent high occurrence rate of NOEGs at high
redshift is consistent with the picture of cluster-dominated star formation
during the early stages of galaxy evolution. Measuring chemical abundances
across diverse stellar environments in high-redshift galaxies will be crucial
for elucidating the connection between NOEGs and globular clusters.
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