GA-NIFS: an extremely nitrogen-loud and chemically stratified galaxy at z ~ 5.55
Year: 2024
Type: article
Abstract: ABSTRACT We report the chemical abundance pattern of GS_3073, a galaxy hosting an overmassive active black hole at $z=5.55$, by leveraging observations from JWST/NIRSpec and Very Large Telescope/VIsible Multi-Object Spectrograph. Based on the rest-frame ultraviolet (UV) emission lines, which trace high-density ($\sim 10^5~{\rm cm^{-3}}$) and highly ionized gas, we derive $\rm \log (N/O) = 0.42^{+0.13}_{-0.10}$. 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 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 [Fe vii]$\lambda 6087$ and [Fe xiv]$\lambda 5303$, both blended with [Ca v]. 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 supermassive stars with $M_* \gtrsim 1000~M_\odot$, asymptotic giant branch stars, or Wolf–Rayet stars. Interestingly, when using optical emission lines that trace lower density ($\sim 10^3~{\rm cm}^{-3}$) and lower ionization gas, we found a sub-solar N/O ratio, consistent with local galaxies at the same metallicity. 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. Our results suggest that nitrogen loudness in high-z galaxies might be confined to the central, dense, and highly ionized regions of the galaxies, while the bulk of the galaxies evolves more normally.
Institutions: University of Cambridge, University College London, Centro de Astrobiología, University of Oxford, Centre National de la Recherche Scientifique, Institut d'Astrophysique de Paris, Sorbonne Université, Space Telescope Science Institute, European Space Agency, Arcetri Astrophysical Observatory, European Southern Observatory
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,012
Funders: National Aeronautics and Space Administration, Kavli Foundation, Albert Ellis Institute, George Mason University, UK Research and Innovation, Royal Society, European Commission, Isaac Newton Trust, Ministerio de Ciencia e Innovación, Istituto Nazionale di Astrofisica, Goddard Space Flight Center, Science and Technology Facilities Council, Agencia Estatal de Investigación, H2020 European Research Council
Awards: G1175115578, G1461837398, Support of the astronomical research of the Cavendish Astrophysics Group, G1577046871, G1855990336, G2005369488, G2144673021, G2262748287, G2309174360, G2601397997, G2660406951, Finding the most distant galaxies with NIRSpec guaranteed time on the James Webb Space Telescope, G300979063, G3224170850, G3228396264, G3275705967, G3326551379, G3452655474, G3480869486, G3518538256, G3681454997, Support of the Astronomical Research of the Cavendish Astrophysics Group, G4042783231, G4161023950, G425668148, G430777504, G434337789, G480866104, G4915654406, G5080475149, G5195188938, G531848386, G5368796297, G5403136496, G5421974903, G5480708011, G5842359595, G6116079057, G6282605728, G7001747737, G7084143925, G7434936867, G7678768968, G7736885172, G7935691682, G8318265897, G8631195605, G871455044, G8920660035, G8931419319, G99296377
OpenAlex ID: W4403501276