Potential PhD Topics

The following list of PhD projects is currently available at the Centre. Please contact the staff member listed for more information.

Dynamics of Rich Galaxy Clusters

Probing Galaxy Groups and Measuring the Invisible

Evolution of Galaxy Morphology

Evolution of Star Clusters

First Light

From Dust to Planets

Galactic Novae Populations Across the Ages

Keck Spectra of Globular Clusters

Protosteller Disk Dynamics

Relativistic Binary Pulsars

Testing Formation models in the extreme - The Shapley Supercluster

The AAOmega WiggleZ Survey: measuring dark energy and galaxy evolution at half the Hubble time

The Galaxy Mass-Metalicity relation at high-redshift

Supermassive Black Holes

Alignment of Galaxies in the Cosmic Web

Cosmological Simulations of Future Radio Surveys

Do the constants of Nature vary in spacetime?

Laser frequency combs: a new standard for astronomical spectra

Galaxies revealed by quasar absorption lines

The baryon and gas budgets for the Universe

Most galaxies are found in groups, yet they are poorly studied relative to clusters. Using wide field spectrographs (eg AAOmega on the AAT and DEIMOS on the Keck Telescope) we can obtain stellar population properties and kinematics for a large sample of group galaxies. This will allow us to create a new volume and magnitude complete census of group galaxies. We aim to identify the mechanism for pre-processing in groups and to measure the dark matter halo mass from the kinematics of group dwarf galaxies and globular clusters. Isolated galaxies and fossil groups will form an interesting control sample. This observational project involves collaborators in the UK and California. Supervisor Prof. Duncan Forbes

Perhaps the key problem in globular cluster research today is understanding the origin of the two subpopulations. Although much has been learnt from imaging, progress on this issue requires information that can only be gained from spectroscopy. Spectra give metallicity, abundance, age and kinematic properties. Such properties can be used to distinguish between the competing globular cluster formation models. We have excellent access to the world's largest telescope (Keck) which is necessary to obtain the required spectra. This project involves collaborators in California. Supervisor Prof. Duncan Forbes

Supercomputer power has now risen to the point where it is possible to search recent surveys for relativistic binary pulsars using acceleration codes. Swinburne has one of the most powerful supercomputers in the world - the combined power of the Swinburne and Parkes machines is almost 16 Teraflops. This is one of most powerful supercomputers in the world that is dedicated to astronomy. A project is available to search the recent Parkes and Swinburne surveys for relativistic pulsars on the supercomputer, and use the Centre's advanced 3D visualisation laboratory to analyse the results. New data from a new digital survey will come online in 2008 that will enable astronomers to search the galactic plane in unprecedented detail for millisecond pulsars. Sophisticated modelling codes for the population will enable the opportunity for both theory and observation. Supervisors: Prof. Matthew Bailes, Dr Willem van Straten , Dr David Barnes.

With over one hundred newly discovered extra-solar planets, it is becoming very important to study the planet formation process. These new solar systems are so clearly different from our own that we have to totally revise our ideas of how planets come to be. There is an ongoing project at Swinburne to study the earliest stages of the process in which micron size dust particles aggregate together to form metre size boulders that form the base material for planets. The PhD student will work on both theoretical and observational aspects of the problem. Theoryside, the student will use and modify our dusty gas modelling code, and run it on the Swinburne supercomputer. Infrared and radio observations will complement the numerical results. Sarah is currently collaborating with groups in France, England and the USA on this project and the new student will become involved with these collaborations. Supervisor Dr. Sarah Maddison

The Stars & Planets group are involved in a variety of projects studying the dynamics of disks around young stars - including protostellar, circumbinary and protoplanetary disks. The PhD student will work on both theoretical and observational aspects of the problem. The student will use and modify our hydrodynamics code and run simulations on the Swinburne supercomputer. Infrared and radio observations will complement the numerical results. Sarah is currently collaborating with groups in France and Germany on this project and the new student will become involved with these collaborations. Supervisor Dr. Sarah Maddison

The 2dF Galaxy Redshift Survey and 6dF Galaxy Survey provide unique redshift data for rich clusters. Large numbers of redshifts enable the dynamical state of clusters to be determined accurately. The PhD student would investigate 1) the frequency and magnitude of peculiar velocities of Brightest Cluster Galaxies (BCGs) - as a guide to the dynamical state of the cluster, and 2) substructure (spatially and kinematically) by studying rich clusters with large numbers of galaxy redshifts. BCGs have previously thought to be located at the spatial and kinematical centre of rich clusters - recent results suggest that 30\% of all clusters have BCGs with significant peculiar velocities (BCG - cluster mean) suggesting that many nearby clusters are still dynamically young and evolving. Substructure can be identified optically (via redshifts and positions) and via the structure of hot gas (X-ray imaging). Quantifying substructure can reveal clues to the initial density perturbations out of which large scale structure (clusters, groups) form. Supervisor Dr. Glen Mackie

The Shapley Supercluster (SSC) is the most massive concentration of galaxies in the local universe. Recent redshift surveys have elucidated the distribution of bright galaxies in the core and outskirts of the SSC. The close vicinity of the SSC and it's large overdensity of galaxies offers a unique perspective into galaxy evolution at the very extreme of space densities. In general star formation appears to be quenched or supressed for recently accreted galaxies. The PhD student would try to answer many remaining questions concerning the linkages between galaxy evolution and cluster environment. eg. Does the initial impact with the hot intracluster medium (ICM) cause an initial starburst then rather abrupt star formation cessation? Current observational plans include deep imaging of the SSC to explore the evolutionary status of low luminosity galaxies in conjunction with 6dF Galaxy Survey redshifts, the structure of the hot X-ray emitting gas and expanding on previous radio continuum studies. Current hierarchical models predict clear trends for elliptical galaxies in such environments and we intend to extend current observational vs. theoretical comparisons to below L* galaxies. Supervisor Dr. Glen Mackie

Understanding the nature of the apparent 'dark energy' that is causing the expansion of the universe to accelerate, and establishing the physical processes by which galaxies assemble and evolve into the well structured systems we see today, represent perhaps the two most important challenges to modern observational cosmology. In collaboration with colleagues at the University of Queensland, the Anglo-Australian Observatory, Johns Hopkins University, and the University of British Columbia, we plan to undertake what will be the largest ever redshift survey of the distant universe, which will allow us to simultaneously address these two important problems.

Using the new and innovative AAOmega wide-field multi-object spectrograph on the 3.9m Anglo-Australian Telescope (AAT), we will obtain redshifts for more than 500,000 emission-line galaxies, pre-selected using the 'Lyman-Break' method to be at a redshift of z ~ 1. This enormous sample of galaxies, along with the very large cosmic volume that it will be drawn from, will allow is to measure very accurately and precisely the clustering of galaxies at this earlier epoch. Such information should reveal the "baryonic acoustic oscillations" signature imprinted upon the galaxy distribution soon after the Big Bang, which provides an ideal 'standard ruler' for measuring the dark energy equation of state.

This large survey has a number of exciting possibilities in terms of providing PhD projects, working in either the area of dark energy or galaxy evolution. These would be observationally-intensive projects, involving numerous trips to the AAT at Siding Spring Observatory in northern NSW, and working within a large team. They would also require the student to have good computational and analytical skills. There would also be a strong emphasis on the student traveling internationally to attend major cosmology meetings and publicise the survey and its results.

Supervisors Prof. Warrick Couch, Prof. Duncan Forbes, Prof. Karl Glazebrook & Dr. Chris Blake

The relationship between a galaxies stellar mass and metallicity has emerged as a key test of galaxy evolution scenarios. For example Baldry, Glazebrook & Driver (2008) (BGD2008) have used this to calculate the baryonic mass function of galaxies (stars + invisible gas) in the Sloan survey (SDSS).

The PhD project is to measure galaxy gas metallicities for hi and especially **low**-mass objects at high-redshift, using classical emission line ratios. (R23, O3N2). This will require NIR spectroscopy and is made possible by the new multi-slit NIR spectrographs being commissioned in 2008-2009, especially the new MOSFIRE instrument for Keck. A very good z=1 sample is from ROLES - an [OII] selected K_AB < 24 sample from Magellan optical spectroscopy probing down to low-mass dwarf galaxies. The 'Gemini Deep Deep Survey' will also provide targets up to z=2. This has not been done at z > 0.7 for individual galaxies (composite spectra only have been used to do this at z > 2 (Erb et al. 2006) due to the limitations of single slit NIR spectrographs).

The mass-metallicity-redshift relation derived will be used to test semi-analytic models of galaxy formation, but will also be used to construct semi-empirical models of galaxy formation following the BGD2008 technique. An important component will be testing the assumptions of the method. Another interesting spin-off will be deriving predictions for HI (i.e. neutral hydrogen) mass functions both at low-z and high-z, this will be very relevant to SKA and is an entirely new method of predicting HI at high-z using purely optical/IR data. Supervisors Prof. Karl Glazebrook & Dr. Michael Murphy

Deep imaging surveys combining HST imaging and ground space spectroscopy are painting a picture of galaxy morphological evolution - the origin of the Hubble sequence - at redshifts 1 < z < 2. We are seeing strong evolution in the properties of elliptical and spiral galaxies, not of all which can be easily explained.

The 'Gemini Deep Deep Survey' is a stellar-mass selected sample of galaxies at these redshifts complete with imaging from HST (ACS and NICMOS) and Spitzer already taken. These images are of high-enough resolution to provide accurate morphological discrimination of spirals and ellipticals and have already revealed some surprises: strong evolution in the space density of elliptical galaxies (Abraham et al. 2007) and the Kormendy relation (Dajmanov et al. 2008). The latter has revealed a population of super-compact massive elliptical galaxies at z=1.6 ('red nuggets') which are absent in the local Universe and can not be explained in current models.

The PhD project is to analyze the existing data - looking at the evolution of spirals, determining the effect of environment on spirals and ellipticals, take some new data with Keck to greatly improve knowledge and statistics and perhaps solve the mystery of the red nuggets. Supervisor Prof. Karl Glazebrook

A key problem in cosmology is finding the epoch in time when the first structures in the Universe collapsed to form the first stars. The UV from these stars ionized the neutral hydrogen in the universe left over from the Big Bang, a process called 'reionization'. Current observations have pushed this epoch back to z > 7.

Accessing this epoch required deep NIR observations because all the emission from candidate objects is redshifted out of the optical region. Such observations are difficult because of the bright airglow from the night sky at these wavelengths. At Swinburne we are developing a new technology photonic filter which if successful could suppress this emission and make existing telescopes 10-20x more sensitive. Another technological advance is the advent of MCAO (Multi-Conjugate Adaptive Optics) which could allow for deep NIR imaging over wide fields with a spatial resolution better than HST.

Part of this PhD project will be to work on the design, development and testing of this filter. The other part will be to carry out deep near-IR observations (possibly using this filter) to detect galaxy poplulations beyond z > 7 using the classical 'Lyman Break technique'. Supervisors Prof. Karl Glazebrook & Dr. Paul Stoddart (Applied Optics)

Cataclysmic variables (CVs) are binary stars in which the cannibalistic accretion of hydrogen-rich material from a red dwarf companion onto a white dwarf (WD) leads to periodic eruptions on the WD surface known as novae. These outbursts are incredibly energetic and make novae visible in galaxies outside of our own. Currently there is a significant and, so far, unsettled debate in the literature concerning the correlation between nova rate and Hubble type of galaxy. Traditionally it was thought that brighter, faster novae, powered by massive WDs, should more frequently appear in spiral galaxies (with young populations). Conversely, elliptical galaxies (with little or no recent star formation) are not expected to exhibit many luminous novae because the CV population will be dominated by low-mass WDs with low surface gravities. However, recent observations of many bright novae in the old elliptical galaxy M87 contradicts this point of view.

The goal of this project is to provide a more realistic set of nova population models than has hitherto been produced and to do this for a range of galaxy types. The PhD student would be responsible for interfacing the latest detailed models of nova outbursts (provided by collaborators at Tel Aviv University) with a binary evolution code. The student would then use this code to create artificial CV/novae populations for all galaxy types, `observe' these populations and make a detailed comparison with the M87 (and future) observations. Supervisor Dr. Jarrod Hurley.

Here at Swinburne we have a range of N-body codes that model all facets of star cluster evolution. We also have teraflops computing power at our disposal via the Swinburne supercomputer and access to GRAPE-6 machines. This software and hardware combination means we can produce direct and realistic models of star clusters. Further hardware advances in 2007/08 will allow direct modelling of Galactic globular clusters for the first time. As such this is a very exciting time for the field of star cluster simulation and a variety of associated projects are available. These include: the destruction of open clusters in our Galaxy; the formation of exotic stars via dynamical interactions in star clusters; the morphology of planetary systems in star clusters; stellar nucleosynthesis feedback in star clusters; the effect of dynamical evolution on the appearance of globular clusters; and intermediate-mass black holes in globular clusters. Plus numerous other possibilities - please get in touch if you have an idea not listed here. Supervisor Dr. Jarrod Hurley.

It has recently been recognised that "supermassive black holes", with masses one million to one billion times more massive than our Sun, reside at the heart of most galaxies (even those without an `active galactic nucleus'). Curiously, they appear to consistently represent 0.1 percent of the host galaxy's mass. Better understanding the connection between a galaxy's global stellar distribution and its central stellar density is expected to yield valuable insights into this phenomenon. This can be achieved through the careful analysis of Hubble Space Telescope images at optical and near-infrared wavelengths. Moreover, such high-resolution images actually allow one to measure the galactic damage caused by these cosmic wrecking balls. Supervisor Dr Alister Graham.

The constants of Nature play a central role in our fundamental physical theories but these theories cannot predict the values of the constants we observe. Indeed, this is one hint that our theories may be incomplete and that a more fundamental, "grand unified theory" linking all physical interactions -- gravitational, electromagnetic and nuclear - might exist. Perhaps surprisingly, the absorption lines seen in the spectra of extremely distant quasars offer a fairly clean and precise probe of the values of some fundamental constants early in the Universe's history. Over the past 7 years, I have uncovered tentative -- and tantalising -- evidence that some constants may actually vary on 10 billion year time-scales. This PhD project aims to use new and existing quasar spectra to confirm or refute this evidence. Many different avenues may be followed in this project, but most are observational in nature with an emphasis on careful and repeatable data analysis. The student would carry out new observations on the world's largest telescopes (mostly the Very Large Telescope in Chile and Keck in Hawaii) and would analyse a large database of existing quasar spectra. There is also opportunity to use radio absorption spectra for similar studies. The student would collaborate with researchers in Sydney and in Cambridge (UK). Supervisor Dr Michael Murphy.

The 2005 Nobel Prize in Physics was awarded for the invention and application of the new laser frequency comb (LFC) technology. As the name suggests, LFCs provide a series of equally spaced "emission lines" which cover a very broad range of wavelengths. I am working with the European Southern Observatory (ESO) on building a LFC system that might be used to provide an ultra-precise wavelength standard for spectrographs on the Very Large Telescope in Chile and even on the planned European Extremely Large Telescope. But to understand how precisely we can really calibrate a spectrograph, sophisticated models must be constructed which allow us to simulate LFC spectra and how they are recorded with digital detectors like CCDs. This project mainly involes computational modelling and data analysis but it may also involve testing a LFC at the Anglo Australian Telescope in collaboration with the Centre for Atom Optics and Ultrafast Spectroscopy at Swinburne. The student would also collaborate with ESO to produce computer models of their planned LFC system, an effort which has just begun in Trieste (Italy). Supervisor Dr Michael Murphy.

As the light from distant quasars travels through the Universe on its way to Earth, it occasionally passes through the outskirts of a galaxy. By identifying the absorption lines in quasar spectra that they cause, we can detect galaxies which may otherwise be too distant and faint to see with direct imaging. This is a potentially huge advantage of so-called "absorption selection". But there's a catch: the link between the absorption line properties and the galaxy properties is still unclear and so we must first study a sample of absorption-selected galaxies which are not so faint and distant as to be directly imaged to establish this relationship. Unfortunately, it's difficult to see even bright galaxies in the glare of the background quasars and most attempts at this have failed. However, with the Very Large Telescope in Chile (VLT) we have recently studied some details of some special classes of absorption-selected galaxies. We now aim to obtain Hubble Space Telescope observations to further characterise these galaxies. Large, ground-based telescopes like the VLT and Keck (Hawaii) will also be used to find more distant, and possibly more representative, galaxies. This project is observational in nature. There is opportunity for collaboration with groups based in Cambridge (UK), California (USA) and Victoria (Canada). Supervisor Dr Michael Murphy.

As the Universe evolves, gas is turned into stars and then, when the stars explode, the baryons are liberated into gas again. But through this recycling of interstellar material, we expect that the amount of neutral hydrogen available for star-formation should decrease as the Universe evolves. Tracking this depletion of neutral gas is one of the fundamental observational pointers for theories of galaxy formation. Most of the neutral gas in the early Universe resided in so-called "damped Lyman-alpha" systems (DLAs) -- gas clouds identified in quasar spectra by their strong (damped) neutral hydrogen Lyman-alpha absorption line. But now most gas resides in stars and, assuming that DLAs really do trace the formation of stars, it is hypothesised that the number and hydrogen content of DLAs should therefore have decreased over the past 5 billion years. This PhD project aims to find evidence of this: if it's found then it will help constrain theories of galaxy formation; if it isn't found then it will profoundly impact our understanding of the link between DLAs and star formation throughout the Universe. This is an observational project: we have begun an extensive survey for DLAs aimed at finding evidence for evolution in the DLA population. Observing time on the Shane 3-m telescope at Lick Observatory (California) is already secured and we are seeking time on larger telescopes like the 4-m William Herschel Telescope (La Palma, Spain), the Multiple Mirror Telescope (Arizona) and 10-m Keck Telescope (Hawaii). This is part of a collaboration with researchers in the UK and USA. Supervisor Dr Michael Murphy.