# Relatively young thick discs in low-mass star-forming late-type galaxies

**Authors:** Natascha Sattler, Francesca Pinna, Sebastien Comerón, Marie Martig, Jesus Falcón-Barroso, Ignacio Martín-Navarro, Nadine Neumayer  
**arXiv:** [2410.05761](https://arxiv.org/abs/2410.05761)  
**Date:** 2024-10-08  
**Summary page:** https://www.summarizepaper.com/en/paper/2410.05761v1/

## Key points

- Study focuses on evolution of eight edge-on star-forming disc galaxies with low stellar masses
- Thick discs are older, more metal-poor, and more [Mg/Fe]-enhanced compared to thin discs
- Small age difference (around 2 Gyr) between thin and thick discs
- Thick discs in low-mass galaxies found to be younger than in more massive, quiescent galaxies
- Both thin and thick discs exhibit mostly sub-solar metallicities with milder vertical metallicity gradient
- Star formation histories of thick discs extend down to recent times, but most mass in young stars formed in thin discs
- Thick discs evolved slowly over an extended period rather than forming quickly at high redshift
- Larger mass fraction created in very recent times for both thin and thick discs

## Summary

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This study traces the evolution of eight edge-on star-forming disc galaxies with relatively low stellar masses (4 $\times$ 10$^9$ to 6 $\times$ 10$^{10}$ $M_{\odot}$) by analyzing their thin and thick discs' stellar population properties. Using Multi-Unit Spectroscopic Explorer (MUSE) observations and full-spectrum fitting, we produced spatially resolved maps of ages, metallicities, and [Mg/Fe]-abundances to extract the star formation histories of the stellar discs. Our findings reveal that the thick discs in these galaxies are generally older, more metal-poor, and more [Mg/Fe]-enhanced compared to the thin discs. However, there is only a small age difference (around 2 Gyr) between thin and thick discs. Surprisingly, the thick discs were found to be younger than previously observed in more massive and quiescent galaxies. Both thin and thick discs exhibit mostly sub-solar metallicities, with a milder vertical metallicity gradient than seen in similar studies. The differences in [Mg/Fe] between thick and thin discs are not distinct. Interestingly, we observe that the star formation histories of thick discs extend down to recent times, although most of the mass in young stars was formed in thin discs. These results suggest that the thick discs in these low-mass star-forming late-type galaxies did not form quickly at high redshift but rather evolved slowly over an extended period. Additionally, while both thin and thick discs formed slowly overall, a larger mass fraction was created in very recent times. Overall, our study provides new insights into the formation mechanisms of thin and thick discs in low-mass star-forming late-type galaxies. The unique characteristics observed in these galaxies challenge previous assumptions about the nature of thick disc formation and highlight the importance of studying a diverse range of galaxy morphologies and masses to gain a comprehensive understanding of galactic evolution.