GA-NIFS: An extremely nitrogen-loud and chemically stratified galaxy at z∼ 5.55

2024/04/05 by Xihan Ji, Hannah Übler, Ji, Xihan +29 · 1 voice · 8 citations
Engineering · Physics and Astronomy · #Astronomical Observations and Instrumentation #Astronomy and Astrophysical Research #Real-time simulation and control systems #astro-ph.GA

paper · pdf · doi:10.48550/arxiv.2404.04148

openalex publication_date 2024/04/05 · openalex created_date 2024/04/09 · openalex updated_date 2026/07/30

Abstract

We report the chemical abundance pattern of GS_3073, a galaxy at z=5.55 which was previously confirmed to host an overmassive active black hole, by leveraging the detection of about 40 emission lines, combining JWST/NIRSpec observations and ground-based (VLT/VIMOS) data. Based on the rest-frame UV emission lines, which trace high-density (∼ 10⁵~\rm cm^-3) and highly ionized gas, we derived an abundance ratio of \rm log(N/O) = 0.42^+0.13_-0.10. At an estimated metallicity of 0.2~Z_\odot, this is the most extreme nitrogen-rich object found by JWST thus far. In comparison, the relative carbon abundance derived from the rest-frame UV emission lines is \rm log(C/O) = -0.38^+0.13_-0.11, which is not significantly higher than those in local galaxies and stars with similar metallicities. We also found potential detection of coronal lines including [FeVII]λ6087 and [FeXIV]λ5303, both blended with [CaV]. We inferred a range of Fe abundances compatible with those in local stars and galaxies. Overall, the chemical abundance pattern of GS_3073 is compatible with enrichment by super-massive stars with M_* \gtrsim 1000~M_\odot, asymptotic giant branch (AGB) stars, or Wolf-Rayet (WR) stars. Interestingly, when using optical emission lines which trace lower density (∼ 10³~\rm cm^-3) and lower ionization gas, we found a sub-solar N/O ratio. We interpret the difference in N/O derived from UV lines and optical lines as evidence for a stratified system, where the inner and denser region is both more chemically enriched and more ionized. Taking this luminous, well-studied system as a benchmark, our results suggest that nitrogen loudness in high-z galaxies is confined to the central, dense, and highly ionized region of the galaxies, while the bulk of the galaxies evolves more normally.

Cited by

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• The AURORA Survey: High-Redshift Empirical Metallicity Calibrations from Electron Temperature Measurements at z=2-10
• The AURORA Survey: Robust Helium Abundances at High Redshift Reveal A Subpopulation of Helium-Enhanced Galaxies in the Early Universe
• A Nitrogen-rich AGN Powering a Large Ionizing Bubble at z=8.63
• The JWST Spectroscopic Properties of Galaxies at z=9-14

Discussions

• GS_3073: a galaxy at z=5.55 which was previously confirmed to host an overmassive active black hole, and is now reported to have its chemical abundance analyzed. arxiv.org/abs/2404.04148 Images- jwstf [bsky, 16 points, 0 comments]

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