Understanding why galaxies stop forming stars

We will then compare the local environment and images of truly “dead” galaxies to those with hidden star formation, to understand the physical processes behind complete cessation of star formation.

The project will use radio observations from the Evolutionary Map of the Universe (EMU), a major new survey with the ASKAP radio telescope. Radio offers a major advantage over optical observations, because it can detect low levels of hidden star formation. The project will measure both the recent history of star formation and any remaining levels of star formation by combining EMU with:

• very large optical spectroscopic surveys such as GAMA, 6dF and DESI
• infrared imaging from the Euclid satellite.

The key innovation of this project is the combination of radio measurements with optical spectroscopy and infrared imaging, combining knowledge, datasets and methods available in the two groups at Macquarie and St Andrews. This multiwavelength approach allows the same galaxy to be studied in several independent ways:

• optical spectra reveal when star formation shut down
• radio data reveal any hidden star formation
• infrared observations trace obscuration caused by dust (large molecular granules) that may hide star formation from view.

By combining large survey datasets in a new way, this project will provide the clearest test yet of how galaxies rapidly stop making stars, or whether dust has led us to misunderstand this important phase of galaxy evolution.

This project will be co-supervised by:

• Professor Vivienne Wild (St Andrews)
• Professor Andrew Hopkins (Macquarie).