Building the red sequence through gas-rich major mergers

TL;DR

This paper investigates how gas-rich major mergers contribute to the formation of the red sequence in galaxies, using simulations and observational spectra to quantify their role in galaxy evolution.

Contribution

It demonstrates that a significant portion of red sequence growth occurs through gas-rich major mergers, supported by spectral analysis of galaxy surveys.

Findings

40% of mass flux onto the red sequence involves post-starburst phases

Gas-rich major mergers significantly contribute to red sequence buildup

Spectral analysis confirms the importance of post-starburst galaxies in galaxy evolution

Abstract

Understanding the details of how the red sequence is built is a key question in galaxy evolution. What are the relative roles of gas-rich vs. dry mergers, major vs. minor mergers or galaxy mergers vs. gas accretion? In Wild et al. 2009 we compare hydrodynamic simulations with observations to show how gas-rich major mergers result in galaxies with strong post-starburst spectral features, a population of galaxies easily identified in the real Universe using optical spectra. Using spectra from the VVDS deep survey with z~0.7, and a principal component analysis technique to provide indices with high enough SNR, we find that 40% of the mass flux onto the red-sequence could enter through a strong post-starburst phase, and thus through gas-rich major mergers. The deeper samples provided by next generation galaxy redshift surveys will allow us to observe the primary physical processes responsible for the shut-down in starformation and build-up of the red sequence.