Circumgalactic and Intergalactic Medium
Using world-leading facilities, we’re investigating the gas reservoirs around galaxies that form new stars.
The evolution of galaxies is directly linked to the gas reservoirs surrounding them, known as the circumgalactic medium (CGM). The CGM is a massive multiphase gas reservoir that resides within the virial radius of their galaxies.
Simulations and observations predict that the CGM flows into galaxies along filaments from the intergalactic medium (IGM) providing fuel to form new stars. Stars lose mass as they evolve and many stars explode as supernovae and gas is ejected, feeding back into the CGM/IGM.
This feedback loop continuously shapes a galaxy’s morphology, growth and chemical make-up. Understanding the cycle of how gas is fed into and expelled out of galaxies through the CGM is critical in determining how galaxies form and evolve.
Due to the diffuse and extended nature of the CGM and IGM, the gas cannot be observed using current imaging techniques. The CGM/IGM is only detected in spectra of bright background objects, such as pulsars, fast radio bursts, quasars, and galaxies, which are used to measure the abundance, chemical composition, kinematics, and ionisation state of gas surrounding foreground galaxies.
Given the difficulty of observing this gas, our astronomers use world-leading facilities such as the Keck Observatory, the Hubble Space Telescope, the European Southern Observatory and the Australian Square Kilometre Array Pathfinder. We also use a range of cutting-edge cosmological simulations to interpret our observations of the CGM and IGM.
Our astronomers have used the techniques and facilities mentioned above to study the amount of gas and its relationship to their galaxies from z=0-6. We have also discovered the missing baryons in the universe and measured the size or mass of gas systems called damped Lyman alpha systems that are believed to be galaxies in formation. They explore how CGM metallicities, kinematics, galaxy orientations and environment can be used to infer the origins of the gas.
The CGM is also being used to test our understanding of physics by determining whether fundamental constants vary with location, density and time. Finally, we are pushing the observational limits by conducting direct spectral-imaging of outflows and the CGM near galaxies.
Did you know?
Our current understanding of physics may actually vary with time. Our astronomers are using the European Southern Observatory to place the world’s best constraints on how much the fundamental constants can vary with space and time.
Our projects
UVES SQUAD: The UVES Spectral Quasar Absorption Database
UVES SQUAD is the largest set of high-resolution quasar spectra, built from the data archives of the UVES instrument on the 8-metre Very Large Telescope, and has contributed to a wide array of cosmology, quasar and circumgalactic/intergalactic medium studies so far.
Discovering remnants of the first stars
Within spectra of distant quasars from the world's best optical telescopes, we are discovering rare, almost pristine gas clouds that may have been enriched with the metallic debris from the explosions of the universe's first stars.
Linking the circumgalactic medium to galaxies
Our Multiphase Galaxy Halos Survey uses both observations and simulations to determine how the CGM influences and drives galaxy evolution.
The physics of gas flows around galaxies at cosmic noon
We are examining the circumgalactic medium at the universe’s epoch of peak star formation in order to address how the evolution of galaxies is influenced by gas flows.
The nature of damped Lyman alpha systems
Detecting damped Lyman alpha systems (DLAs) in sightlines to galaxies, as opposed to quasars done previously, is a new approach that will be used by 30m telescopes in the future able to determine the size, mass and kinematics of DLAs for the first time to understand their nature and to perform 3D neutral hydrogen tomography in the early universe.
Understanding galaxy evolution through HI observations
Using observations from next generation radio telescopes, this project aims to understand the fundamental physical processes affecting galaxy evolution in the local universe including angular momentum, gravitational interactions and hydrodynamical processes.
DUVET Survey
We’re using the faintest spectral features in galaxies to make fundamental constraints on how stars form and impact the galaxy and circumgalactic medium around them.
Our astronomers use world-leading facilities such as the Keck Observatory, the Hubble Space Telescope, the European Southern Observatory and the Australian Square Kilometre Array Pathfinder.
MeerHoGS
The MeerKAT Habitat of Galaxies Survey (MeerHoGS) aims to investigate the role of environment in the baryon cycle of galaxies by combining HI interferometric imaging from the MeerKAT SKA Pathfinder with multiwavelength tracers of stellar mass and star formation.
MeerKAT will enable unprecedented studies of intragroup HI and tidal debris, particularly in group environments.
Fast radio bursts with ASKAP
Co-led at Swinburne, the Commensal Real-time Fast Transient (CRAFT) survey detects and localises fast radio bursts with the ASKAP array to both determine what causes FRBs and use them as cosmological probes.
Ionisation and metals
We are investigating how Lyman-continuum photons escape from star-forming regions and into the intergalactic medium, and how metals escape galaxies, especially in the early universe.
For more information, contact Associate Professor Emma Ryan-Weber.
Fundamental constants in distant galaxies
Using quasars as powerful background beacons, we are searching for cosmological variations in the fundamental constants of nature by studying gas in the outskirts of distant galaxies with the world's best telescopes.
Weighing the universe with deuterium
This project aims to weigh the universe by comparing the amount of hydrogen and its main isotope, deuterium, in distant, almost pristine clouds of gas.
Lyman continuum galaxies - uncovering the sources of reionisation
This project uses the Hubble Space Telescope, Keck Telescope, and other deep imaging and spectroscopy to uncover the sources responsible for the Epoch of Reionisation (EoR) and understand their physics and mechanisms of ionising flux escape.
Our people
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Contact the Centre for Astrophysics and Supercomputing
If you have any questions, or are looking for more information, feel free to contact our office on +61 3 9214 8000 or at contact@astro.swin.edu.au.