# Direct signatures of the formation time of galaxies

**Authors:** Yaniv Donath, Matthew Lewandowski, Leonardo Senatore  
**arXiv:** [2307.11409](https://arxiv.org/abs/2307.11409)  
**Date:** 2023-07-21  
**Summary page:** https://www.summarizepaper.com/en/paper/2307.11409v1/

## Key points

- Study explores measuring the formation time of galaxies using large-scale structure
- Distribution of galaxies on a large scale can provide insights into formation time
- Researchers derive recursion relations for bias expansion for galaxy density
- Enhances understanding of how galaxies form and evolve within cosmic web
- Findings have implications for understanding galaxy formation and evolution
- Direct measurement of formation time provides insights into evolutionary processes
- Contributes to observational cosmology efforts and refines models and theories

## Summary

In their study titled "Direct signatures of the formation time of galaxies," authors Yaniv Donath, Matthew Lewandowski, and Leonardo Senatore explore the possibility of directly measuring the formation time of galaxies using large-scale structure. They demonstrate that the distribution of galaxies on a large scale can provide insights into whether galaxies form over a narrow period before their observed times or are formed over a time scale comparable to the age of the Universe. The researchers derive simple recursion relations for the perturbative terms of the most general bias expansion for galaxy density. This extension allows them to fully apply the well-known dark matter recursion relations to generic tracers. By doing so, they enhance our understanding of how galaxies form and evolve within the cosmic web. The findings presented in this study have significant implications for our understanding of galaxy formation and evolution. The ability to measure the formation time of galaxies directly provides valuable insights into their evolutionary processes and sheds light on fundamental questions about cosmic structure formation. This research contributes to ongoing efforts in observational cosmology and helps refine our models and theories regarding galaxy formation.