# JADES: Differing assembly histories of galaxies -- Observational evidence for bursty SFHs and (mini-)quenching in the first billion years of the Universe

**Authors:** Tobias J. Looser, Francesco D'Eugenio, Roberto Maiolino, Sandro Tacchella, Mirko Curti, Santiago Arribas, William M. Baker, Stefi Baum, Nina Bonaventura, Kristan Boyett, Andrew J. Bunker, Stefano Carniani, Stephane Charlot, Jacopo Chevallard, Emma Curtis-Lake, A. Lola Danhaive, Daniel J. Eisenstein, Anna de Graaff, Kevin Hainline, Zhiyuan Ji  
**arXiv:** [2306.02470](https://arxiv.org/abs/2306.02470)  
**Date:** 2023-06-04  
**Summary page:** https://www.summarizepaper.com/en/paper/2306.02470v1/

## Key points

- A recent study used deep NIRSpec spectroscopic data from the JADES survey to investigate the star formation histories (SFHs) of 200 galaxies at redshifts ranging from 0.6 to 11 and spanning stellar masses from $\rm 10^6$ to $\rm 10^{9.5}~M_\odot$
- High-redshift galaxies, those above the Main Sequence (MS), and low-mass galaxies tend to host younger stellar populations than their low-redshift, massive, and below-MS counterparts
- The correlation between age, M$_*$ and SFR existed even earlier than Cosmic Noon, out to the earliest cosmic epochs
- High-redshift and low-mass galaxies have particularly bursty SFHs while more massive and lower-redshift systems evolve more steadily
- Evidence for another (mini-)quenched galaxy at z = 4.4 in addition to one reported by Looser et al. in 2023 at z=7.3 was presented
- There was a steady decline of dust reddening of the stellar population approaching the earliest cosmic epochs; however, some dust reddening is still observed in some of the highest redshift and most star-forming systems
- This study provides observational evidence for differing assembly histories of galaxies with bursty SFHs and (mini-)quenching occurring in the first billion years of the Universe
- The findings highlight the importance of considering burstiness when studying galaxy evolution and formation as it can lead to temporary quiescence or extended periods of star formation activity depending on environmental conditions such as mass or redshift

## Summary

In a recent study, the authors used deep NIRSpec spectroscopic data from the JADES survey to investigate the star formation histories (SFHs) of 200 galaxies at redshifts ranging from 0.6 to 11 and spanning stellar masses from $\rm 10^6$ to $\rm 10^{9.5}~M_\odot$. The results showed that high-redshift galaxies, those above the Main Sequence (MS), and low-mass galaxies tend to host younger stellar populations than their low-redshift, massive, and below-MS counterparts. Interestingly, this correlation between age, M$_*$ and SFR existed even earlier than Cosmic Noon, out to the earliest cosmic epochs. To explore further the burstiness of SFHs, the authors used a ratio between SFR averaged over the last 10 Myr and averaged between 10 Myr and 100 Myr before observation ($\mathrm{SFR_{cont, 10}/SFR_{cont, 90}}$). The findings revealed that high-redshift and low-mass galaxies have particularly bursty SFHs while more massive and lower-redshift systems evolve more steadily. The study also presented evidence for another (mini-)quenched galaxy at z = 4.4 in addition to one reported by Looser et al. in 2023 at z=7.3. This discovery suggests that some galaxies might be only temporarily quiescent due to extremely bursty evolution. Furthermore, there was a steady decline of dust reddening of the stellar population approaching the earliest cosmic epochs; however, some dust reddening is still observed in some of the highest redshift and most star-forming systems. Overall, this study provides observational evidence for differing assembly histories of galaxies with bursty SFHs and (mini-)quenching occurring in the first billion years of the Universe. The findings highlight the importance of considering burstiness when studying galaxy evolution and formation as it can lead to temporary quiescence or extended periods of star formation activity depending on environmental conditions such as mass or redshift.