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

Abstract

We used deep NIRSpec spectroscopic data from the JADES survey to derive the star formation histories (SFHs) of a sample of 200 galaxies at 0.6 < z < 11 that span stellar masses from 106 to 109:5 M⊙. We found that galaxies at high redshift, galaxies above the main sequence (MS), and low-mass galaxies tend to host younger stellar populations than their lower-redshift, below the MS, and more massive counterparts. Interestingly, the correlation between age, stellar massM*, and star formation rate (SFR) existed even earlier than cosmic noon, out to the earliest cosmic epochs. However, these trends have a large scatter. There are also examples of young stellar populations below the MS, which indicates recent (bursty) star formation in evolved systems. We further explored the burstiness of the SFHs by using the ratio of the SFR averaged over the last 10 Myr and averaged between 10 Myr and 100 Myr before the epoch of observation (SFRcont;10/SFRcont;90). We found that high-redshift and low-mass galaxies have particularly bursty SFHs, while more massive and lower-redshift systems evolve more steadily. We also present the discovery of another (mini-)quenched galaxy at z = 4:4, which might be only temporarily quiescent as a consequence of the extremely bursty evolution. Finally, we also found a steady decline in the dust reddening of the stellar population as the earliest cosmic epochs are approached, although some dust reddening is still observed in some of the highest-redshift and most strongly star-forming systems.