Science
My current research interests mainly encompasses the study of star formation in the Local Universe using multiwavelength observations. The central themes are:
The physical processes of star formation and galaxy evolution
We live in a spiral galaxy called the Milky Way. How did we come to be where we are today? How do galaxies like the Milky Way form and evolve? We observe 2 main types of galaxies: spirals and spheroidals. What shapes these galaxies? Many aspects of galaxy evolution (and the evolution of our Universe) depend on the relationship between gas and star formation. We do not observe enough gas in the Early Universe to sustain star formation to our present epoch. Yet star formation is still occurring today. Although a topic of intense research for many years, galaxy formation simulations form too many stars too quickly and over-predict the number of dwarf galaxies when compared to observations. Hence more physical constraints are needed from observational experiments.How do galaxies start and stop forming stars? How does a galaxy regulate its star formation? One of the most promising subjects for the investigation of such evolution are transition-type galaxies such as post-starburst galaxies. Feedback from a galaxy's central supermassive black hole is currently thought to be the reason for the star formation rate slowing down in galaxies. However, the details of the physical mechanisms are still active areas of current research.How do supermassive black holes form and grow in galaxies? The formation timescale of supermassive black holes using current formation theories would require billions of year even though we have observational evidence for the existence of these supermassive black holes when the Universe was less than one billion years old!
How does a galaxy’s environment affect its evolution? Specifically, what is the environmental impact of both gravitational and hydrodynamical interactions of galaxies in groups and clusters in addition to the the stripping between a galaxy’s interstellar medium as it falls into the hot halo of a group or cluster of galaxies? Recently, my collaborators and I discovered a nearby drop-through ring galaxy, NGC 922 which resulted from a high velocity collision of a compact dwarf galaxy with a disk galaxy. Apart from gravitational interactions with neighbouring galaxies, the main effect of the cluster environment on individual cluster galaxies is the interaction between the hot ICM and the ISM of a galaxy. This interaction usually results in ram pressure stripping whereby the dust and gas get stripped out of the galaxy as the galaxy falls towards the cluster centre. More information on our Virgo Cluster survey, VIVA, can be found at VIVA.
Next-generation radio telescopes and surveys (such as the Australian SKA Pathfinder and eventually, the SKA)The future in astronomy lies within radio astronomy. As try to peer further and further back to towards the infancy of our Universe, much of the light we observe is redshifted to longer wavelengths due to the expansion of the Universe. As astronomers around the world work towards the world's largest radio telescope known as the Square Kilometre Array (SKA) many precursor instruments are being built and tested in countries with forefront radio astronomy expertise. In Australia, we are building the Australian SKA Pathfinder (ASKAP)
Citizen science (Galaxy Zoo & Radio Galaxy Zoo) & developing deep learning applications
Automated pattern recognition algorithms are still inferior to the human eye and brain combination. Projects on the Zooniverse allow citizen scientists from around the world to participate in the analysis of active areas of research. Although the outreach and teaching components of these projects are obvious, what is often overlooked is the fact that this is becoming a very effective and efficient tool for professional scientists to process very large amounts of data. I am currently co-leading a project, Radio Galaxy Zoo, to explore the growth of supermassive black holes by studying their radio jets. Until automated algorithms become mature enough to complete pattern recognition tasks reliably, the use of the Zooniverse and citizen scientists provides a complementary technique for dealing with the upcoming deluge of radio data that we can expect from the next generation radio observatories.
Catalogues resulting from citizen science projects such as Radio Galaxy Zoo also amass some of the largest samples that are ideal for training advance deep learning algorithms to help with the immense task of processing and analysis the large quantity of data that will eventuate from future radio facilities!
Am currently part of the MAPS team at UWA.
Main collaborations & surveys
HIPASS : The HI Parkes All-Sky Survey
SINGG : The Survey for Ionization in Neutral Gas Galaxies
SUNGG : The Survey of Ultraviolet emission in Neutral Gas Galaxies
WALLABY : the all-sky HI survey using ASKAP
VIVA : VLA Imaging of Virgo in Atomic Hydrogen
SAMI : IFS survey using the SAMI instrument on
BASS : The BAT AGN Spectroscopic Survey
Galaxy Zoo : Citizen science project on the classification of optical morphology of galaxies
Radio Galaxy Zoo : Citizen science project on the classification of radio morphology of galaxies
GLASS : the GAMA Legacy ATCA Survey of the G23 field at 8 GHz