Extragalactic astronomy

Looking beyond the limits of our Milky Way galaxy

Research projects in this area study individual distant galaxies to trace the very structure and evolution of the Universe.

Our researchers work on a range of projects, including surveys mapping tens to thousands of galaxies with:

• optical facilities (Hector, MAGPI, Hi-KIDS)
• radio facilities (ASKAP, WALLABY, EMU)
• using highly energetic transients to probe the material that lies around and between galaxies (eg FRBs).

Learn more about the projects we are undertaking, the researchers engaged in them and who you can contact to get involved.

Environmental regulation of supermassive black hole feedback across the cosmic web

The combination of the Evolutionary Map of the Universe (EMU) survey with the Wide Area VISTA Extragalactic Survey (WAVES) and the 4MOST Hemisphere Survey (4HS) will provide one of the largest and most statistically powerful datasets ever assembled for studying galaxy evolution in the nearby Universe.

Together, these surveys will deliver:

• optical spectroscopy
• radio continuum measurements
• redshifts
• stellar population diagnostics
• environmental information for millions of galaxies spanning a wide range of cosmic environments.

A major open question in galaxy evolution is how radio mode feedback from supermassive black holes (called 'active galactic nuclei', AGN) regulates star formation and whether this process depends primarily on galaxy mass, local environment, halo properties or cosmic web structure.

Radio AGN are preferentially associated with massive galaxies in dense environments, but the mechanisms connecting environment, gas supply and feedback remain uncertain, particularly outside rich clusters and over large cosmological volumes.

This project will investigate how radio AGN activity and degree of star formation vary across filaments, groups, clusters, compared to isolated galaxies. The project will use large statistical samples combining emission line diagnostics, spectral indices, radio luminosities and environmental metrics to determine where and when radio feedback is most effective.

The project builds from targeted low redshift studies before expanding toward population scale analyses enabled by the full surveys, while directly contributing to the understanding of galaxy evolution and black hole growth over cosmic history.

To get involved in this project, contact: Matt Owers

Galaxy evolution through dust and metal cycles

Galaxies evolve through the continuous cycle of gas, metals and dust, the material that forms stars, planets and ultimately the ingredients for life. Understanding how these components are created, redistributed and lost is a central question in astrophysics.

This project will tackle these questions by combining the strengths of Hector and ULTIMATE. Hector provides spatially resolved spectroscopy for large samples of galaxies, capturing global trends in metal enrichment, star formation and dust attenuation. ULTIMATE, with adaptive-optics infrared capability, resolves the small-scale structure of dust and metals within galaxies.

The student will connect these two regimes, linking galaxy-wide properties to internal physical processes, to build a coherent picture of how dust and metals evolve across scales. Working within both collaborations, the student will contribute to data analysis and science exploitation, ensuring that instrument capabilities directly translate into new understanding of galaxy evolution.

With ULTIMATE currently in the build phase, the project also offers opportunities to engage in instrument science, from laboratory characterisation to on-sky commissioning, providing a rare 'lab-to-sky' experience, alongside guaranteed access to Subaru/ULTIMATE observations.

To get involved in this project, contact: Tayyaba Zafar

Galaxy transformation during cluster assembly

Galaxy clusters and filaments are among the most important environments for driving galaxy transformation, yet the physical processes responsible for quenching star formation and triggering radio activity remain incompletely understood. The combination of WAVES or 4HS spectroscopy with ASKAP EMU radio continuum imaging provides a unique opportunity to study these processes simultaneously across unprecedented sky areas and sample sizes.

These surveys will enable the identification of dynamically evolving clusters, infalling galaxy populations and large-scale filamentary structures while also tracing star formation, supermassive black hold activity and diffuse radio emission associated with the intracluster medium.

This project will investigate how cluster assembly and large-scale structure influence galaxy evolution.

Key questions include:

• how rapidly galaxies quench after entering dense environments
• what role cluster dynamics play in triggering radio emission from supermassive black holes or diffuse radio halos and relics
• whether merger driven turbulence or accretion shocks affect star formation activity.

Recent observational studies have revealed growing evidence for preprocessing in filaments and group environments prior to cluster infall, but current samples remain limited in both size and environmental coverage. Using spectroscopic diagnostics from 4MOST together with EMU radio continuum measurements, the project will characterise galaxy populations across a range of dynamical states and environments, from relaxed systems to actively merging clusters.

The project supports a progression from detailed studies of selected systems toward broader statistical analyses as survey datasets mature, while addressing central questions in environmental galaxy evolution.

To get involved in this project, contact: Matt Owers

Gas, dust and metals in the Era of 4MOST: A Data-Driven Approach

The evolution of galaxies is imprinted in their spectra, revealing the presence of dust, metals and gas across cosmic time. Probing this evolution, particularly through bright sightlines such as quasars and gamma-ray bursts (GRBs), allows us to trace the build-up of elements and the conditions of the early universe.

With surveys like ESO 4MOST, astronomy is entering a data-rich era, producing unprecedented volumes of spectroscopic data. This project will develop data-driven and/or machine learning approaches to extract physical insight from these large datasets.

The student will analyse 4MOST observations to measure dust attenuation, chemical enrichment and gas properties in galaxies and along sightlines to quasars and GRBs. A key focus will be building scalable methods to identify patterns and derive physical parameters from high-dimensional data.

Embedded in the 4MOST collaboration, the project will connect big data to fundamental science questions, transforming large survey datasets into a new understanding of how galaxies and the elements within them evolve.

To get involved in this project, contact: Tayyaba Zafar

Measuring galaxy star formation rates

The process of star formation in the Universe is intimately linked to the evolution of galaxies. To understand galaxy properties, researchers typically make assumptions about the distribution of masses in a newly formed population of stars, with the same assumption applying at all times and in all galaxies in the universe.

This 'universal' initial mass function (IMF) is poorly constrained observationally, and there are many results from the past two decades suggesting that the IMF is not universal, that is, it may differ between galaxies and at different epochs in cosmic history.

This project will look at refining the way that observations can be used to constrain measurements of the stellar IMF through development of so-called population synthesis tools, models linking stellar evolution with observational properties of galaxies, in order to identify new observational metrics that may be able to probe the shape and evolution of the IMF in different galaxy populations.

To get involved in this project, contact: Andrew Hopkins

The impact of environment on galaxies as probed by the SAMI and Hector Galaxy surveys

Galaxy properties, such as morphology and rate of star-formation, correlate strongly with the environment in which a galaxy resides. An added complexity to this picture is that the densest regions in the Universe – rich galaxy clusters – are not static but are themselves evolving dynamically by hierarchical structure growth.

Understanding how this environment-driven transformation takes place is one of the fundamental challenges in modern astrophysics.

Various avenues for PhD projects supervised by Dr Matt Owers are available within this field, using data collected during the SAMI Galaxy Survey and preparing for the upcoming Hector Survey. Projects all involve the potential for collaboration with both Australian and international astronomers.

To get involved in this project, contact: Matt Owers

Understanding galaxies near and far with MUSE

MUSE is a revolutionary instrument on the European Southern Observatory (ESO) Very Large Telescope (VLT), which allows us to make detailed maps of the motions and chemistry of gas and stars in galaxies by applying state-of-the art modelling and analysis tools.

Projects in this area will make use of data from one of the following MUSE programs:

• MAGPI – mapping galaxies at a lookback time of four billion years ago
• MAUVE – mapping galaxies in the nearby Virgo galaxy cluster to study environmental impacts
• GECKOS – mapping Milky Way-like galaxies to better understand our galactic cousins.

To get involved in this project, contact: Richard McDermid

Unveiling the connections between gas, stars and star-formation in nearby dwarf galaxies

Existing surveys using Integral Field Spectroscopy (IFS) to provide a detailed view of how galaxies formed and evolved mainly target 'normal' galaxies, but dwarf galaxies tend to be under-represented. In addition, the systems observed are poorly resolved and lack spatially-resolved neutral hydrogen data.

Through the HI - KOALA IFS Dwarf galaxy Survey (Hi-KIDS), we are obtaining 2D optical spectra using the KOALA Integral Field Unit at the 3.9m AAT for nearby dwarf galaxies with available HI interferometric data.

This project will provide expertise with optical IFS and radio data, as well as with data science tools needed for astronomy.

To get involved in this project, contact: Angel Lopez-Sanchez