Evidence of extreme ionization conditions and low metallicity in GHZ2/GLASS-z12 from a combined analysis of NIRSpec and MIRI observations
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2024
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| author | Calabro, Antonello Castellano, Marco Zavala, Jorge A. Pentericci, Laura Haro, Pablo Arrabal Bakx, Tom J. L. C. Burgarella, Denis Casey, Caitlin M. Dickinson, Mark Finkelstein, Steven L. Fontana, Adriano Llerena, Mario Mascia, Sara Merlin, Emiliano Mitsuhashi, Ikki Napolitano, Lorenzo Paris, Diego Perez-Gonzalez, Pablo G. Roberts-Borsani, Guido Santini, Paola Treu, Tommaso Vanzella, Eros |
| author_facet | Calabro, Antonello Castellano, Marco Zavala, Jorge A. Pentericci, Laura Haro, Pablo Arrabal Bakx, Tom J. L. C. Burgarella, Denis Casey, Caitlin M. Dickinson, Mark Finkelstein, Steven L. Fontana, Adriano Llerena, Mario Mascia, Sara Merlin, Emiliano Mitsuhashi, Ikki Napolitano, Lorenzo Paris, Diego Perez-Gonzalez, Pablo G. Roberts-Borsani, Guido Santini, Paola Treu, Tommaso Vanzella, Eros |
| contents | GHZ2/GLASS-z12 has been recently observed by JWST with both NIRSpec and MIRI spectrographs, making it the most distant galaxy ($z_{spec}=12.34$) with complete spectroscopic coverage from rest-frame UV to optical. It is identified as a strong CIV$_{1549}$ emitter with many detected emission lines (NIV], HeII, OIII], NIII], CIII], [OII], [NeIII], [OIII], and H$α$), including a remarkable OIII$_{1333}$ Bowen fluorescence line. We analyze in this paper the joint NIRSpec+MIRI spectral data set. Combining six optical diagnostics (R2, R3, R23, O32, Ne3O2, and Ne3O2Hd), we find extreme ionization conditions, with O32 $=1.39 \pm 0.19$ and Ne3O2 $=0.37 \pm 0.18$ in stark excess compared to typical values in the ISM at lower redshifts. These line properties are compatible either with an AGN or with a compact, dense star-forming environment ($Σ_{\rm SFR}$ $\sim 10^2$-$10^3$ Msun/yr/kpc$^2$), with a high ionization parameter ($\log_{10}$(U) $=-1.75 \pm 0.16$), a high ionizing photon production efficiency $\log(ξ_{\rm ion}) = 25.7_{-0.1}^{+0.2}$, and a low, although not pristine, metal content between $5\%$ and $11\%$ Z$_\odot$ (confirmed by the T$_e$ method), indicating a rapid metal enrichment in the last few Myrs. These properties also suggest that a substantial amount of ionizing photons ($\sim 10\%$) are leaking outside. The general lessons learned from GHZ2 are the following: (i) the UV to optical combined nebular indicators are broadly in agreement with UV-only or optical-only indicators. (ii) UV+optical diagnostics fail to discriminate between an AGN and star-formation in a low metallicity, high density, and extreme ionization environment. (iii) comparing the nebular line ratios with local analogs may be approaching its limits at $z \gtrsim 10$, as this approach is potentially challenged by the unique conditions of star formation experienced by galaxies at these extreme redshifts. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2403_12683 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Evidence of extreme ionization conditions and low metallicity in GHZ2/GLASS-z12 from a combined analysis of NIRSpec and MIRI observations Calabro, Antonello Castellano, Marco Zavala, Jorge A. Pentericci, Laura Haro, Pablo Arrabal Bakx, Tom J. L. C. Burgarella, Denis Casey, Caitlin M. Dickinson, Mark Finkelstein, Steven L. Fontana, Adriano Llerena, Mario Mascia, Sara Merlin, Emiliano Mitsuhashi, Ikki Napolitano, Lorenzo Paris, Diego Perez-Gonzalez, Pablo G. Roberts-Borsani, Guido Santini, Paola Treu, Tommaso Vanzella, Eros Astrophysics of Galaxies GHZ2/GLASS-z12 has been recently observed by JWST with both NIRSpec and MIRI spectrographs, making it the most distant galaxy ($z_{spec}=12.34$) with complete spectroscopic coverage from rest-frame UV to optical. It is identified as a strong CIV$_{1549}$ emitter with many detected emission lines (NIV], HeII, OIII], NIII], CIII], [OII], [NeIII], [OIII], and H$α$), including a remarkable OIII$_{1333}$ Bowen fluorescence line. We analyze in this paper the joint NIRSpec+MIRI spectral data set. Combining six optical diagnostics (R2, R3, R23, O32, Ne3O2, and Ne3O2Hd), we find extreme ionization conditions, with O32 $=1.39 \pm 0.19$ and Ne3O2 $=0.37 \pm 0.18$ in stark excess compared to typical values in the ISM at lower redshifts. These line properties are compatible either with an AGN or with a compact, dense star-forming environment ($Σ_{\rm SFR}$ $\sim 10^2$-$10^3$ Msun/yr/kpc$^2$), with a high ionization parameter ($\log_{10}$(U) $=-1.75 \pm 0.16$), a high ionizing photon production efficiency $\log(ξ_{\rm ion}) = 25.7_{-0.1}^{+0.2}$, and a low, although not pristine, metal content between $5\%$ and $11\%$ Z$_\odot$ (confirmed by the T$_e$ method), indicating a rapid metal enrichment in the last few Myrs. These properties also suggest that a substantial amount of ionizing photons ($\sim 10\%$) are leaking outside. The general lessons learned from GHZ2 are the following: (i) the UV to optical combined nebular indicators are broadly in agreement with UV-only or optical-only indicators. (ii) UV+optical diagnostics fail to discriminate between an AGN and star-formation in a low metallicity, high density, and extreme ionization environment. (iii) comparing the nebular line ratios with local analogs may be approaching its limits at $z \gtrsim 10$, as this approach is potentially challenged by the unique conditions of star formation experienced by galaxies at these extreme redshifts. |
| title | Evidence of extreme ionization conditions and low metallicity in GHZ2/GLASS-z12 from a combined analysis of NIRSpec and MIRI observations |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2403.12683 |