# Exploring the evolution of red and blue galaxies in different cosmic web environments using IllustrisTNG simulation

**Authors:** Biswajit Pandey, Anindita Nandi  
**arXiv:** [2410.23896](https://arxiv.org/abs/2410.23896)  
**Date:** 2024-10-31  
**Summary page:** https://www.summarizepaper.com/en/paper/2410.23896v2/

## Key points

- Study title: "Exploring the Evolution of Red and Blue Galaxies in Different Cosmic Web Environments Using IllustrisTNG Simulation" by Biswajit Pandey and Anindita Nandi
- Analysis spans redshift $z=3$ to $z=0
- Otsu's method used for galaxy classification as red or blue at each redshift
- Geometric environments determined based on eigenvalues of deformation tensor
- Initially, blue galaxies more prevalent in clusters compared to filaments, sheets, and voids; shifts at lower redshifts with red fractions increasing earlier in denser environments
- Most massive galaxies ($\log(\frac{M_{*}}{M_{\odot}})>10.5$) quenched across all environments at $z<1$
- Low-mass galaxies ($\log(\frac{M_{*}}{M_{\odot}})<10.5$ show stronger influence from surroundings, clusters host higher proportions of red galaxies at lower redshifts
- Slower mass growth for low-mass galaxies in clusters at $z<1
- Filaments exhibit relative red fractions comparable to clusters for low masses but harbor nearly 60% of low-mass blue galaxies, indicating diverse galaxy population experiencing broader range of evolutionary stages due to less intense environmental quenching
- Clusters display highest relative blue fraction for high-mass galaxies at lower redshifts attributed to interactions or mergers reigniting star formation temporarily
- $(u-r)$ color distribution transitions from unimodal to bimodal by $z=2$ across all environments; clusters exhibit highest median color and lowest median specific star formation rate (sSFR) at $z<1$
- Stellar mass primary driver of color evolution in massive galaxies; complex interplay between mass and environment shapes evolutionary trajectory of low-mass galaxies

## Summary

In the study titled "Exploring the Evolution of Red and Blue Galaxies in Different Cosmic Web Environments Using IllustrisTNG Simulation" by Biswajit Pandey and Anindita Nandi, the authors analyze the evolution of red and blue galaxies from redshift $z=3$ to $z=0$. They utilize Otsu's method to classify galaxies as red or blue at each redshift and determine their geometric environments based on the eigenvalues of the deformation tensor. The analysis reveals an interesting trend where initially, blue galaxies are more prevalent in clusters compared to filaments, sheets, and voids. However, this pattern shifts at lower redshifts, with red fractions increasing earlier in denser environments. At redshifts below $z<1$, it is observed that most massive galaxies ($\log(\frac{M_{*}}{M_{\odot}})>10.5$) are quenched across all environments. On the other hand, low-mass galaxies ($\log(\frac{M_{*}}{M_{\odot}})<10.5$) show a stronger influence from their surroundings, with clusters hosting higher proportions of red galaxies at lower redshifts. Furthermore, the study highlights a slower mass growth for low-mass galaxies in clusters at $z<1$. Filaments exhibit relative red fractions comparable to clusters for low masses but interestingly harbor nearly 60% of low-mass blue galaxies, indicating a diverse galaxy population experiencing a broader range of evolutionary stages due to less intense environmental quenching. Clusters, despite being the densest environment, display the highest relative blue fraction for high-mass galaxies at lower redshifts. This phenomenon is attributed to interactions or mergers that can temporarily reignite star formation in some high-mass galaxies within clusters. The $(u-r)$ color distribution transitions from unimodal to bimodal by $z=2$ across all environments. Notably, at $z<1$, clusters exhibit the highest median color and lowest median specific star formation rate (sSFR), with stellar mass emerging as the primary driver of color evolution in massive galaxies. Overall, this comprehensive analysis suggests that while stellar mass predominantly governs quenching in high-mass galaxies, a complex interplay between mass and environment shapes the evolutionary trajectory of low-mass galaxies. The findings shed light on how different cosmic web environments impact galaxy evolution over cosmic time scales.