Kavli Affiliate: Roberto Maiolino
| First 5 Authors: Yuki Isobe, Roberto Maiolino, Francesco D’Eugenio, Mirko Curti, Xihan Ji
| Summary:
The unexpectedly high nitrogen-to-oxygen (N/O) ratios observed in
high-redshift (z) galaxies have challenged our understanding of early star
formation. Notably, many of these nitrogen-rich galaxies show signatures of
active galactic nuclei (AGNs), suggesting a possible connection between black
hole formation and nitrogen enrichment. To explore this connection, we analyse
stacked spectra of z=4-7 broad-line and narrow-line AGNs using deep NIRSpec
data from the JADES survey. We identify a significant Niii] quintuplet and a
high electron density ($sim10^{4},mathrm{cm^{-3}}$) only in the broad-line
AGN stack, indicating nitrogen-rich ($log(mathrm{N/C})simeq0.5$,
$log(mathrm{N/O})>-0.6$) and dense gas similar to the high-z nitrogen-rich
galaxies. Our findings suggest that dense nuclear star formation may trap
nitrogen-rich gas in proto-globular clusters, in line with the high N/O
observed in local globular clusters; associated runaway stellar collisions
could produce intermediate-mass black hole seeds, as predicted by some models
and simulations, whose accretion results into AGN signatures. These findings
support scenarios connecting the early black hole seeding and growth to merging
processes within and between proto-globular clusters in primeval galaxies.
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