2023/07/03 by Yuki Isobe, Isobe, Yuki, Masami Ouchi +21 · 6 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #Stellar, planetary, and galactic studies
paper · pdf · doi:10.48550/arxiv.2307.00710
openalex publication_date 2023/07/03 · openalex created_date 2023/07/05 · openalex updated_date 2026/07/28
We present chemical abundance ratios of 70 star-forming galaxies at z∼4-10 observed by the JWST/NIRSpec ERO, GLASS, and CEERS programs. Among the 70 galaxies, we have pinpointed 2 galaxies, CEERS01019 at z=8.68 and GLASS150008 at z=6.23, with extremely low C/N ([C/N]\lesssim -1), evidenced with CIII]λλ1907,1909, NIII]λ1750, and NIV]λλ1483,1486, which show high N/O ratios ([N/O]\gtrsim 0.5) comparable with the one of GN-z11 regardless of whether stellar or AGN radiation is assumed. Such low C/N and high N/O ratios found in CEERS01019 and GLASS150008 (additionally identified in GN-z11) are largely biased towards the equilibrium of the CNO cycle, suggesting that these 3 galaxies are enriched by metals processed by the CNO cycle. On the C/N vs. O/H plane, these 3 galaxies do not coincide with Galactic HII regions, normal star-forming galaxies, and nitrogen-loud quasars with asymptotic giant branch stars, but globular-cluster (GC) stars, indicating a connection with GC formation. We compare C/O and N/O of these 3 galaxies with those of theoretical models, and find that these 3 galaxies are explained by scenarios with dominant CNO-cycle materials, i.e. Wolf-Rayet stars, supermassive (103-105 M\odot) stars, and tidal disruption events, interestingly with a requirement of frequent direct collapses. For all the 70 galaxies, we present measurements of Ne/O, S/O, and Ar/O, together with C/O and N/O. We identify 4 galaxies with very low Ne/O, log(\rm Ne/O)<-1.0, indicating abundant massive (\gtrsim30 M_\odot) stars.