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Descriptions of Current PhD Research

Rory Fahey -

Ellert.van.der Velden - Utilizing cosmological simulations to model the growth of galaxies and their role in ionizing the universe

Understanding the events during the early universe is still one of the greatest cosmological mysteries that we are facing.
In order to try to understand these events and how they led to the universe we know today, we usually create semi-analytic models. Using semi-analytic models allows us to investigate what happened during the early universe by using the physical knowledge and observations we have today. However, a shared problem with all models is that they usually have a large number of parameters, which combined make up a decently large parameter space.
Only a very small part of this parameter space can potentially create a model realization that would be interesting to look at. One of the most commonly proposed solutions is the usage of MCMC methods, but although they are quite reliable, they can be incredibly slow if evaluating the model takes some time.
For that reason, I am developing an algorithm (based on the Bower et al. 2010 paper) that instead tries to construct an approximation of the model (Meraxes) by only using polynomial terms. Such a model is much faster to evaluate than the model it is based on and allows one to search for interesting parts of parameter space much quicker.

Garry Foran - The Lya project: Understanding galaxy formation and evolution by exploring relationships between the observed properties and environments of galaxies over cosmic time.

Galaxy formation and evolution is one of the major unresolved problems in astrophysics. With the aim of understanding the physical processes behind the appearance and environment of galaxies, I use spectroscopy to study the intrinsic and extrinsic properties of galaxies in the early universe.

Specifically, I am exploring relationships between the Lyman-alpha atomic transition of hydrogen the most prominent feature in the spectra of distant galaxies and internal and external properties such as galactic kinematics and the so-called morphology-density relation.

By investigating the above relationships for two galaxy populations that comprise the bulk of all distant galaxies, and by exploring these relationships over cosmic time, I am aiming to incorporate the understanding we gain into a consistent picture of galaxy evolution from 12 billion years ago to the present day.

Adam Batten - Pollution of the Intergalactic Medium by the First Galaxies

Arianna Dolfi - The formation of lenticular galaxies

Ayushi Mandlik -

Aaron Myszka -

Aditya Parthasarathy - High precision pulsar timing

Nature, more often than not, reveals a truly remarkable way of enabling us humans, to understand her. One of these magical revelations and a gift to astronomers, are Pulsars (which are highly magnetized, rapidly rotating neutron stars with beams of coherent emission from their magnetic dipoles! - how cool is that?).

"Space" and "Time" are a fundamental way of understanding this universe and measuring "time" precisely in interesting and extreme parts of the universe is key, to understanding the behavior of space. Pulsars are clocks that are distributed across the universe, that can be timed precisely to understand the nature of space in those regions. Such studies have enabled us to detect planetary companions around these stars, test theories of gravity, understand the interior structure of neutron stars and also the possibility of detecting gravitational radiation.

My research involves the timing of these marvellous rotating stars and studying their single pulses to mitigate noise and achieve better precision in timing. I will be working in commissioning the MeerKAT radio telescope in South Africa and the new wideband receiver at Parkes, both of which are great for the future of pulsar timing. I would also be involved with the Parkes Pulsar Timing Array (PPTA) team on projects related to pulsar timing and gravitational wave detection. Finally, I would be working on the pulsar timing programme and the automatic scheduling of the Molonglo Radio telescope, which would make it more awesome than it is already!

Supervising me in this already exciting PhD journey are Prof.Matthew Bailes and Dr. Willem van Straten. Along with them, there is an entire team of cool pulsar astronomers who are amazing to work with.

Burak Dogruel -

Brodie Norfolk -

Bronwyn Reichardt Chu -

Cherie Day - Pinpointing the origin of fast radio bursts

The ultimate goal of my contribution to the UTMOST-2D project is to localise Fast Radio Bursts to their host galaxies using the Molonglo Radio Telescope and to use this information not only to determine the types of objects responsible for these short but highly energetic bursts but also as a means of mapping the universe. To accomplish this, new developments in the instrument must be made in order to increase its capabilities. Thus, a substantial part of my project will be to design and construct the signal processing chain for and commission the second arm of the interferometer. With this first-hand knowledge of the instrument, an optimised detection pipeline for the data can be developed as well as the imaging and analysis tools needed to provide burst positions and well-calibrated position uncertainties.

Christian Lehmann -

Chandrashekar Murugeshan - Understanding Galaxy Evolution with Next Generation Radio Telescopes

Neutral hydrogen (HI) studies are important for understanding galaxy evolution since HI is the primary ingredient essential for star formation. HI morphology can tell us a lot about a galaxy’s environment and whether it has likely to have undergone any interaction or merger, and as such the project will also involve parametrising the HI morphologies of galaxies. One of the main goals of my PhD is to study the HI distribution as a function of stellar mass. A trend in the distribution of HI and stellar mass based on the different morphological and optical types would then lead to a distinction in the evolutionary stages of galaxies, thus paving ways to understanding their evolution. I will also examine if environmental effects influence the HI content in galaxies.

Daniel Berke - Are the fundamental constants of nature very truly constant?

Debatri Chattopadhyay - Binary millisecond pulsars and black hole binaries in star clusters

I work on simulating star clusters, looking for black hole and millisecond pulsar binaries in them, their evolution and mergers - which generates gravitational waves. Albert Einstein's General Theory of Relativity predicted almost a century ago, that accelerating masses send ripples through the fabric of space-time, that propagates like a wave with the velocity of light, famously called "Gravitational Waves". The technological advancement has enabled us to detect these waves created by gravitational interactions and mergers of heavy two body systems, and the 2017 Nobel prize in Physics was awarded to for the detection of it.
As a part of OzGrav: The ARC Centre of Excellence for Gravitational Wave Discovery, I look for interesting binary systems and their subsequent merger, which may emit detectable gravitational waves. Star clusters are dense environments which make them the birthplaces and collision hubs for these heavy mass binary systems. These higher mass binaries produce gravitational waves that LIGO and VIRGO can detect and thus, they are interesting members to study in the extreme, dense environment of globular clusters, where dynamical events and collisions are a common occurrence. I also plan to theoretically compute binary evolution and subsequent mergers of black holes and neutron stars by population synthesis. Simulations now run on the Green II: gSTAR and SwinSTAR supercomputer, and in future, will be running on the new OzSTAR supercomputer, currently under installation at Swinburne. Starting my PhD in this new era of astrophysics is really exciting for me, and the future of gravitational waves seems to be limitless. Guiding me through this quest of knowledge are my supervisors Dr. Jarrod Hurley and Dr. Matthew Bailes.

Dian Triani - Modelling the SED evolution of galaxies throughout cosmic time

Modelling of galaxy formation is a process that is tightly coupled with the dark matter simulation. Based on this, on my PhD thesis, I will be supervised by Prof. Darren Croton and Dr. Manodeep Sinha to make predictions for the SED of galaxies throughout its formation timeline.

The modelling of each SED includes modelling of the complex processes of galaxy evolution, such as gas accretion, star formation, supernova feedback, and dust physics. We will try to understand and place these processes into a consistent sequence and create the SED that comes from each. The synthetic SED then will be used to interpret observational results, focusing on the infrared light which is typically observed in the distant universe. This new SED model will enable us to create predictions of galaxy evolution, as probed through its SED, across the entire history of the universe.

Geoffrey Bryan - Dynamical processing and jet entrainment of dust around young stellar objects

The presence of refractory crystalline minerals such as forsterite (Mg2SiO4) in cometary dust and in the relatively un-processed interiors of some kinds of meteorites poses a challenge to the conventional theory of the development of the Solar System. These objects form in relatively cool regions of the accretion disc surrounding young stars, yet crystalline forsterite and its analogues requires processing at high temperature, in the inner part of the accretion disk to form. My PhD project will investigate whether the combination of star-burst eruptions of young stars and dust entraining jet flows (possibly induced by wound-up magnetic fields) is a suitable mechanism for explaining the chemical properties observed in the meteorite population, and satellite sample return missions as well as the infrared observations of young stellar objects.

I have a BSc with Honours in Theoretical Physics and a Masters degree in Engineering Science (thesis title: "On the analysis of axis-symmetric eddy currents" both from Monash University and a Masters degree in Business and Information Technology from the University of Melbourne. I worked in the Australian government's research organisation CSIRO for more than twenty years in diverse roles including: fluid dynamics researcher, IT manager, research administrator and executive officer.

Gurvarinder -

Geray Karademir -

Grace Lawrence -

Hao Ding -

Hasti Nateghi -

James Esdaile - Massive Galaxies in the Early Universe

Juan Salcedo -

Jonah Gannon - TBA

Liyualem Tilahun -

Matthew Miles -

Marcus Lower - Application of astrophysical inference to next-generation pulsar timing data sets

Mohsen Shamohammadi -

Nandini Sahu - Prediction of Gravitational Waves from Galaxy Bulges

Poojan Agrawal - A new paradigm of globular cluster formation with multiple stellar populations

Despite the progress in our computational abilities, combining detailed stellar evolution with codes for modelling clusters and galaxies still remains a challenge. A less accurate but simpler way to achieve the same is the method of defining polynomial fits to the stellar evolution tracks, SSE code developed by Hurley et al in 2000. It has been a popular choice for population synthesis codes for over two decades but the developments in stellar physics, especially for massive stars, have created a pressing need to update them. However, these formulae are not only hard to define but are also less adaptable to changes in stellar tracks.

Hence, a part of my research is to evolve a number of massive stars using Modules for Experiments in Stellar Astrophysics (MESA). Second part is to develop an alternate method based on the numerical interpolation of the stellar tracks which can serve as an alternative to SSE in population synthesis codes. This is important not just from the point of view of understanding stellar properties like chemical abundances and stellar dynamics but also for constraining binary evolution which are important sources of gravitational waves.

Pol Gurri Perez - How to measure what cannot be seen: the dark matter that surrounds galaxies.

The main goal of my PhD is to perform studies of projected galaxy pairs in which some appreciable degree of weak gravitational lensing is taking place. Through bespoke analysis of each individual galaxy-galaxy lensing system, the aim of the PhD is to make direct measurements of the masses and shapes of dark matter halos around individual galaxies.

Pravir Kumar - Localising fast radio bursts with the Australian Square Kilometre Array Pathfinder

Paul Frederic Robert - Pristine Gas in the Early Universe

My main interests are Galaxy Formation and Evolution, and the Intergalactic Medium (IGM). The IGM is the gas between galaxies. It is supposed to be the principal reservoir of normal matter: baryons. Therefore, it plays a crucial part for the formation of the first stars and consequently the first galaxies. It is then very important to probe its properties. However, it doesn’t emit much light. To detect it, we have to rely on the quasar absorption line technique. Quasars are very bright objects that can be seen even at a relatively large distance from us. They shine through the IGM and intervening gas interacts with their emitted light. That process will leave absorption patterns in the quasar’s spectrum collected by a spectrograph. By studying these features, we can infer which elements compose the absorbing gas in the line of sight, physical properties such as velocity distribution, density, temperature, metallicity, ionization state, etc…

My project is oriented toward a particular class of absorbers: the Lyman limit systems (LLS). They are defined by a neutral hydrogen column density, N(HI), such that 17.2 < log(N(HI)/cm2) < 20.3. In the past five years, very metal-poor LLSs, i.e. with almost no metal lines, have been detected (metals here refer elements heavier than helium). The existence of such metal poor, or near-pristine, environments in the vicinity of the IGM is exciting as it could bring more information about the first stars (Pop III stars), and the gas cycle in early structure formation. Pop III stars supposedly appeared in metal-free gas clouds, and their death as supernovae polluted the IGM with metals. Near-pristine absorbers could be remnants of this primordial gas. My aims are to:

I. Identify more of these extremely low metallicity absorbers, either with existing data or future observations.

II. Find explanations for their origin.

Robert Dzudzar - The evolution of gas-rich galaxies in the group environment

This PhD project is under the supervision of Assoc. Prof. Virginia Kilborn, Prof. Gerhardt Meurer and Dr. Sarah Sweet.

During my PhD project I will analyse the star forming properties of galaxies in nearby groups, using observations of their HI content, and current star formation rates. The HI observations are taken from the HI Parkes All Sky Survey (HIPASS) with high-resolution follow-up observations from the Australia Telescope Compact Array (ATCA). The star-forming properties of the galaxies will come from the Survey of Ionization in Neutral Gas Galaxies (SINGG).

Using the high-resolution HI imaging combined with the star formation and stellar properties of the galaxies, I will:

* Determine the star formation efficiency of galaxies in the group environment;

* Investigate the existence of tidal dwarf galaxies in groups;

* Study gas stripping and accretion in the group environment;

* Search for tidal features in the HI gas that indicate interactions are affecting the member galaxies.

Ryan Turner -

Rahul Sengar - Searching for gravitational waves with LIGO and relativistic binary pulsars in radio data

Renee Spiewak - Searches for Millisecond Pulsars and Fast Radio Bursts

PhD Candidate Searching for Millisecond Pulsars - with more to come

Simon Goode -

Suei-Hei (Dexter) Hon -

Sera Rauhut -

Shingo Tanigawa -

Sara Webb - Exploring the high energy dynamic Universe

Uros Mestric - Characterising Lyman Continuum Galaxies

The details surrounding the end of the Epoch of Reionization is one the most topical questions in modern astrophysics. Less than 1 billion years after the Big Bang, the hydrogen gas in the Universe encountered a fundamental phase change and transitioned from a neutral to ionized state. The most likely source of the ionizing radiation behind this change is Lyman-continuum emission escaping from galaxies. The problem is that we only have a fragmented understanding of what types of galaxies provide the most ionizing flux at any point in the history of the Universe. Galaxies at redshifts of 3 to 4 are in a 'sweet spot' for detecting their Lyman-continuum radiation and can inform us of the contribution by galaxies at earlier times. The aim of this PhD project is to measure the escaping flux from galaxies at redshifts of 3 to 4 and to characterise their properties (such as luminosities, morphologies, and emission lines) for the first time.

Vivek Gupta - Mapping the Universe with FRBs

Fast Radio Bursts (FRBs) are very mysterious astrophysical radio signals which most probably are originating outside our own galaxy. FRBs have perplexed astronomers for more than a decade now. To be able to unravel their mystery, we need to detect and localize the source of more and more FRBs. New telescopes are being developed across the globe and old ones are being renovated to achieve this goal.

I will be working towards developing observation strategies and detection algorithms which can be implemented across various observatories in order to maximise their ability to detect and localize FRBs. Further, I shall be analyzing the characteristics of detected FRB signals and trying to work out the physical processes causing them; and the properties of the Intergalactic Medium by decoupling the effect it has on the FRB signal as it travels through it.

Waqas Bashir -