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Descriptions of Current PhD Research

Ellert.van.der Velden - Constraining Dark Matter Distributions

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.

Alex Codoreanu - The nature of First Stars

I am working on understanding the absorption profiles observed in the spectra of quasars. Quasars are very bright objects which means that we can observe them from very far away, more than 13 billion years ago in fact or beyond redshift 5. As the light emitted by these bright objects traverses the Universe it passes between galaxies and interacts with the matter in the Inter Galactic Medium, IGM for short. This interaction creates absorption profiles that can tell us about the stars which have "polluted" the IGM.

By putting a lot of these observations together and by studying the relative strengths of different ionization states of Carbon, Oxygen, Silicon and other metals, I will better constrain the stellar population models and their number density in order to better understand the process of reionization of cosmic hydrogen.

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.

Bernard Meade - Coping with the data deluge: Combining remote visualisation and novel interaction techniques with ultra-high resolution displays to maximise the scientific returns of massive astronomy datasets

In my research I am looking at the challenges facing astronomy researchers in dealing with ever-increasing datasets. I am combining remote visualisation tools such as cloud computing with ultra-high resolution displays to improve research potential.

Caitlin Adams - Testing the cosmological model in the low-redshift Universe

Data from the low-redshift Universe can play a key role in testing cosmological models. Specifically, measurements of the peculiar velocities of galaxies can be used to probe gravitational physics on large scales. This allows tests of modified gravity models, which predict deviations from General Relativity, and may provide an alternative explanation for dark energy. The limited survey volume of low-redshift surveys leads to high sample variance, but it has been theorised that this can be mitigated by cancelling sample variance between the velocity and density fields of the survey. In this PhD, I will apply this theoretical approach to data from the 6 degree Field Galaxy Survey, with the aim to test modified gravity models.

Chris Curtin - Super-Luminous Supernovae - DB Covering the deaths of the first stars

I am part of the Survey Using DECam for Superluminous Supernovae (SUDSS). We are trying to create a large sample of superluminous supernovae for statistics and followup.

I use a technique which filters out all objects but Lyman break galaxies in order to filter my supernova detections to only those in the redshift range from 2-4. These are extremely distant supernovae by the technological standards of today.
At this large redshift, theory suggests that we will find an over abundance of the so called pair-instability supernova (PISN). These supernovae need to originate from stars which were very massive and very metal poor. These are precisely the conditions we expect to see at high redshift. The existence of this type of supernova remains in question, however there are candidates that have been observed in archival data.
PISNe, if confirmed, would constitute an excellent way to probe the very first population of stars, population III (pop3) stars. While we expect only a fraction of pop3 stars would explode as PISNe, these explosions would be more observable than core collapse supernovae, especially at high redshift, making such explosions most likely the first observable signature of pop3 stars. While it is unlikely that we will be able to observe a convincing example of a pop3 star at a redshift of less than 6, we are quickly approaching that threshold and will need to know what to look for when the time comes.

Colin Jacobs - Using machine learning to search for strong gravitational lenses in astronomical 'Big Data'

My project, under Prof. Karl Glazebrook and computer vision expert Dr Chris McCarthy from the School of Software and Electrical Engineering, is investigating the application of modern machine learning techniques to astronomical data. As new telescopes and surveys such as DES, LSST and the SKA get up and running they will generate staggering amounts of data. Mining such large imaging databases for their scientific potential is a complex task that will require sophisticated automation. For instance, while we know of several hundred examples of strong gravitational lenses, tens of thousands are likely to be hiding amongst the data collected by these surveys. For my PhD project I am looking at the particular problem of teaching a computer to automatically identify galaxy-galaxy lens candidates using convolutional neural networks. If successful, astronomers will be able to use those lenses to probe the nature and distribution of dark matter and the shape and history of our universe.

Chandrashekar Murugeshan - Understanding Galaxy Evolution with Next Generation Radio Telescopes

Debatri Chattopadhyay -

Dany Vohl - GPU-Accelerated Discovery in the Petascale Astronomy Era

I will research, implement, test and evaluate new GPU-based approaches to
visualisation, data analysis and data intensive research with the goal of accelerating discovery in the Petascale Astronomy Era

Fabian Jankowski - The radio Universe at 1000 rames per second

I hold a degree "Diplom-Physiker" from DESY and Humboldt-University, Berlin, Germany. I specialise in experimental particle physics and further in astroparticle physics. My previous work was in gamma-ray astronomy. I focused on the question of the origin of cosmic rays, mostly from a theoretical point of view. I modelled the non-thermal multi-wavelength emission of supernova remnants from radio to TeV energies and compared this to broad-band observational data.

In September 2013 I commenced my PhD at Swinburne University of Technology under the supervision of Prof. Matthew Bailes and Dr. Willem van Straten. My interest is in pulsar science and radio transients. I am mainly involved in re-commissioning the Molonglo radio telescope. As a first step I investigated the population of pulsars and radio bursts that would be observable with Molonglo. Since then I have implemented an automatic observing mode, took data nearly every night, worked on pulsar timing, built an analysis pipeline for the incoherent mode and helped debugging the instrument. I am also involved in and lead observation proposals for the Parkes telescope.

For up-to-date information please visit my website.

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

Grace Lawrence -

Igor Andreoni - Super-Luminous Supernovae: Discovering the Deaths of the First Stars

My research interests include the detection and the science of transient events, along with 'multi-messenger' studies to search for electromagnetic counterparts to gravitational wave signals.

Transient sources appear in the sky, evolve, and finally fade away at all time-scales. Supernovae, for example, become bright (sometimes enough to rival the brightness of their own host galaxy) and then disappear within a few weeks, or a few months. However there are transient events that have very short durations that are relatively unexplored. For example, high-energy flashes called 'supernova shock breakouts' precede their optical emission (lasting only a few seconds), and mergers of neutron stars can produce explosions called 'kilonovae' (lasting only a few hours). Transients are therefore discovered over a wide range of time-scales and studied over the whole electromagnetic spectrum and beyond, as some catastrophic events emit a huge amount of energy in the form of gravitational waves. Gamma-ray bursts peak in the gamma rays, but their afterglow can be detected in the X-rays, ultraviolet, optical and at longer wavelengths, with some of them predicted to be gravitational waves sources. Finally, a new class of transients has been recently discovered in the radio called 'fast radio bursts'. These bursts last only a few milliseconds, less than a blink of your eye, but can be seen from across the Universe. Fast radio bursts, along with fast transients at all wavelengths, represent a challenging and unexplored world that we are now starting to unveil.

During my PhD I explore the fast (seconds to hours time-scale) dynamic Universe with coordinated, simultaneous observations in time-domain with radio, optical, UV, X-ray and gamma ray telescopes in the framework of the 'Deeper Wider Faster' project.

Isabel Rodriguez Herranz - Compact massive galaxy evolution, peanut-shaped bulges

James Esdaile -

Jacob Seiler - Reionization and Diffuse Cosmic Gas in the Universe

Understanding modern day structure depends critically on how well we can track the evolution of galaxies from small gravitational perturbations near the beginning of the Universe, through to the massive objects we currently observe. One important period in the evolution of the Universe is the Epoch of Reionization which marks the phase transition from a nearly homogenous Universe, to one that is highly structured. Probing this epoch presents an observational difficulty as the extreme distances prevents significant measurements from being made. My PhD will involve incorporating the physics behind the Epoch of Reionization into current models of galaxy formation. A further goal of my project will involve determining exactly how reionization proceeds; whether an 'inside-out' or more complex model model more accurately reproduces the observations we have.

Katharina Lutz - How do Galaxies Accrete Gas and Form Stars?

Galaxies host huge reservoirs of atomic hydrogen (HI). These HI clouds fuel smaller clouds of molecular hydrogen, which in turn form stars. When comparing the amount of gas that is transformed into stars with the total amount of gas available in galaxies, it is found that all available gas would be consumed within approximately 3 Billion years. This, however, is in contradiction to the average age of galaxies, which is approximately 10 Billion years. From that fact we can conclude that galaxies need to replenish their gas content to be able to keep on forming stars and by today it is common agreement that this is done via accretion. Nevertheless, the physical mechanisms behind accretion onto galaxies are not yet clear. In my PhD thesis I will observe the HI mass and velocity distribution of a sample of galaxies with exceptionally large HI content making use of the Australian Telescope Compact Array (ATCA) in order to search for clues of how accretion works.

Leonie Chevalier - The Study of Nearby Galaxies, their Evolutionary Histories and Dark Matter Content

Luz Angela Garcia - Intergalactic Metals at the conclusion of Reionization: theoretical

After the recombination epoch, all the Hydrogen in the Universe was neutral and the cosmic gas was filled of HI and other primordial elements. The hot plasma was essentially neutral and opaque (period commonly known as Dark Ages), but the formation and evolution of the first stars produced emission of ultraviolet photons, which ionized the Hydrogen, ending up with Reionization era. Despite the fact that the Universe was again transparent to be observed, the galaxy formation and enrichment of the ISM had proceeded, so there is a huge gap of the cosmic history that has been lost and must be studied by indirect observations in the sky.

One of best ways to study the early universe when Reionization occurred is using the QSO spectra. The Lyman absorption lines (and other metals) are the imprint of the absorbed incoming radiation from the quasar by the IGM and other structures.
QSOs are the brightest objects in the early Universe, therefore the study of their spectra is very important in Cosmology in order to understand the high redshift Universe.

In this scenario, the main goal of my research is to make theoretical predictions on how Reionization took place in the early Universe: was it an instantaneous (as a phase transition) or a continuous process? How did it happen? What was the topology of the the IGM sources during Reionization? The first question that the thesis will address is: how well is the fraction of neutral-to-ionized hydrogen represented by the fraction of low-to high ionisation metals? For instance, is there a tight relation of the fraction CII/CIV with HI/HII taking into account some physical conditions in the IGM?

Besides, the ionization potential of OI is similar to HI, hence, the ratio OI/OVI is expected to be a good proxy the neutral-to-ionized hydrogen ratio after Reionization?

These questions will be addressed by the use of hydrodynamical simulations with the SPH approach at redshift z~6 and will allow us to derive some constrains on the mass fraction of metals (OI, SiII, CIV, MgII, and FeII) with different ionizing UV backgrounds and compare the numerical results with observational measurements of metal absorption lines of QSOs spectrum.

Luca Rossi - The True Globular Cluster Mass Function Across the Hubble Sequence

Globular clusters are dense stellar systems that contain hundreds of thousands to millions of stars. They are found in large quantities in galaxies of all types. Indeed, they are the most ancient and best fossil records we have for probing the evolution history of galaxies. One important tool for such analysis is the globular cluster mass function (GCMF) of individual galaxies - essentially a census of the current globular cluster population of a galaxy. Complicating this census is that a globular cluster can be modified or even dissolved completely by the actions of the environment in which it resides - thus the present day GCMF will not reflect the true GCMF throughout the evolution history of the host galaxy. My PhD program aims to utilise numerical simulations of globular clusters evolving in a range of realistic galaxy environments to unearth the true GCMF as a function of host galaxy type.

The primary tool will be an N -body code called NBODY6 that is ideal for modelling globular cluster evolution in detail. Simulations with NBODY6 will be performed on the new Swinburne supercomputer (g2: gSTAR/swinSTAR) to take advantage of the speed-up offered by graphics processing unit (GPU) hardware.

Matt Agnew - A Dynamical Search for Habitable Worlds and Solar System Analogue

The search for exoplanets is now moving into a new era, where astronomers seek to quantify the number of Solar System analogues around other stars. Such a system will feature potentially habitable rocky planets like the Earth and massive Jupiter-like planets moving on decades-long orbits. But where should we look? How do we decide which exoplanetary systems are the most promising locations for potentially Earth-like planets? And which systems are most likely to host as-yet undetected Jupiter-like planets?

The core goal of my PhD is to use numerical techniques to search for dynamically stable planet candidates in the habitable zones of all known multiple planet systems.

Mark Durre - Active galactic nuclei: an examination of their physical environment and properties.

I am studying with Prof. Jeremy Mould, observing active galactic nuclei and their associated super-massive black holes, specifically looking at the dust and gas surrounding and obscuring the central engine.

Using near infrared integral field spectroscopy, the kinematics, distribution and other physical parameters of these features can be determined. We will use large telescopes with infra-red integral field spectroscopy with high spatial resolution, on samples of nearby radio source galaxies.

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 -

Renee Spiewak - Searches for Millisecond Pulsars and Fast Radio Bursts

PhD Candidate Searching for Millisecond Pulsars - with more to come

Sabine Bellstedt - Unveiling the Dark Halos of Eliptical Galaxies

Early-type galaxies (consisting of elliptical and lenticular galaxies) have in recent years been understood to display a large range of kinematic features, despite how homogeneous these galaxies appear from their imaging alone. We attribute these variances in kinematic features to be due to the varying formation histories that individual galaxies have, and through a combination of observational analysis and theoretical studies, we can now begin to identify what kind of formation history an individual galaxy may have undergone based on their observable features.

Most such studies have focussed on high-mass early-type galaxies. My work looks at the lower-mass early-type galaxies, to understand whether their formation scenarios mirror those of the higher mass galaxies, or whether there are different mechanisms at play. I also utilise kinematic mass modelling techniques to determine the total mass distribution within these galaxies, to understand how a galaxy's formation affects it's matter distribution (both stellar and dark), and to identify theoretically predicted trends observationally in the low-mass parameter space.

Stephanie Bernard -

Shivani Bhandari - The radio universe at 1,000 frames per second - instrumentation.Searching and Localisation of Sources of Dispersed Radio Emission

This project involves transforming Australia's largest radio telescope, Molonglo Radio Telescope, into wide-field camera capable of performing precision pulsar timing of multiple pulsars, radio sky mapping and searching the radio sky for fast radio bursts. The main goal is the commissioning of this large-scale project to achieve these cutting edge science goals.For this project, it will be necessary to cope with the hostile environment of Radio Astronomy.Main challenges involve detection and excision of radio frequency interference, phase the array to ultimately create tied array beams and radio maps using the output of the supercomputer. My science goals are related to the synthesis imaging using Molonglo, and also include the localisation of new pulsars that are being discovered at Parkes, large-scale structure in red-shifted HI.I am also part of the High Time Resolution Universe surveys (HITRUN) and Surveys for Pulsars and Extragalactic Radio Burst (SUPERB).

Sarah Hegarty - Accelerating and Enhancing Knowledge Discovery for the Petascale Astronomy Era

As astronomy enters a new era of petabyte-scale data, traditional approaches to visualisation and analysis will soon be inadequate for the astronomer's knowledge discovery needs. To address the need for new approaches, my PhD Project assesses traditional astronomical computing practices for the petascale age, and investigates the effectiveness of novel, emerging technologies for analysis and visualisation of large data sets.

Srdan Kotus - Do the fundamental constants of Nature vary in spacetime?

The main question in my work is whether the fundamental constants of nature are actually constant. Fundamental constants are numbers that are central to any physical theory, but those numbers cannot be calculated within those theories. We assume that these numbers are constants because, so far, we seem to find the same value whenever and wherever we try to measure them. The fine-structure constant is one of these numbers which characterizes the strength of electromagnetic force. There is currently some evidence that the fine-structure constant could vary in spacetime, which could be seen at very large distances.

In my PhD project we conduct an experiment in which we are looking at a cloud of gas between us and a background source of continuum light (quasar) through a spectrograph. When the light passes through gas clouds, only light at very specific colours (wavelengths) which corresponds to specific atoms/ions is absorbed. Through the spectrograph we see this as black stripes on a background rainbow. Among many things that we can infer from these stripes, we can see whether the distance between some of them is different compared to the same stripes measured in laboratory. If that is the case, which has been tentatively shown by my collaborators, than we can infer that the fine-structure constant in those clouds is slightly different from its value in the laboratory. Alternatively, we can check whether some systematic errors may be affecting the measurements.

My project is to look at new spectra taken from some of the largest optical telescopes in the world and see if there is some difference in fine-structure constant and also to search for systematic errors that can occur in these spectra.

Stephanie Pointon - Understanding the Relationship betwee Galaxies and their Gas

As much of half the baryonic mass of galaxies are found in galactic halos rather than stars and visible objects. This mass is in a gaseous form known as the circumgalactic medium. Currently, it is theorised that cold gas with low metallicity resupplies galaxies by spiralling in along the galactic plane. Galaxies, in turn, eject gas which has much higher metallicity and temperatures. Recent observations tend to support this theory. However, the theory has only been tested against a small number of galaxies.

The properties of the CGM are determined using the absorption lines found in quasar spectra. These absorption lines arise from the gas in the CGM absorbing the light from background quasars. Properties such as metallicity, temperature, column density and the kinematics can be calculated from the spectra. It is then possible to determine the behaviour of the CGM and the surrounding galaxies. Previous research has focused on lone galaxies. I will be expanding the survey of galaxies to include those in clusters.

Tim Dykes -

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.

Vincent Morello - Machine Learning for Radio-Astronomy

Vivek Venkatraman Krishnan - Advanced Software Correlation Techniques for Multi-Element Arrays

My PhD Thesis mainly focuses on developing new instrumentation techniques for time domain astronomy. I will specifically focus on new “Telescope Generic” ways to detect and excise radio frequency interference which is crucial at the dawn of the SKA era. I will also develop efficient algorithms for detection, analysis and timing of pulsars and other fast radio transients at real time harnessing the advancements in computer science such as massively parallel computing architectures and big data management. I will primarily use the Molonglo Observatory Synthesis Telescope (UTMOST) for my thesis which is currently being refurbished to have a new backend. Hence, I will be helping with several aspects of the refurbishment during the initial part of my PhD. Apart from UTMOST, I will also use the MEERKAT radio telescope and the CSIRO Parkes radio telescope for developing and testing my techniques. Once the techniques are developed, I will use them to do high precision pulsar timing and transient searching with the telescopes mentioned above.

Wael Farah - Machine Learning for Radio Transient Searches