# CEERS Key Paper VII: Emission Line Ratios from NIRSpec and NIRCam Wide-Field Slitless Spectroscopy at z>2

**Authors:** Bren E. Backhaus, Jonathan R. Trump, Nor Pirzkal, Guillermo Barro, Steven L. Finkelstein, Pablo Arrabal Haro, Raymond C. Simons, Jessica Wessner, Nikko J. Cleri, Michaela Hirschmann, Micaela B. Bagley, David C. Nicholls, Mark Dickinson, Jeyhan S. Kartaltepe, Casey Papovich, Dale D. Kocevski, Anton M. Koekemoer, Laura Bisigello, Anne E. Jaskot, Ray A. Lucas  
**arXiv:** [2307.09503](https://arxiv.org/abs/2307.09503)  
**Date:** 2023-07-18  
**Summary page:** https://www.summarizepaper.com/en/paper/2307.09503v1/

## Key points

- CEERS utilizes the James Webb Space Telescope's NIRCam WFSS and NIRSpec to study 155 galaxies at redshifts greater than 2
- The study focuses on changes in Ha, [OIII]/Hb, and [NeIII]/[OII] emission lines with redshift
- Blind NIRCam grism observations allow inclusion of galaxies with bright emission lines not observed on NIRSpec masks
- Significant correlation found between [OIII]/Hb and redshift (exceeding 3σ significance level)
- Marginal correlation found between [NeIII]/[OII] and redshift (2σ significance level)
- Emission-line ratios ([OIII]/Hb and [NeIII]/[OII]) show correlations with Hb SFR and anti-correlations with stellar mass across the redshift range of 0<z<9
- Observed trends consistent with lower metallicity and higher ionization levels in low-mass galaxies with high SFR
- IllustriousTNG predictions effectively describe highest [OIII]/Hb ratios without requiring significant shock ionization components from MAPPINGS models
- Study provides insights into changes in emission line ratios with redshift and their correlations with stellar mass and Hb SFR

## Summary

In the Cosmic Evolution Early Release survey (CEERS), we utilize the James Webb Space Telescope's Near-Infrared Camera Wide Field Slitless Spectroscopy (NIRCam WFSS) and Near-Infrared spectrograph (NIRSpec) to study 155 galaxies at redshifts greater than 2. By measuring the rest-frame optical emission-line, we aim to understand the changes in emission line ratios with redshift. The blind NIRCam grism observations allow us to include a sample of galaxies with bright emission lines that were not observed on the NIRSpec masks. We specifically focus on studying the changes in Ha, [OIII]/Hb, and [NeIII]/[OII] emission lines as a function of redshift. To do this, we compare our findings with lower redshift SDSS and CLEAR samples. Our analysis reveals a significant correlation between [OIII]/Hb and redshift, with a significance level exceeding 3σ. On the other hand, we find a marginal correlation between [NeIII]/[OII] and redshift at a significance level of 2σ. To gain further insights into these trends, we compare the emission-line ratios ([OIII]/Hb and [NeIII]/[OII]) with stellar mass and Hb star formation rate (SFR). Our results indicate that both emission-line ratios exhibit correlations with Hb SFR and anti-correlations with stellar mass across the redshift range of 0<z<9. By comparing our findings with MAPPINGS~V models, we infer that these observed trends are consistent with lower metallicity and higher ionization levels in low-mass galaxies exhibiting high SFR. Additionally, when comparing our results to IllustriousTNG predictions, we find that they effectively describe the highest [OIII]/Hb ratios observed in our sample without requiring significant shock ionization components from MAPPINGS models. In conclusion, our study provides valuable insights into the changes in emission line ratios with redshift and their correlations with stellar mass and Hb SFR. These findings contribute to our understanding of the physical properties and evolution of galaxies at high redshifts.