Edinburgh PhD Projects 2006

The following is a brief list of PhD Project proposals for September 2006. See the home pages of relevant staff, plus the research pages, for background detail. It is still under construction, and projects will probably continue to be added until February 2006.

We expect to take on approximately six new students. Most of these will be funded by PPARC and hence restricted to UK students. However, the SUPA Prize studentships are unrestricted by nationality. Also, there is a studentship open to any EU student to work on Stellar Populations and Galaxy Formation. See our funding information page for more details.

All PhD places for 2006 are now allocated, so this list is now mainly to indicate the sort of projects that are given to research students in Edinburgh.

Title: The SCUBA2 Cosmology Legacy Survey

Supervisor: James Dunlop

In recent years the advent of the world's first sub-mm camera, SCUBA, has revolutionized our picture of the young universe. SCUBA, built here in Edinburgh, and mounted on the James Clerk Maxwell Telescope (JCMT) in Hawaii, has revealed the existence of a significant population of dust-enshrouded starburst galaxies at high redshift. These galaxies appear to be in the process of forming thousands of stars per year. However, because this violent star-formation activity is enshrouded by dust (itself made by short-lived massive stars) the ultraviolet light from the young stars is absorbed and re-emitted in the far-infrared, and then redshifted to sub-mm wavelengths. As a result, these objects are most readily (in some cases only) detectable with a sub-mm telescope/camera.

The discovery of these objects has opened up what is essentially a new field of sub-mm cosmology. Edinburgh astronomers have been in the vanguard of this work, and we have led a number of major studies designed to establish the prevalence, and nature of these important objects. However, many key questions presently remain unanswered. In particular it is not clear what role these objects play in the overall formation and evolution of todays population of galaxies. This is a particularly important question to answer because current theoretical models of galaxy formation struggle to reproduce the observed population of high-redshift submm-selected galaxies without somewhat ad hoc modifications.

To answer this question requires the detailed multi-frequency study of well-defined samples of several thousand submm-selected galaxies. To date this has not been possible, simply because SCUBA, like all first-generation instruments, is relatively crude (e.g. it only has 3 dozen pixels). However, this situation is about to be transformed with the advent of SCUBA2. This revolutionary instrument, the world's first `CCD-style' submm camera (with several thousand pixels) is currently being completed here in Edinburgh, and is due to commence operation in Hawaii in early 2007. To fully exploit the unique power of this new instrument, James Dunlop at Edinburgh is co-leading a major international survey - the SCUBA2 Cosmology Legacy Survey - designed to commence data taking in mid 2007.

The time is therefore now appropriate for a new PhD student to join this survey team in Edinburgh, to contribute to the design and implementation of this major new submm project. The project is broad enough that there will be considerable scope for the new post-grad student to define the scientific focus of their project. However, at least initially, we anticipate that the new student will begin by becoming closely involved with refining the final design of the survey, and will play a key role in and early data taking and analysis in Hawaii.

Title: Aeronomy of hot giant exo-planets

Supervisor: Wing-Fai Thi

Possible co-supervisor: Christiane Helling

Among the exoplanets detected so far, the close-in extrasolar giants planets (aka hot Jupiters) are of particular interest since they have a more active chemical process in their upper atmospheres and the evolution of their atmospheres can be studied observationally. Recent observations by HST of atomic hydrogen absorption in the Lyman-alpha line indicate that the upper atmosphere of the short-period giant planet HD209458b is extended up to about 3 planetary radii. Current and future observations of heavy atmospheric species such as C, N, O, S, Si and Fe beyond the Roche lobe can be seen as a confirmation that the giant experiences X-ray-UV-driven hydrodynamic conditions where a planetary thermal wind carries the heavier species away from the planet. This project will investigate theoretically the photochemical and hydrodynamical processes that occur in the upper atmosphere of exoplanets irradiated by the parent star. The goal is to study the evolution of the upper atmosphere (exosphere), its composition and structure as well as to determine possible line tracers, which would be detectable with future instruments.

Title: Stellar Populations and Galaxy Formation

Supervisor: Annette Ferguson

The IfA hosts a newly-formed research group led by Annette Ferguson, which is focused on studying resolved stellar populations in the Local Universe as a probe of galaxy formation and evolution. The thesis project in this group is of an observational nature and will primarily involve the analysis of wide-field ground-based observations (obtained with the VLT, Subaru and UKIRT) for sample of nearby galaxies. This project is funded separately by a Marie Curie Excellence Grant from the European Commission.

Title: Testing models of galaxy and AGN evolution

Supervisors: R. Ivison, A. Biggs

SCUBA resolved uncovered a population of star-forming, dusty galaxies which dominate the energy budget in the early Universe. An order of magnitude larger than its predecessors, the SHADES survey is providing a sample of submm galaxies from two large, contiguous regions of sky, aiming to: 1) measure the history of dust-enshrouded star formation; 2) measure the scale length of galaxy clustering; 3) determine the fraction of sources that harbour active galactic nuclei (AGN). This project will begin by using the Giant Metre-wave Radio Telescope (GMRT) to determine the radio spectral indices of radio-faint (but hyperluminous) starbursts. The GMRT data will probe radio-loud AGN, and ensure that appropriate SED templates are employed to estimate photometric redshifts, thereby playing a significant role in all three of the SHADES science themes.

Title: The IMF in distant, obscured galaxies

Supervisor: Chris Evans

One of the largest uncertainties in the interpretation of distant, obscured starbursts remains the initial distribution of stellar masses, the so-called initial mass function; the physical processes of how the most massive stars are formed are still relatively poorly understood. With new multi-fibre VLT observations we have obtained an unprecedented optical survey of the stellar content of the largest cluster in the Small Magellanic Cloud. Combined with new HST-ACS imaging, this project will look at the star-formation history and the initial mass function in this young region.

Title: Luminous A-type supergiants - a powerful new method of determining distances

Supervisor: Chris Evans

Recent advances in stellar astrophysics have yielded a powerful new method (FGLR - Flux-Weighted Gravity-Luminosity Relationship) of determining distances, useful well beyond the Local Group of galaxies with existing telescopes and instrumentation. Initial observational tests have shown the relationship to be fairly robust, but further calibration in different environments is essential to demonstrate the validity of the method. New VLT observations of the most visually luminous stars at the edge of the Local Group will be combined with theoretical model atmosphere techniques to better calibrate this method in the local Universe.

Title: Gas in young planet-forming disks

Supervisors: Susanne Ramsay Howat, Bill Dent

The gas content of the inner few AU of young proto-planetary discs has a significant effect on the formation of giant planets such as Jupiter. But this gas is difficult to measure. Initial results in small numbers of well studied sources have produced controversial estimates of the mass and physical conditions of this gas. This project will select a well-defined sample of discs based on their geometrical properties and then use high-resolution infrared spectroscopy as an indirect probe of the disc. Recently available near-infrared instrumentation on 8m class ground-based telescopes, and far-infrared spectroscopy with the Spitzer space telescope can now provide enough sensitivity to allow some of the most basic questions to be answered.

Title: Exploiting the WFCAM, HARP and Spitzer 'glimpse' galactic plane surveys

Supervisors: Bill Dent, Andy Longmore

Astronomers have been remarkably unsuccessful to date in identifying the collapse status and young star content of low-mass, isolated dark clouds, frequently calling clouds "starless" only to find signs of activity on more careful examination. This project is to exploit the data from the WFCAM (Wide Field Infrared Camera), the HARP Galactic Plane Survey (GPS) and Spitzer's GLIMPSE legacy survey to answer the question. 'Why are some dark clouds and globules populated with protostars and YSOs whereas other nominally identical clouds are bereft of star formation?'

Title: Instrumentation Projects

Supervisors: Gillian Wright, Susanne Ramsay Howat, Andy Longmore, Eli Atad

A special feature of the collaboration between the IfA and the UKATC is the opportunity for PhD students to work on leading-edge instrumentation, while retaining the connection to a wide range of active astronomical applications. Some very successful PhDs have already resulted from this arrangement, which is of especial importance in training the UK's next generation of instrument scientists. The UKATC is experienced in helping students to gain intellectual ownership of their work, while making important contributions to a large instrument. Particularly timely opportunities at present are KMOS, a multi-object near-IR spectrometer for ESO VLT; MIRI, a mid-infrared spectrometer for the James Webb Space Telescope and R&D in technologies required for ELTs, such as in optical metrology, Smart Focal Planes and system modelling. In addition there are new opportunities to work on projects resulting from the SUPA Technol ogy Development appointment within the UK ATC held through the IfA.

Title: Galactic structure from stellar proper motions

Supervisors: N Hambly

Stellar proper motions measured to faint limits over wide angles enable detailed studies of the structure of our Galaxy. Luminosity functions (and hence mass functions) of various kinematic populations and different luminosity types can provide clues as to the contribution to total mass made by different populations, and also to the possible contribution of stellar remnants to dark matter problems. We have a number of wide field datasets available at Edinburgh that can be employed in such work. Example topics to be studied may include:

(i) There is some evidence for a population of cool white dwarf stars in the halo of our Galaxy. This has important implications for halo dark matter models, disk rotation curves and the evolution and structure of spiral galaxies. White dwarfs provide a natural candidate for the MAssive Compact Halo Objects (MACHOs) that are observed in microlensing experiments. The wide field datasets will be used to measure the space density of these stars. It will then be possible to measure to what extent cool white dwarfs contribute to the total halo mass density required to explain the MACHO and rotation curve results.

(ii) The hypothesis detailed in i) is naturally controversial. The contribution made by old disk and thick disk white dwarfs to the population of high velocity, cool white dwarfs is currently unknown. The same wide field datasets can be used to examine the cool stellar members of these respective populations.

It will be possible to draw some conclusions as to the star formation history of the distinct kinematic components of the Galaxy, and to refine their age estimates, for example by removing thick disk and halo contamination from the disk WD luminosity function.

This project will involve extensive use of computers to process large catalogue datasets. It is probable that some experience will also be gained in follow-up observations of stellar objects using large aperture telescopes.

Title: The formation and evolution of protoplanetary accretion discs

Supervisor: Ken Rice

Discs around young stars play a role in the transport of angular momentum outwards, allowing mass to accrete onto the newly forming star, and are also the sites of planet formation. In this project we will use numerical simulations to model the collapse of molecular cloud cores to study the formation of protostellar discs. The main aim will be to determine disc structure and disc masses to see if angular momentum transport could indeed be driven by disc self-gravity. We will also study if the FU Orionis outburst could be an indication of a phase of rapid mass accretion driven by the gravitational instability.

We will also use various thermodynamic approximations to study if these very young discs could play an important role in planet formation. In particular we will consider if gaseous planets (and possibly brown dwarfs) could form directly via gravitational collapse. We will also consider how a self-gravitating phase may influence the growth of planetesimals that will ultimately coagulate to form terrestrial planets or the cores of gas giant planets.

Title: Hidden quasars in new infra-red surveys

Supervisors: Andy Lawrence, Makoto Kishimoto, Jim Dunlop, Philip Best

Evidence from a variety of sources suggests that the majority of quasars are hidden behind obscuring dust, and that the fraction obscured is a strong function of luminosity. This may be due to a "fat molecular torus" surrounding all quasars, whose thickness depends on luminosity, or due to lower-power quasars being more likely to be smothered because of their evolutionary history. As well as being important for understanding the physics of quasars, this makes a big difference to our understanding of the X-ray background, and the growth of black holes with cosmic time. An opportunity to resolve these problems comes from analysis and follow up of the new generation of Infra-Red surveys (UKIDSS and Spitzer). The PhD student will develop methods for selecting quasars from these surveys, follow up samples with spectrsocopic observations, and compare results with a variety of model predictions.

Title: Revealing quasars with polarization

Supervisors: Makoto Kishimoto, Andy Lawrence

How a supermassive blackhole powers a quasar or an Active Galactic Nucleus, both radiatively and kinetically (e.g. winds and jets), still remains uncertain. One fundamental difficulty has been that, since the central engine is yet to be spatially resolved, we always have strong, contaminating emissions from the surrounding regions. These essentially bury and hide crucial signatures from the engine.

This project exploits our new technique to obtain contamination-free, naked spectra of a large AGN sample. It utilizes polarization which is confined only to the central engine's spectra, thus eliminates all the contaminations. The PhD student will analyze the optical and infra-red data from the new spectropolarimetric surveys and deep follow-up observations with 8-10m telescopes. With this first ever big sample of undisguised AGNs, the student will try to construct a new correct picture of these active nuclei of galaxies.

Title: Narrow-band imaging of star forming galaxies at redshifts 1 to 9

Supervisors: Philip Best, Rob Ivison

The new WFCAM instrument on UKIRT is an unique facility providing wide-field imaging in the near-infrared bands. Using existing narrow-band filters we are using this instrument to carry out a survey of H-alpha line-emitting galaxies at high redshift, in the COSMOS and UKIDSS UDS fields; this is the most efficient and accurate means of measuring the cosmic star formation rate at these early epochs, and will provide an order of magnitude improvement on previous measurements. We are currently in the process of purchasing additional custom-made narrow-band filters, for which we have been awarded telescope time to extend our survey across a range in redshift, yielding combinations of [OII]3727, [OIII]5007 and H-alpha coverage of slices at z=0.84, 1.47 and 2.23 as well as potentially detecting the first galaxies to form in the Universe, through Ly-alpha emission at z=8.90. The student will play a leading role in the observations and data reduction of this survey, as well as follow-up studies of the star forming galaxies detected.

Title: Host galaxies and interactions of AGN

Supervisor: Philip Best

A small fraction of galaxies exhibit extremely powerful radio emission, associated with accretion of material onto a supermassive black hole at the centre of the galaxy. These are known as radio galaxies, and possess jets of relativistic particles which drill their way out from the centre of the galaxy through the interstellar and intergalactic media. At high redshifts, radio galaxies are found to display an excess of ultraviolet emission, which is elongated and aligned along the radio axis. This is believed to arise from a combination of scattered light from the obscured active galactic nucleus and more local emission mechanisms arising from the interaction of the radio jets. The aims of this project are to study in detail the nature of this ultraviolet emission, and to investigate the feedback of energy that active galaxies provide into their surroundings and how this may influence the process of galaxy formation and evolution in general. The initial part of the project will be concerned with analysing very deep (~6 hour) spectropolarimetric observations using ESO's Very Large Telescope, of a sample of 7 radio galaxies with redshifts z~1.5. These are some of the deepest observations ever taken of distant active galactic nuclei. Later parts of the project will build towards exploiting LOFAR, the new low frequency radio telescope currently under construction in the Netherlands.

Title: The Physics of the Dark Ages

Supervisor: Avery Meiksin

The first sources of radiation will reveal themselves through their impact on the neutral intergalactic gas. This project involves the computation of their impact on surrounding gas with a view to predicting their 21cm signatures that may be detectable by current and projected large radio telescopes.

Title: Galaxy populations in X-ray clusters

Supervisor: Bob Mann

The XMM Cluster Survey (XCS) is a major, international project to study clusters of galaxies found serendipitously in archival X-ray data from the XMM-Newton satellite. The quality and quantity of the data in the XMM-Newton archive make the XCS the ideal basis for a wide range of analyses using clusters, and the XCS team is currently pursuing a number of scientific goals, ranging from the estimation of cosmological parameters to the detailed study of the evolution of cluster galaxies.

The first XCS cluster catalogue has recently been completed. It comprises over 1600 new cluster candidates, making the XCS the foremost cluster catalogue in existence. The optical/near-IR follow-up of this catalogue is well underway, centring on a major allocation of imaging time on US NOAO 4m-class telescopes and spectroscopic observations on 8m-class telescopes in Hawaii and Chile. We plan to supplement this on-going programme with a major proposal for near-infrared imaging data from the WFCAM camera on the UK Infrared Telescope.

This is an ideal time for a new PhD student to join the XCS team and to participate in the optical/near-IR follow-up programme, and in the analysis of the data (imaging and spectroscopy) it will yield. This project will focus on two topics related to the properties of cluster galaxy populations - the study of the Brighest Cluster Galaxies in the XCS clusters, and the variation of the cluster colour-magnitude diagram with the cluster X-ray luminosity - but there will be scope for some involvement in other analyses being conducted by the XCS team.

Title: The SCUBA-2 Debris Disk Legacy Survey

Supervisors: Wayne Holland, Bill Dent

Many stars are known to be surrounded by cold dust disks which are the result of collisions between large bodies (asteroids and comets) orbiting the stars. By studying the location and morphology of these disks we can provide crucial information about the outcome of planet formation in these systems. The first real pioneering work is this area was carried out using the SCUBA camera, developed here in Edinburgh. Although this work revolutionised this field of astronomy current instrumentation has lacked the sensitivity to allow nothing more than a handful of stars to be studied.

This situation is about to be dramatically transformed with the advent of the next generation camera, SCUBA-2. This revolutionary instrument, the world's first `CCD-style' submillimetre-wave camera (with ten thousand pixels) is currently being completed here in Edinburgh, and is due to commence science operations in Hawaii in early 2007. Wayne Holland is the lead scientist on both the SCUBA-2 project and an approved Legacy Survey to investigate dust disks around 500 nearby stars - The SCUBA-2 Debris Disk Legacy Survey - the search for the cold dust emission that is indicative of the presence of planetary systems.

The survey is expected to begin in the spring 2007, and so the timing is perfect for a new PhD student to join this project. The student would play a key role in the detailed survey design, carrying out observations in Hawaii at the telescope, and analysing and interpreting the images from the observations.

Title: Probing the Dark Universe with Gravitational Lensing

Supervisors: Andy Taylor, Alan Heavens, John Peacock, David Bacon

One of the most promising ways to study the properties of the dark matter, which dominates the matter component of the Universe, and the mysterious dark energy, which is responsible for the observed acceleration of the Universe, is via gravitational lensing. The gravitational potential field of matter distorts the images of distant galaxies. We have developed and applied methods to use this effect to map the 3-D dark matter distribution and determine the cosmological parameters. In particular, the geometry of lensing depends on the nature of the dark energy and so can be used as a probe. We are offering two projects for two students. The first is more theoretical, developing a new analysis for the rapid analysis of upcoming massive data-sets, and modelling gravitational lensing in simulated universes to test these methods, and finally applying them to new data. The second is more data-orientated; building up a massive new data-set with Europe's largest survey telescope, the VST, and using it to reconstruct the 3-D dark matter distribution and study the structure of dark matter haloes around galaxies.

Title: Modelling the Dark Energy

Supervisors: Andy Taylor, Arjun Berera

In the last few years it has become clear to cosmologists that the energy budget of the Universe is dominated by a mysterious, negative pressure 'dark energy', causing the expansion to accelerate. A number of speculative ideas have been proposed to explain what this dark energy is due to: new fields in particle physics, changes in gravity due to extra dimensions, variations in vacuum energy in the multiverse, and nonlinear gravitational back-reaction due to structure. This project is to explore the possible particle physics solutions to dark energy, and develop the theories to predict what future experiment should see. In addition we would like to see if future experiment can distinguish between the various possibilities, or if some are in fact indistinguishable. The student should ideally have a background in particle physics and cosmology.

Title: Exploring the formation epoch of massive galaxies with UKIDSS

Supervisors: Jim Dunlop, Ross McLure, Michele Cirasuolo

One of the hottest topics in observational cosmology is the question of when the most massive galaxies in the Universe first formed. Indeed, recent observational evidence suggests that massive galaxies were in place earlier, and in greater numbers, than predicted by the latest galaxy formation models. However, our current knowledge of high-redshift galaxies is based on multi-wavelength observations of very small areas of sky, which may not provide a representative picture of the high-redshift Universe.

Fortuitously, this situation is about to be revolutionised by the on-going UKIDSS Ultra-deep survey (UDS), which will provide near-infrared imaging with an unprecedented combination of sensitivity and large area coverage. By combining the UDS data with existing deep optical imaging, and mid/far infrared data from the Spitzer space-telescope, the goal of this project is to determine the formation epoch of massive galaxies and unveil the history of stellar mass assembly. The PhD student will have the opportunity to actively take part in the UDS observations at the UKIRT telescope on Mauna Kea, Hawaii.