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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/2507.17057 |
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| _version_ | 1866908462060929024 |
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| author | Berg, Danielle A. Sanders, Ryan L. Shapley, Alice E. Topping, Michael W. Reddy, Naveen A. Skillman, Evan D. Aver, Erik Cullen, Fergus Donnan, Callum T. Dunlop, James S. Jones, Tucker Khostovan, Ali Ahmad McLeod, Derek J. Narayanan, Desika Oesch, Pascal A. Pahl, Anthony J. Pettini, Max Schreiber, N. M. Förster Stark, Daniel P. |
| author_facet | Berg, Danielle A. Sanders, Ryan L. Shapley, Alice E. Topping, Michael W. Reddy, Naveen A. Skillman, Evan D. Aver, Erik Cullen, Fergus Donnan, Callum T. Dunlop, James S. Jones, Tucker Khostovan, Ali Ahmad McLeod, Derek J. Narayanan, Desika Oesch, Pascal A. Pahl, Anthony J. Pettini, Max Schreiber, N. M. Förster Stark, Daniel P. |
| contents | We present the first robust helium (He) abundance measurements in star-forming galaxies at redshifts $1.6\lesssim z\lesssim 3.3$ using deep, moderate-resolution JWST/NIRSpec spectroscopy from the AURORA survey. We establish a High$-z$ HeI Sample consisting of 20 galaxies with multiple high-S/N ($>5σ$) HeI emission-line detections, including the critical near-infrared $λ$10833 line. This is the first study at high redshift leveraging $λ$10833 to break degeneracies between temperature, electron density, optical depth, and He$^+$/H$^+$, enabling reliable He abundance determinations in the early universe. We use a custom MCMC framework incorporating direct-method electron temperature priors, extended optical depth ($τ_{\lambda3890}$) model grids up to densities of $10^6$~cm$^{-3}$, and simultaneous fits of the physical conditions and HeI/HI line ratios to derive ionic He$^+$/H$^+$ abundances. Most of the AURORA galaxies follow the extrapolated $z\sim0$ He/H-O/H trend, indicating modest He enrichment by $z\sim2-3$. However, we identify a subpopulation of four galaxies that exhibit elevated He mass fractions ($ΔY>0.03$) without corresponding enhancements in N/O or $α$-elements ($\sim20$% of the sample). This abundance pattern is inconsistent with enrichment from asymptotic giant branch stars, but favors early He enrichment from very massive stars (VMSs; $M\gtrsim100\ M_\odot$), which can eject He-rich, N-poor material via stellar winds and binary stripping in young stellar populations. We speculate that these elevated-He systems may represent an early phase of globular cluster (GC) formation where N enrichment is still lagging behind He production. This work demonstrates the power of JWST multi-line HeI spectroscopy for tracing early stellar feedback, enrichment pathways, and GC progenitor signatures in the high-z universe. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2507_17057 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | The AURORA Survey: Robust Helium Abundances at High Redshift Reveal A Subpopulation of Helium-Enhanced Galaxies in the Early Universe Berg, Danielle A. Sanders, Ryan L. Shapley, Alice E. Topping, Michael W. Reddy, Naveen A. Skillman, Evan D. Aver, Erik Cullen, Fergus Donnan, Callum T. Dunlop, James S. Jones, Tucker Khostovan, Ali Ahmad McLeod, Derek J. Narayanan, Desika Oesch, Pascal A. Pahl, Anthony J. Pettini, Max Schreiber, N. M. Förster Stark, Daniel P. Astrophysics of Galaxies We present the first robust helium (He) abundance measurements in star-forming galaxies at redshifts $1.6\lesssim z\lesssim 3.3$ using deep, moderate-resolution JWST/NIRSpec spectroscopy from the AURORA survey. We establish a High$-z$ HeI Sample consisting of 20 galaxies with multiple high-S/N ($>5σ$) HeI emission-line detections, including the critical near-infrared $λ$10833 line. This is the first study at high redshift leveraging $λ$10833 to break degeneracies between temperature, electron density, optical depth, and He$^+$/H$^+$, enabling reliable He abundance determinations in the early universe. We use a custom MCMC framework incorporating direct-method electron temperature priors, extended optical depth ($τ_{\lambda3890}$) model grids up to densities of $10^6$~cm$^{-3}$, and simultaneous fits of the physical conditions and HeI/HI line ratios to derive ionic He$^+$/H$^+$ abundances. Most of the AURORA galaxies follow the extrapolated $z\sim0$ He/H-O/H trend, indicating modest He enrichment by $z\sim2-3$. However, we identify a subpopulation of four galaxies that exhibit elevated He mass fractions ($ΔY>0.03$) without corresponding enhancements in N/O or $α$-elements ($\sim20$% of the sample). This abundance pattern is inconsistent with enrichment from asymptotic giant branch stars, but favors early He enrichment from very massive stars (VMSs; $M\gtrsim100\ M_\odot$), which can eject He-rich, N-poor material via stellar winds and binary stripping in young stellar populations. We speculate that these elevated-He systems may represent an early phase of globular cluster (GC) formation where N enrichment is still lagging behind He production. This work demonstrates the power of JWST multi-line HeI spectroscopy for tracing early stellar feedback, enrichment pathways, and GC progenitor signatures in the high-z universe. |
| title | The AURORA Survey: Robust Helium Abundances at High Redshift Reveal A Subpopulation of Helium-Enhanced Galaxies in the Early Universe |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2507.17057 |