The origins of galaxy bimodality:

mergers, starbursts and feedback in observations and simulations

The project

How galaxies form and evolve is one of the outstanding questions of modern astrophysics. Large surveys are providing an increasingly detailed census of both local and distant galaxies. Considerable progress is being made on quantifying the changing demographics of the galaxy population over the majority of the age of the Universe. Massive numerical simulations have revealed the “hierarchical” nature of structure formation, in the dark matter at least, with small dark matter halos coalescing to form larger gravitationally bound systems. Such simulations have had good success in reproducing the spatial distribution of galaxies observed in large surveys. However, the complex array of physical processes that affect baryons within the dark matter halos, (e.g. gas heating and cooling, star formation, feedback, torques and drag) has so far prevented us from building a comprehensive understanding of how and why galaxies grow and change over time.
This project is about understanding the physical processes responsible for changing galaxies from the irregular balls of gas observed at high redshift, into the bimodal population of star-forming spirals and quiescent ellipticals seen around us today. The objective is to understand galaxy evolution by revealing why are some galaxies in the local Universe forming stars, while others are “red and dead”.

The team

Vivienne Wild

Vivienne Wild - Team Leader


Jairo Mendez-Abreu - Post-doc: galaxy morphologies and dynamics


Kate Rowlands - Post-doc: galaxy SEDs, dust and gas emission


Joao Ferreira - PhD student (Sep 2011) - galaxy evolution models at z~1-2


Milena Pawlik - PhD student (Sep 2012) - image analysis of post-mergers

Datasets and Facilities

• Low-z optical IFS survey CALIFA
• Intermediate z optical spectroscopy+multiwavelength photometry GAMA
• High z multiwavelength photometry CANDELS
• Local reference SDSS
• Purpose built 384 core processor cluster
• GALICS galaxy evolution model (with J. Blaizot)
• SPH galaxy merger simulations (with Peter Johansson and Jakob Walcher)


Coming soon


SEDmorph project - keynote slides, with movies
Evolution of starburst galaxies - ICRAR + AAO + Mt. Stromlo - Sep/Oct 2012
Leiden - Jan 2013
Imperial College London - Feb 2013