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| Main Authors: | , , , , , , , , , , , , , , , , , , , , , , , , |
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| Format: | Preprint |
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2025
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| Online Access: | https://arxiv.org/abs/2512.02000 |
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| _version_ | 1866915651952574464 |
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| author | Hutchison, Taylor A. Khullar, Gourav Rigby, Jane R. Welch, Brian Florian, Michael K. Sharon, Keren Sierra, Isaac Sarmiento, Julissa Mahler, Guillaume Cleri, Nikko J. Bezanson, Rachel Gladders, Michael D. Bayliss, Matthew B. Karp, Juliana S. M. Berry, Dylan Ross, Alex Rivera-Thorsen, T. Emil Choe, Suhyeon C. Dahle, Håkon Chisholm, John Lambrides, Erini L. Larson, Rebecca L. Olivier, Grace M. Owens, Riley Solhaug, Erik |
| author_facet | Hutchison, Taylor A. Khullar, Gourav Rigby, Jane R. Welch, Brian Florian, Michael K. Sharon, Keren Sierra, Isaac Sarmiento, Julissa Mahler, Guillaume Cleri, Nikko J. Bezanson, Rachel Gladders, Michael D. Bayliss, Matthew B. Karp, Juliana S. M. Berry, Dylan Ross, Alex Rivera-Thorsen, T. Emil Choe, Suhyeon C. Dahle, Håkon Chisholm, John Lambrides, Erini L. Larson, Rebecca L. Olivier, Grace M. Owens, Riley Solhaug, Erik |
| contents | We present NIRSpec/IFS observations of a rest-frame UV-bright, massive ($M_* \sim 10^{10}$ M$_\odot$, $z_{AB}=20.5$) galaxy highly magnified by gravitational-lensing observed just after the end of the epoch of reionization ($z=5.04$, $\barμ\sim90$). With JWST accessing the restframe UV and optical spectrum of this galaxy with high fidelity, we classify this UV-bright galaxy as post-starburst in nature -- due to weak/absent emission lines and strong absorption features -- making this an example of a new class of UV-bright but significantly quenched galaxies being discovered in this epoch. With a median $E(B-V)=0.44\pm0.14$, we identify the presence of stellar absorption across the arc both in Balmer lines and the MgII doublet, indicative of older stellar populations dominated by A stars (and potentially B stars). Using spatially-resolved maps of rest-optical strong emission lines, we find a heterogeneous distribution of nebular metallicities across the arc, potentially hinting at different enrichment processes. With a low median lensing-corrected H$α$ star formation rate of SFR$_{Hα} = 0.024 \pm 0.001$ M$_\odot$ yr$^{-1}$, we find in the most "star-forming" clumps indications of lower ionization (log$_{10}$U $\sim -3.2$), lower nebular metallicities (12+log$_{10}$O/H $\lesssim$ 8.3), and hints of higher densities that suggest a possible recent infall of more pristine (low metallicity) gas onto the galaxy. Investigating the regions with no detectable H$β$ emission, we find (for the first time at $z>5$) signatures of diffuse ionized gas (DIG). Separating DIG from HII regions within a galaxy has predominantly been demonstrated at lower redshifts, where such spatial resolution allows clear separation of such regions -- highlighting the immense power of gravitational lensing to enable studies at the smallest spatial scales at cosmic dawn. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2512_02000 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | JWST & the Waz Arc I: Spatially Resolving the Physical Conditions within a Post-Starburst Galaxy at Redshift 5 with NIRSpec IFS Hutchison, Taylor A. Khullar, Gourav Rigby, Jane R. Welch, Brian Florian, Michael K. Sharon, Keren Sierra, Isaac Sarmiento, Julissa Mahler, Guillaume Cleri, Nikko J. Bezanson, Rachel Gladders, Michael D. Bayliss, Matthew B. Karp, Juliana S. M. Berry, Dylan Ross, Alex Rivera-Thorsen, T. Emil Choe, Suhyeon C. Dahle, Håkon Chisholm, John Lambrides, Erini L. Larson, Rebecca L. Olivier, Grace M. Owens, Riley Solhaug, Erik Astrophysics of Galaxies We present NIRSpec/IFS observations of a rest-frame UV-bright, massive ($M_* \sim 10^{10}$ M$_\odot$, $z_{AB}=20.5$) galaxy highly magnified by gravitational-lensing observed just after the end of the epoch of reionization ($z=5.04$, $\barμ\sim90$). With JWST accessing the restframe UV and optical spectrum of this galaxy with high fidelity, we classify this UV-bright galaxy as post-starburst in nature -- due to weak/absent emission lines and strong absorption features -- making this an example of a new class of UV-bright but significantly quenched galaxies being discovered in this epoch. With a median $E(B-V)=0.44\pm0.14$, we identify the presence of stellar absorption across the arc both in Balmer lines and the MgII doublet, indicative of older stellar populations dominated by A stars (and potentially B stars). Using spatially-resolved maps of rest-optical strong emission lines, we find a heterogeneous distribution of nebular metallicities across the arc, potentially hinting at different enrichment processes. With a low median lensing-corrected H$α$ star formation rate of SFR$_{Hα} = 0.024 \pm 0.001$ M$_\odot$ yr$^{-1}$, we find in the most "star-forming" clumps indications of lower ionization (log$_{10}$U $\sim -3.2$), lower nebular metallicities (12+log$_{10}$O/H $\lesssim$ 8.3), and hints of higher densities that suggest a possible recent infall of more pristine (low metallicity) gas onto the galaxy. Investigating the regions with no detectable H$β$ emission, we find (for the first time at $z>5$) signatures of diffuse ionized gas (DIG). Separating DIG from HII regions within a galaxy has predominantly been demonstrated at lower redshifts, where such spatial resolution allows clear separation of such regions -- highlighting the immense power of gravitational lensing to enable studies at the smallest spatial scales at cosmic dawn. |
| title | JWST & the Waz Arc I: Spatially Resolving the Physical Conditions within a Post-Starburst Galaxy at Redshift 5 with NIRSpec IFS |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2512.02000 |