CECILIA: Using Flexible Photoionization Models to Accurately Measure Abundances without Auroral Lines

@misc{cuestas2026cecilia,
  title = {{CECILIA: Using Flexible Photoionization Models to Accurately Measure Abundances without Auroral Lines}},
  author = {Nathalie A. Korhonen Cuestas and Allison L. Strom and Yijia Li and Noah S. J. Rogers and Caroline von Raesfeld and Gwen C. Rudie and Ryan F. Trainor and Menelaos Raptis and Zhuyun Zhuang},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.22488},
  eprint = {2609.22488},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.22488},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - CECILIA: Using Flexible Photoionization Models to Accurately Measure Abundances without Auroral Lines
AU  - Nathalie A. Korhonen Cuestas
AU  - Allison L. Strom
AU  - Yijia Li
AU  - Noah S. J. Rogers
AU  - Caroline von Raesfeld
AU  - Gwen C. Rudie
AU  - Ryan F. Trainor
AU  - Menelaos Raptis
AU  - Zhuyun Zhuang
PY  - 2026
DA  - 2026/09/18
PB  - arXiv
DO  - 10.48550/arxiv.2609.22488
UR  - https://arxiv.org/abs/2609.22488
AB  - JWST has facilitated the detection of faint, auroral emission lines needed to directly measure the electron temperature and elemental abundances in high-redshift galaxies. However, such measurements still require substantial observational investment, potentially making self-consistent, population-level studies of direct-method metallicity scaling relations across multiple epochs of Cosmic time prohibitively expensive. Photoionization modeling could allow us to measure metallicity using more routinely-observed emission lines across larger galaxy samples with shallower spectra. We use z∼ 2 galaxies from the CECILIA survey and local galaxies and H II regions from the LBT Y_P Project to compare abundance measurements made via the T_e method to abundances estimated using the novel photoionization modeling code, Cue. Based on the results, we explore the viability of, biases introduced by, and the best practices for measuring gas-phase metallicity with photoionization modeling. We show that Cue can be used to accurately measure O/H while remaining agnostic to the ionizing spectrum and that accurate recovery of O/H can be achieved with relatively bright oxygen and sulfur lines, demonstrating that Cue could be used to measure metallicity in large samples that lack the depth necessary for direct measurements of O/H. However, using sulfur emission lines can also severely bias the results of photoionization modeling in high-redshift galaxies, where non-Solar abundance patterns are common. We make recommendations regarding the use of photoionization models to measure metallicity in local and high-redshift samples and future developments to photoionization modeling methods.
ER  -