Ph.D. projects at the Institute for Astronomy, University of Edinburgh

Updated: 7th Feb 2012.

Ph.D. Project proposals for September 2012 are now being added here in November and December. See the home pages of relevant staff, plus the research pages, for background detail. Potential Ph.D. applicants are advised to check back here from time-to-time.

We expect to take on approximately six new students. Most of these will be funded by STFC, which provide full funding only for UK students. However, the SUPA Prize studentships are unrestricted by nationality. See our funding information page for more details.

Links: Main IfA web page, and Main ROE web page (follow links to UK ATC for technology).

Please note that astronomy projects are also offered by the School of Mathematics, principally by Max Ruffert and Douglas Heggie, and in the Particle Physics Theory group elsewhere in the School of Physics and Astronomy, principally by Arjun Berera.

Important dates and Applications

Deadline for applications: Tuesday 31 January 2012. We may consider candidates after this date but do not guarantee to do so. To apply, return to the main IfA postgraduate page, or go directly to the Application page.

Deadline for SUPA applications: This has recently been extended to Friday 10 February 2012

Interviews: We will interview during February and March. The three currently planned interview dates are Tuesday 14th February 2012, Friday 2nd march, and Monday 5th March 2012.

Decisions: we expect to finalise our recruitment by the end of March.

Projects for September 2012 entry:

Supervisors: please follow template design below and add projects at the bottom.

The deepest ever images, and the cosmic evolution of the galaxy mass function

Supervisors: James Dunlop , Ross McLure

In summer 2012 we are co-leading a new 128-orbit Hubble Space Telescope project to take the deepest ever near-infrared image of the sky (in the Hubble Ultra Deep Field).

This project aims to exploit this unique new dataset, in combination with Hubble and Spitzer Space Telescope imaging already being obtained in this and other wider/shallower survey fields (e.g. the CANDELS Treasury project: http://candels.ucolick.org/) to establish the form and evolution of the galaxy stellar-mass function. The new deep HST/Spitzer data will enable this to be done over essentially all of cosmic time, and with enough dynamic range to provide a key test of alternative models of galaxy formation and evolution.

This PhD project offers the opportunity to work with the very best and latest near/mid-infrared data currently being obtained from space to establish a key observational benchmark for comparison with theory. The project is data led, but will require extensive computer modelling and simulation work to establish a robust and unbiased mass function. The project will also enable the student to get involved in collaborative work with different galaxy-evolution theory groups, who are eager to have a definitive mass-function measurement for testing and refinement of both semi-analytic and hydrodynamical models of galaxy formation.

Star-formation rates and masses for the most massive, high-redshift
galaxy clusters

Supervisors: Rob Ivison , Michele Cirasuolo

Galaxy clusters are the most massive gravitationally collapsed systems
in the Universe, and their mass and abundance at high redshift are
directly affected by the initial conditions of the Universe and the
early growth of density perturbations. This means that high-redshift
clusters are sensitive probes of non-Gaussianity in the initial
perturbation field and of the importance of Dark Energy at z >~ 1.
Clusters are the most biased and evolved environments at any given
epoch, and high-redshift clusters in particular provide important
astrophysical testbeds for galaxy evolution and formation.

Using guaranteed time with the Edinburgh-built KMOS spectrometer, on
the Very Large Telescope in Chile, this project will acquire data for
high-redshift, massive galaxy clusters selected via the
Sunyaev-Zel'dovich (SZ) effect from the South Pole Telescope (SPT)
survey, mostly at 0.9 < z < 1.0, but also for a handful of clusters at
z > 1.3. VLT/KMOS observations will provide spectroscopic redshifts
for the sample, velocity dispersions to improve the mass scaling and
cosmological parameter estimations, and spatially resolved H-alpha and
[O III] measurements of star formation and AGN activity in the richest
environments at z ~ 1. This project combines state-of-the-art
instrumentation with a unique sample of galaxy clusters and will
provide new insights into structure formation and evolution in rich
environments at high redshift.

The End of the Dark Ages

Supervisors: Avery Meiksin , Eric Tittley

After the hot gas from the Big Bang recombined, producing the Cosmic Microwave Background, the Universe was left dark. For some unknown
stretch of cosmic time, the Universe remained dark until the first stars and quasars formed. Efforts to discover these first sources of
light have provided an impetus to develop ever fainter optical and infra-red surveys and most recently a new class of large radio
telescopes like LOFAR and the Square Kilometre Array (SKA).

The purpose of this project is to make predictions for the detection of the first sources of light in the Universe by computing their
impact on the neutral intergalactic gas surrounding them. Two types of signals will be investigated, a radio 21cm signature from the gas and
a novel method, the detection of emission line halos, detectable in the infra-red. Using numerical simulations, the student will predict
the signals within the context of semi-analytic models for galaxy formation.

The student will be part of a group performing numerical computations in astrophysics at the Edinburgh Centre for Computation Astrophysics (ECCA). More information on the group is available at: ECCA.

Optimal Studies of the Dark Universe with 3D Lensing

Supervisors: Catherine Heymans, Tom Kitching, Alan Heavens

More than 95% of our Universe is Dark and unknown. One of the major goals in modern day Cosmology is to understand the Dark Universe and uncover the origin of the Dark Energy responsible for the accelerating expansion of the Universe. Weak gravitational lensing is a powerful technique that can map dark matter structures from its gravitational effects alone and probe dark energy through its effect on the growth of these structures. The IfA hosts one of the largest group of weak lensing researchers in the world with international collaborations with many of the world leading lensing surveys.

This Ph.D. project will develop, optimise and apply a full 3-D statistical weak lensing analysis to the state-of-the-art Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS). The student will focus on improving the accuracy of current 3D lensing methods by removing a potentially serious systematic error arising from an astrophysical intrinsic alignment effect that can mimic gravitational lensing. Once resolved, the student will be able to apply the method they have developed to the CFHTLenS to probe the evolving dark energy in our Universe.

This Ph.D. position is funded by the European Research Council and we welcome applications from all nationalities.

Mapping the chemical evolution of galaxies in the Local Volume with KMOS & the E-ELT

Supervisor: Chris Evans, Annette Ferguson

Chemical abundances in galaxies are typically determined using strong emission lines from HII regions, but these results are heavily dependent on the adopted calibration. A promising new method to probe chemical abundances in external galaxies is to use red supergiants (RSGs). These young, massive stars are extremely bright in the near-infrared. From analysis of absoprtion-line spectroscopy of RSGs in the J-band, we can map the star-forming history of their host galaxies directly.

This project will make use of Guaranteed Time with the new KMOS instrument, to obtain infrared spectroscopy of RSGs in galaxies at Mpc distances. Analysis of the observations with state-of-the-art model atmospheres will be used to obtain stellar metallicities and radial velocities, to give a 3D picture of the star-formation histories of these external galaixes, and to provide new constraints on the important relationship of stellar mass and metallicity. This project will also include simulations for future observations of RSGs with the European ELT. Infrared spectrographs such as HARMONI and EAGLE will open-up the hugely exciting prospect of direct chemical abundances of individual stars out to distances of tens of Mpc for the first time - a significant volume of the local Universe, containing entire galaxy clusters.

Development of Astronomical Instrumentation using Astrophotonics Technology

Supervisor: David Lee (e-mail david.lee@stfc.ac.uk)

The new field of astrophotonics aims to adapt photonics technology for use in astronomical instruments.Existing developments elsewhere include the use of fibre Bragg gratings to act as wavelength filters to remove atmospheric emission lines from astronomical spectra and the use of arrayed waveguides to disperse light. The United Kingdom Astronomy Technology Centre is currently working in collaboration with Heriot Watt University on the development of volume phase gratings manufactured in glass substrates using ultrafast laser inscription (ULI). These gratings are specifically aimed for use in near-infrared and mid-infrared instrumentation.

The student will work on the development of existing and new photonics technology for use in the next generation of astronomical instruments being designed by the UKATC. The student will design and test volume phase gratings which have been manufactured using ULI. The project will also involve the development of theoretical models of ULI grating behaviour. The student will also study the ULI manufacturing technique and optimise its performance for grating manufacture. The student will also investigate the synergies between waveguide technology and photonics technology with the aim of developing a slab waveguide spectrometer.

Design, development and characterisation of an affordable Real-Time Control System (RTCS) and micro-Deformable Mirror (µDM) for a multi-object instrument in the era of extremely large ground-based telescopes

Supervisors: Hermine Schnetler (e-mail hermine.schnetler@stfc.ac.uk) and Noah Schwartz

With the massive increase in the spatial resolution capability of the currently planned extremely large ground telescopes, the need for simple and affordable adaptive optics (AO) components will increase.The calibration and alignment of current AO systems are complex and time consuming and as such these systems are not easy to use and is also expensive to operate. The UK ATC was part of the EAGLE instrument and the advanced laser tomography system studies. EAGLE will be a multi-object instrument which will have the capability to perform 3-D spectral analysis simultaneously of twenty science fields distributed over a large patrol field. To achieve the required spatial resolution to deliver the science each instantaneous science field will be corrected for atmospheric turbulence by deploy

The student will work on the design, development and characterisation of the RTCS and the μDM. Firstly the student will be responsible for deriving the requirements for both items from the user requirements (science cases) and by working with the AO Systems Engineer at ONERA (Paris, France) utilising the existing analytical simulation model. Followed, the student will work with an engineering team composed of UK ATC and ONERA engineers to design, build and characterise (testing) the two major components in the laboratory. The student will also be responsible for the development of the test plan and defining the tests required to fully qualify the μDM and RTCS. There also might be an opportunity to test the component on-sky if the ONERA test facility is available. This will provide the student with an opportunity to compare the simulation results, with laboratory and on-sky results.

Characterising low luminosity stellar populations using PanSTARRS

Supervisors: Nigel Hambly, Annette Ferguson

PanSTARRS is a state-of-the-art sky survey project currently producing imaging data at an unprecedented rate in five optical passbands; the project has already imaged a significant fraction of the entire sky, and aims to revisit periodically each observed field to build up depth and/or time series measurements. It is the latter that makes PanSTARRS so important for studying low luminosity stellar populations, e.g. degenerate stars: the brown and white dwarfs. Such low luminosity stars are relatively nearby, and over time show significant motions against the backdrop of more distant objects. The nearest stars even show annual variations in their positions due to the changing line of sight as the Earth orbits the Sun (i.e. parallax). Because PanSTARRS will monitor the sky so deeply, it will discover tens of thousands of degenerate stars.

One suggested science topic to exploit the survey is to measure the ages of the Galactic thin and thick disks and spheroid via the white dwarf luminosity function. White dwarf cooling/fading can be modelled rather accurately, and since the three Galactic components have a finite age, there must be some absolute luminosity below which white dwarfs have not had time fade. Plotting the number of white dwarfs per luminosity bin (the white dwarf luminosity function) tells us about the star formation history of the Galaxy, and provides a means to measure population ages.

The very faintest radio sources and the evolution of galaxies and their black holes

Supervisors: Andy Lawrence, Rob Ivison

Radio emission is an excellent tracer of both star formation and nuclear activity in galaxies. The mixture of objects we see changes as we go to fainter0 radio fluxes. Bright radio sources are dominated by radio-loud quasars and radio galaxies, which have very strong radio jets. The majority of quasars, which are optically luminous but have much weaker radio emission, begin to show themselves at much fainter radio fluxes. However at these faint fluxes, starburst galaxies from moderately high redshift make up most of the counts. The standard models assume that star formation dominates faint radio emission, and that the number of very faint sources should start to tail off just below current observational limits. However, the faintest surveys attempted so far show flat counts that are hard to reconcile with these models, and the brightness of the radio background implies large numbers of very faint sources below current limits. One possible explanation is that much more star formation at high redshift took place in normal galaxies, as opposed to luminous starbursts, than has been previously thought. Another exciting possibility is that the black hole in every normal galaxy went through a radio-loud phase at high redshift.

These problems can now be tackled using recently upgraded astronomical facilities : eMERLIN, in the UK, and the EVLA in the USA, both of which are many times more sensitive than their old versions. We are part of a consortium making the deepest radio survey carried out to date, which also has high spatial resolution, which will enable us to distinguish galaxy size sources from nuclear activity. The first results should be arriving in mid-2012, with optical follow-up studies and even deeper surveys planned for later years. The student would help to produce the very first source counts in this new regime, analyse the morphological properties of sources, make IDs in associated deep multi-wavelength data sets, and compare to predictions of rival models.

Nuclear structures and gas flow in active galaxies

Supervisor: Andy Lawrence

The quasar phenomenon is believed to be caused by accretion of matter onto supermassive black holes in the nuclei of galaxies. Conversely, it is believed that feedback from early quasar outflows is crucial to the process of galaxy formation. However, the gas flow in the nuclear regions is both theoretically and observationally contentious. For example the black hole spin axis seems to be randomly oriented with respect to the parent galaxy, and just outside the accretion disc itself, there seems to be a geometrically thick obscuring structure radiating in the infra-red, which rival models claim is either a warped disk or a doughnut-shaped region of orbiting dust clouds. New facilities give us greatly improved opportunity to resolve inner structures at sub-arcsec scale : deep radio maps will tell us the true black hole axis, and molecular observations with ALMA will show us the structure and motion of the incoming cold material. Improved IR data and spectroscopy will enable us to model the "dusty torus" region which sits between the incoming material and the inner accretion disk.

The student would begin with reduction and analysis of existing IR data and optical spectra. By the time the project starts, we hope to have the first observations of radio jets and molecular disks.

The SCUBA-2 Unbiased Nearby Stars Survey

Supervisor: Wayne Holland (wayne.holland@stfc.ac.uk)

Debris disks are the detritus of comet collisions and their presence around nearby stars is strong evidence that planets also exist in these systems. They provide a unique way to study how planetary systems form and evolve from their primordial structures. Observations tell us about the scale of regions with planetesimals, locations of perturbing planets and the evolution of the comet population that can affect terrestrial planet habitability. Major scientific goals over the next few years range from searching for analogs of our Kuiper Belt to assess whether the Solar System configuration is unique, providing higher resolution images of the disk structures to better constrain the positions of perturbing planets, and to study the physical and chemical properties of the disk material.

The SCUBA-2 Unbiased Nearby Stars survey (SUNS) will carry out an imaging survey of 500 nearby main-sequence stars, 100 of each in the A, F, G, K and M spectral types, searching for debris signatures at a wavelength of 850µm. Holland is one of the principal investigators for SUNS, which started in the Autumn of 2011. The project will be largely observationally based, using SCUBA-2 on the James Clerk Maxwell telescope in Hawaii and also potentially other facilities. The student will be expected to lead a substantial part of the data reduction and interpretation.

Using numerical simulations to identify self-gravitating protostellar discs

Supervisor: Ken Rice

There is increasing evidence that discs around very young stars can be massive relative to the mass of the central object. In such systems, the disc self-gravity becomes important and can lead to the growth of a gravitational instability. This instability is likely to play a crucial role in the transport of angular momentum outwards, allowing mass to accrete onto the central star. It may also play an important role in the growth of planet building material, and there is increasing evidence suggesting that the building blocks of planets must indeed form during the earliest stages of star formation. Understanding the formation and evolution of self-gravitating discs around young stars is therefore an extremely important part of understanding fundamental aspects of star and planet formation.

We have carried out numerous numerical simulations to investigate the evolution of self-gravitating discs. What we have not investigated in great detail is how to identify these self-gravitating discs around young stars. Current surveys are likely to identify numerous very young stellar objects and, in the near future, we are likely to be able to investigate such systems in detail. The goal of this project will therefore be to extract observational signatures of self-gravitating discs using existing numerical simulation data and using newly generated simulation data. We want to take advantage of new high-performance computing that has recently become available and so part of the project will involve becoming familiar with a new numerical code (SEREN) that is optimised for these new high-performance systems. A radiation transfer code for determining observational characteristics of the simulated discs does already exist but will need some additional development. In particular, it will need testing, optimisation and, ideally, modification to run on multi-processor systems. We have a local cluster and have access to other high-performance computing systems.

Computational Radiative Transfer

Supervisors: Avery Meiksin, Eric Tittley

Cosmological simulations of structure formation have shown that radiative processes play a vital role in the structure of the intergalactic medium (IGM) and the formation of galaxies. The first sources of ultra-violet radiation like young hot stars and quasars reionize and heat the IGM, expel gas from the first collapsing dark matter haloes, dissociate molecular hydrogen and may establish a feedback mechanism that regulates galaxy formation. Further progress in understanding cosmological structure formation requires incorporating these processes into the codes.

While combined gravity-hydrodynamics codes are well-developed, radiative transport requires a separate treatment. In the limits of optically thick and thin conditions, approximations can be made that permit a simple implementation. In the intermediate case of mixed opacity, ray-tracing is required. Binding a general radiative transfer code with a gas dynamics code is not trivial: the ray of radiation travels through many gas elements, each of which removes some of the energy as the light travels.

The proposed PhD project is to implement a generalized ray-tracing or similar algorithm to bind radiative transport to either a grid-based code or a Smoothed Particle Hydrodynamics code like Gadget, widely used in the simulation community. It is expected that the algorithm would be ready for the future state-of-the-art high performance
computing platforms. Parallelization to work on Generalized Computing Graphics Processing Units GC-GPUs is essential, since future HPC performance will be driven by the extreme threading provided currently by GPUs.

The student will be part of a group performing numerical computations in astrophysics at the Edinburgh Centre for Computation Astrophysics (ECCA). More information on the group is available at: ECCA.

Disentangling the Clustering and Geometric Effects in 3-D Weak Lensing

Supervisors: Andy Taylor, Tom Kitching

Weak gravitational lensing distorts the images of distant galaxies due to the deflection of light by foreground structure. Combined with distances, in 3-D Weak Lensing, this signal can be used to directly probe the clustered matter in the Universe, and its geometry. This in turn can be used to probe both dark matter, dark energy and any modification to gravity on large-scales. The IfA at Edinburgh hosts the world largest group working on Weak Lensing and leads most of the worlds major weak lensing surveys.

This PhD project is to develop and apply a new method to disentangle the clustering and geometric effects from 3-D Weak Lensing. This will allow us to directly measure the dark matter and baryon clustering pattern to compare with theoretical models, and a geometric signal which can measure cosmology independently of the clustering model. The former will improve our understanding of dark matter and the role of baryons, while the latter will boost the available data for measuring dark energy and modified gravity. These methods will be applied to the CFHTLens survey, the largest weak lensing survey in the world. In parallel, the student will develop and run simulations of weak lensing to test the disentanglement methods and understand its biases and uncertainties. These methods and simulations will also be used to aid the development of future dark matter missions such as ESA's Euclid satellite mission.

Measuring the masses of galaxy clusters

Supervisors: Bob Mann, Catherine Heymans

Galaxy clusters are the most massive gravitationally bound systems in the Universe, which makes their abundance and its evolution with redshift a powerful probe of cosmology. In practice, their use in this role has been limited by difficulties in measuring the masses of sufficiently large cluster samples. Clusters are most readily detected in sky surveys undertaken in the X-ray and (via the Sunyaev-Zeldovich effect) in the millimetre bands, but neither type of observation yields a direct mass estimate, nor does the simplest analysis of imaging surveys in the optical or near-infrared. All these observations generate only estimates for mass proxies, whose relations to the true gravitational mass of the cluster may be subject to systematic errors, and which, at the very least, require calibration.

One technique, namely weak gravitational lensing, does directly probe the gravitational mass of a cluster, but current lensing data struggles to measure the masses for many individual clusters, so one must resort to using lensing data to perform statistical calibrations of the cluster mass proxies more readily measured in other data if one wants to determine the masses of large samples of clusters.

The goal of this project is to do just that, through combination of X-ray data from the XMM Cluster Survey (XCS) and SZ data from the Planck satellite soon to be made public, together with weak lensing and cluster richness data to be obtained from the Pan-STARRS optical sky survey, to produce the best calibration yet of cluster mass proxies and to exploit the accurate cluster masses that will result for cosmology and cluster astrophysics.

Regularising the galaxy density field to probe primordial cosmology

Supervisors: Sylvain de la Torre, John Peacock

The mass density field as traced by galaxies provides fundamental information about the universal expansion history and growth of structure. In particular, the variance of the density field is a very powerful tool for understanding the Dark Universe and probing gravity on cosmological scales. The non-linear evolution of mass density perturbations however complicates its direct interpretation. A novel approach to reduce the impact of non-linearities consists in regularising the density field by under-weighting the objects in strongly non-linear structures.

The aim of this project is to develop and optimise new estimators of the power spectrum in real- and redshift-space where most of the non-linearities have been erased, therefore facilitating the modelling and possibly diminishing the uncertainties on the recovered cosmological parameters. This project involves working with large numerical simulations as well as with observational data from a large spectroscopic survey. The final goal is to apply the newly developed techniques to the VIPERS redshift survey and put tight constraints on the cosmological parameters from the observed real- and redshift-space clustering.