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Determining the assembly history of modern day galaxies is an important question for current astrophysics. A large range of complex processes over the last 14 billion years have shaped galaxies as we see them today, but the dominant stellar mass components that describe galaxies are remarkably clear: dispersion supported spheroids and rotationally supported disks.

These two main components contain more than 90% of the stellar mass in the local Universe, and have a broadly equal significance (slightly more mass resides in disks overall). However the significance of these different components depends sensitively on the mass of the system, and the redshift at which the system is observed.

In this project the PhD candidate will use (and help develop) our new in-house galaxy decomposition tool called ProFit (Profile Fit). It has an extensive range of available fitting routines, and is highly flexible in its design. The aim is to understand the dominant structural components of the Universe over a large dynamic range in mass, using data from GAMA and COSMOS surveys to quantify the growth in mass and size over the past 10 billion years.

As well as decomposing the images, we wish to extend ProFit to fit multi-band images simultaneously rather than one band at a time. For this extension the model we fit will be a physical description of a galaxy’s recent star formation history, stellar populations and dust- i.e. we will fit the physics that produces the light we observe, not just the light we observe.


GAMA KiDS image (left) ProFit model (centre) residuals (right)

This project will involve collaboration with a large number of international astronomers, and there is significant scope to visit institutions in Europe to further the aims of the work.