# On the Decline of Star Formation during the Evolution of Galaxies

**Authors:** Adelheid Teklu, Rolf-Peter Kudritzki, Klaus Dolag, Rhea-Silvia Remus, Lucas Kimmig  
**arXiv:** [2307.09526](https://arxiv.org/abs/2307.09526)  
**Date:** 2023-07-18  
**Summary page:** https://www.summarizepaper.com/en/paper/2307.09526v1/

## Key points

- Specific star formation rate in galaxies continuously decreases during their evolution
- Decline is not due to depletion of cold gas, but a decrease in the fraction of gas capable of forming stars
- Authors utilize disk galaxies from Magneticum Pathfinder simulation to investigate this behavior
- Mean density of cold gas regions in disk galaxies decreases over time
- Star-forming regions move towards larger galactic radii where gas density is lower
- Findings support inside-out growth in disk galaxies
- Simulations can be fine-tuned to match observations, but comparing simulations directly to observations is challenging
- Fractions of H2 (molecular hydrogen) can vary depending on different prescriptions used and selection effects must be considered when comparing models to observations
- Study contributes to understanding galaxy evolution and star formation decline during galaxy evolution

## Summary

In a previous study, it was found that the specific star formation rate in galaxies continuously decreases during their evolution. This decline is not due to a depletion of cold gas, but rather a decrease in the fraction of gas capable of forming stars. To further investigate the origin of this behavior, the authors of this paper utilize disk galaxies selected from the cosmological hydrodynamical simulation called Magneticum Pathfinder. By following the evolution of these disk galaxies over time, the researchers discover that the mean density of cold gas regions decreases as well. This decrease is attributed to star-forming regions moving towards larger galactic radii where the gas density is lower. These findings support the idea of inside-out growth in disk galaxies and provide valuable insights into how disk galaxies grow and evolve over time. It is important to note that while simulations can be fine-tuned to match observational results by adjusting various physical parameters and modeling feedback mechanisms or star formation recipes, comparing simulations directly to observations can be challenging. The fractions of H2 (molecular hydrogen) can vary depending on different prescriptions used and selection effects must be taken into account when comparing models to observations. This study highlights the complex interplay between different quantities in simulations and contributes to our understanding of galaxy evolution and star formation decline during galaxy evolution.