# JADES: Balmer Decrement Measurements at redshifts 4 < z < 7

**Authors:** Lester Sandles, Francesco D'Eugenio, Roberto Maiolino, Tobias J. Looser, Santiago Arribas, William M. Baker, Nina Bonaventura, Andrew J. Bunker, Alex J. Cameron, Stefano Carniani, Stephane Charlot, Jacopo Chevallard, Mirko Curti, Emma Curtis-Lake, Anna de Graaff, Daniel J. Eisenstein, Kevin Hainline, Zhiyuan Ji, Benjamin D. Johnson, Gareth C. Jones  
**arXiv:** [2306.03931](https://arxiv.org/abs/2306.03931)  
**Date:** 2023-06-06  
**Summary page:** https://www.summarizepaper.com/en/paper/2306.03931v1/

## Key points

- JADES survey presents Balmer decrement H$\alpha$/H$\beta$ measurements for 51 galaxies at redshifts z = 4-7
- Study uses JWST/NIRSpec MSA and prism/clear configuration to probe low-mass end of galaxy population
- Correlation between Balmer decrement and Mstar already established at high redshifts, suggesting rapid build-up of dust in moderately massive galaxies
- Lowest-mass galaxies (Mstar = 1-3 x 10^7 Msun) display remarkably low Balmer decrement consistent with case B and indicating very little dust content
- Low observed Balmer decrement may also be partly due to intrinsically lower H$\alpha$/H$\beta$ resulting from extreme conditions of ionized gas in primeval and unevolved systems
- Tentative evidence of correlation between SFR and mass of cold gas, but larger samples needed to distinguish direct/primary correlations from indirect/secondary dependencies at high redshifts
- Study provides valuable insights into galaxy evolution at early cosmic timescales and highlights the importance of advanced telescopes like JWST

## Summary

The JADES survey has presented Balmer decrement H$\alpha$/H$\beta$ measurements for 51 galaxies at redshifts z = 4-7, observed with the JWST/NIRSpec MSA. Leveraging 28-hour long exposures and the efficiency of the prism/clear configuration, the study was able to probe directly the low-mass end of the galaxy population, reaching stellar masses as low as 10^7 Msun. The results indicate that a correlation between Balmer decrement and Mstar is already established at these high redshifts, suggesting a rapid build-up of dust in moderately massive galaxies at such early epochs. Interestingly, the lowest-mass galaxies in this sample (Mstar = 1-3 x 10^7 Msun) display a remarkably low Balmer decrement of 2.88 $\pm$ 0.08, consistent with case B and indicating very little dust content. However, it is important to note that such a low observed Balmer decrement may also partly be due to an intrinsically lower H$\alpha$/H$\beta$, resulting from the extreme conditions of the ionized gas in these primeval and unevolved systems. Furthermore, by comparing the Balmer decrement to continuum-derived star-formation rates (SFR), there is tentative evidence of a correlation between SFR and mass of cold gas; however, larger samples are required to distinguish between direct and primary correlations from indirect and secondary dependencies at such high redshifts. Overall, this study provides valuable insights into galaxy evolution at early cosmic timescales and highlights how observations with advanced telescopes like JWST can help us better understand how galaxies form and evolve over time.