The AURORA Survey: Determining the Production Mechanism for OI λ8449 Emission in Star-forming Galaxies at Cosmic Noon

@misc{clarke2026aurora,
  title = {{The AURORA Survey: Determining the Production Mechanism for OI $\mathbfλ8449$ Emission in Star-forming Galaxies at Cosmic Noon}},
  author = {Leonardo Clarke and Alice E. Shapley and Zhiwei Shao and Massimo Pascale and Ryan L. Sanders and Naveen A. Reddy and Tucker Jones and Harley Katz and Natalie Lam and Shreya Karthikeyan and Callum T. Donnan and Natascha M. Förster Schreiber and Anthony J. Pahl and Danielle A. Berg},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.32045},
  eprint = {2609.32045},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.32045},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - The AURORA Survey: Determining the Production Mechanism for OI λ8449 Emission in Star-forming Galaxies at Cosmic Noon
AU  - Leonardo Clarke
AU  - Alice E. Shapley
AU  - Zhiwei Shao
AU  - Massimo Pascale
AU  - Ryan L. Sanders
AU  - Naveen A. Reddy
AU  - Tucker Jones
AU  - Harley Katz
AU  - Natalie Lam
AU  - Shreya Karthikeyan
AU  - Callum T. Donnan
AU  - Natascha M. Förster Schreiber
AU  - Anthony J. Pahl
AU  - Danielle A. Berg
PY  - 2026
DA  - 2026/09/25
PB  - arXiv
DO  - 10.48550/arxiv.2609.32045
UR  - https://arxiv.org/abs/2609.32045
AB  - We analyze deep JWST/NIRSpec observations of 58 star-forming galaxies at 1.3< z <4.8 in the AURORA survey to investigate the origin of the permitted OI λ8449 emission feature. Based on the detection of OI λ8449 in a stack of objects with non-detections, we infer that this feature is ubiquitous among star-forming galaxies at ∼0.5% the strength of Hα. We additionally compare our results with measurements of this line in local HII regions from the CHAOS survey and star-forming galaxies at z<0.1619 in the DESI survey, finding a similar strength of OI λ8449 relative to Hα in these objects. We evaluate four production mechanisms: recombination, collisional excitation, Lyβ fluorescence, and stellar continuum fluorescence. Of these mechanisms, stellar continuum fluorescence (rather than Lyβ fluorescence) provides the most compelling explanation for the OI λ8449 emission based on the additional detection of the near-infrared OI λ11290 and OI λ13168 emission lines. Adopting physical conditions derived from a stacked composite spectrum, we make predictions for the contribution of the other mechanisms to OI λ8449, determining that recombination, collisional excitation, and Lyβ fluorescence contribute negligibly to this feature. While a simple HII region model using Cloudy reproduces the average observed OI λ8449/Hα ratios in the AURORA sample, future works focused on refining model density profiles will be a valuable step in better explaining the near-infrared OI emission-line strengths.
ER  -