# The effects of environment on morphological evolution between 0<z<1.2 in the COSMOS Survey

**Authors:** P. L. Capak, R. G. Abraham, R. S. Ellis, B. Mobasher, N. Z. Scoville, K. Sheth, A. Koekemoer  
**arXiv:** [astro-ph/0703668](https://arxiv.org/abs/astro-ph/0703668)  
**Date:** 2007-03-26  
**Summary page:** https://www.summarizepaper.com/en/arxiv-id/astro-ph--0703668v1/

## Key points

- Study title: "The effects of environment on morphological evolution between 0<z<1.2 in the COSMOS Survey"
- Authors: P. L. Capak, R. G. Abraham, R. S. Ellis, B. Mobasher, N. Z. Scoville, K. Sheth, A. Koekemoer
- Methodology: Used data from the COSMOS-ACS survey and previous cluster studies; measured Gini parameter within a Petrosian aperture to identify early-type galaxies and eliminate systematic effects
- Rapid transformation of galaxies from late to early types in dense regions compared to sparse ones
- Proportion of early-type galaxies increases over time at a given density with higher growth rate in denser regions (power law index of $0.29\pm0.02$)
- No significant evolution observed for densities below 100 galaxies per Mpc$^{2}$ at redshifts above 0.4
- Strong evolution in star-formation-density relation across all densities and redshifts
- Environmental factors influence galaxy morphology evolution within the cosmic timeline
- Interplay between density, redshift, and galaxy type transitions shapes understanding of galactic evolutionary processes

## Summary

The study "The effects of environment on morphological evolution between 0<z<1.2 in the COSMOS Survey" by P. L. Capak, R. G. Abraham, R. S. Ellis, B. Mobasher, N. Z. Scoville, K. Sheth, and A. Koekemoer explores the impact of environmental factors on galaxy morphology evolution using data from the COSMOS-ACS survey and previous cluster studies. By measuring the Gini parameter within a Petrosian aperture, they accurately identify early-type galaxies across different redshifts and eliminate systematic effects. Their findings reveal a rapid transformation of galaxies from late (spiral and irregular) to early (E+S0) types in dense regions compared to sparse ones. The study demonstrates that at a given density, the proportion of early-type galaxies steadily increases over time with a growth rate that is higher in denser regions following a power law index of $0.29\pm0.02$. Interestingly, no significant evolution is observed for densities below 100 galaxies per Mpc$^{2}$ at redshifts above 0.4. Furthermore, while there is strong evolution in the star-formation-density relation across all densities and redshifts indicating distinct mechanisms driving morphological and star formation transformations; photometric redshifts prove effective in assessing local galaxy environments—although limited by errors for densities exceeding $\Sigma=3$ galaxies per Mpc$^{2}$. This comprehensive analysis sheds light on how environmental factors influence galaxy morphology evolution within the cosmic timeline and highlights the intricate interplay between density, redshift, and galaxy type transitions in shaping our understanding of galactic evolutionary processes.