Ph.D Projects

Annihilation of Dark Matter
Zhao, Dr Hongsheng - hz4@st-andrews.ac.uk

A main diagnostic of the particle dark matter is its annihilation rate, which depends sensitively on the dark matter density profile. The student will explore various density models of the dark matter, taking into account the effects of black holes and baryonic dynamics.
Atmospheres of Very Low Mass Objects: Brown Dwarfs and giant gas planets
Helling, Dr Christiane - ch80@st-andrews.ac.uk

These projects will investigate the atmospheres of planets and Brown Dwarfs which contain the fingerprints of their physics and chemistry. Atmospheres of Brown Dwarfs and giant gas planets are forming clouds that can be made of silicate and iron dust rather than of water. Any clouds leave a trace of an individually depleted gas which determines the spectral appearance of the planet/Brown Dwarf as well as it does influence the dynamic behaviour of the atmosphere.

Using a detailed model of dust formation, possible topics include:

1) Atmosphere's response on planetary evolutionary events
like volcanism, dust/gas accretion, mass loss during star-planet interaction

2) Modeling atmospheres of planets/Brown Dwarfs in nearby galaxies,
like the Large and the Small Magellanic Cloud

3) Modeling planetary atmospheres under the influence of disk evolution
combining results from protoplanetary disk evolution model with atmosphere modeling
Charge separation in turbulent volcano plumes
Helling, Dr Christiane - ch80@st-andrews.ac.uk

We will study the charge separation and lightning processes in volcano plumes. The results will help us to understand the electrification of extrasolar atmospheres.

see also LEAP PhD positions
Coronal structure of low mass stars
Cameron, Prof Andrew - acc4@st-andrews.ac.uk
Jardine, Prof Moira - mmj@st-andrews.ac.uk

Low mass (fully convective) stars appear to generate magnetic fields whose surface distributions are fundamentally different to those of higher mass stars. We will use existing Zeeman-Doppler maps of these surface magnetic fields to model the coronal structure and X-ray emission of these stars.
Diffuse ionized gas in galaxies
Wood, Dr Kenneth - kw25@st-andrews.ac.uk

Extensive layers of diffuse ionized gas are observed in the Milky Way and other galaxies. This project will study the structure, ionization, heating, and dynamics of diffuse ionized gas using a combination of 3D Monte Carlo radiation transfer codes and recent 3D dynamical models of a supernova driven ISM.
Echo Mapping of AGN
Horne, Prof Keith - kdh1@st-andrews.ac.uk

Light travel time delays enable micro-arcsecond mapping of accretion disks and broad emission-line regions around the super-massive black holes in the nuclei of active galaxies. RoboNet provides the UK with unique datasets for measurement of black hole masses, accretion rates, and luminosity distances. The student will acquire and analyse such datasets, using parameterized models and Hornes maximum entropy fitting code MEMECHO.
Forming comet belts around nearby stars
Cameron, Prof Andrew - acc4@st-andrews.ac.uk
Greaves, Dr Jane - jsg5@st-andrews.ac.uk

Collisions of comets create dust belts that can be imaged at submillimetre wavelengths. The SCUBA-2 Legacy Survey starting early-2010 will explore what kinds of star have comets and if this is a signpost of extrasolar planets. We will help analyse the database of 500 stars to identify underlying stellar influences.
Ionisation in atmospheres across the star-planet mass boundary
Helling, Dr Christiane - ch80@st-andrews.ac.uk

The ionisation of the atmosphere depends on the local temperature which, in turn, depends on the effective temperature. We will study how the atmospheric electrification changes with decreasing effective temperature from the M-dwarfs into the Brown Dwarfs into the planetary mass regime.

See also LEAP PhD positions
Magnetic cycles in young stars
Jardine, Prof Moira - mmj@st-andrews.ac.uk
Wood, Dr Kenneth - kw25@st-andrews.ac.uk

In very young stars, material accreting from a surrounding disk is channelled by the star's magnetic field onto the stellar surface. We will use recently-acquired magnetic maps of these stars to model the impact of magnetic cycles on this accretion process.
Mass Distribution of the Galaxy
Zhao, Dr Hongsheng - hz4@st-andrews.ac.uk

The mass distribution of the Galaxy is being / will be mapped out in great detail in the next decade with the numerous surveys of the Galaxy, including Segue, RAVE, GAIA, and completed ones like 2MASS, DENIS. A model for the potential and phase space of the galaxy is essential to bring various pieces of information together. The student will develop such models building on experience from existing models.
Microlens Survey for Cool Planets
Horne, Prof Keith - kdh1@st-andrews.ac.uk

Intensive monitoring of Galactic Bulge microlensing events is being used to discover cool planets in 1-5 AU orbits around the lens stars. Our PLANET/RoboNet team has just discovered a 5 earth-mass planet. In the next 4 years we aim to measure the abundance and mass function of cool planets to test theories of planet formation and migration. The student will work with our team to acquire and analyse observations, fit microlens models to characterize the planetary and other anomalies.
Spindown of solar-type stars with age
Cameron, Prof Andrew - acc4@st-andrews.ac.uk
Greaves, Dr Jane - jsg5@st-andrews.ac.uk

Solar-type stars are born with a variety of spin rates. Magnetic braking theory predicts that the spread should narrow after a few times 10^8 y but observational surveys remain scanty. We will compile a complete survey of rotation periods in open clusters spanning the critical age range using photometry from the WASP project, and for field stars using publicly-released data from the CoRoT and Kepler space missions. The ultimate goal is to calibrate stellar spindown accurately enough for use in determining the ages of exoplanet host stars.
Star formation in dwarf galaxies
Bonnell, Prof Ian - iab1@st-andrews.ac.uk

This project is to develop the first models of resolved star formation on galactic scales. This will involve modelling a full galactic potential and how it drives the formation of molecular clouds and the onset of gravitational collapse and star formation. feedback from ionisation and supernova will be included to assess molecular cloud lifetimes and star formation efficiencies.
Star-Planet Interaction
Jardine, Prof Moira - mmj@st-andrews.ac.uk

Tau Boo is the only star for which we have been able to track the full cyclic reversal of the stellar magnetic field. This system is also well-known, however, because it hosts a Hot Jupiter that is so close to the star that it may lie within the stellar corona. What is the nature of the interaction between the star and planet in this case and is it related to the puzzling nature of the very short magnetic cycle? This project will investigate tau Boo and other similar star-planet systems.
Structure and evolution of protoplanetary disks.
Greaves, Dr Jane - jsg5@st-andrews.ac.uk
Wood, Dr Kenneth - kw25@st-andrews.ac.uk

Understanding the structure, composition, and dynamics of protoplanetary disks are crucial for planet formation theories. This project will combine dynamical models of disks with 3D radiation transfer and new multiwavelength imaging and spectroscopy to study dust growth and settling, disk-planet interactions, and signatures of massive, self-gravitating disks.
Studying planet populations by means of gravitational microlensing
Dominik, Dr Martin - md35@st-andrews.ac.uk

With more than 400 planets orbiting stars other than the Sun known (as of March 2010), observing campaigns now need to evolve from the pure detection of planets to studies that allow to infer the statistical properties of the underlying populations that are being probed. Only by comparing a wide planet census with model predictions of planet formation and evolution, will we be able to understand the origin (and future!) of habitable planets, and Earth in particular. Due to their probabilistic nature, gravitational microlensing experiments are particularly challenging, but they are suited to provide insight that remains hidden to any other known technique, with a sensitivity reaching even below Earth mass, and the possibility to spot signatures of planets orbiting stars in other galaxies. The realisation of a fully-deterministic observing strategy is a necessary prerequisite for measuring planet abundances. Over the recent years, we have been working on the development of the world-leading technology for implementing an automated microlensing campaign that is carried out by means of our RoboNet-II and MiNDSTEp telescope networks, and informed about the targets to be observed by the publically-accessible ARTEMiS system. Two specific topics currently call for special attention:

1) Further development of ARTEMiS is required to provide a target recommendation for a non-proprietary heterogeneous network of telescopes according to a user-defined strategy, the currently available data, the individual telescope capabilities, and the observability. Gravitational microlensing is a showcase application for modern telescope scheduling, and by its strong demands on flexibility and reaction time leads to pioneering concepts that can be of far more general use. Moreover, ARTEMiS not only provides tools to astronomers, but also brings forefront science to the general public.

2) Imperfections in the data reduction lead to various types of spurious signals, which either need to be properly identified and separated from real variations, or to be treated statistically as a form of background noise. The low-mass sensitivity limit of our campaigns crucially depends on how well we understand this. Moreover, a proper understanding of false positives will make a difference on the efficiency of our monitoring programme by allowing more appropriate decisions based on real-time data.

Further Links:

MiNDSTEp www.mindstep-science.org
ARTEMiS www.artemis-uk.org
The link between planetary atmosphere and planetary magnetic field
Helling, Dr Christiane - ch80@st-andrews.ac.uk

We will study how a brown dwarf and a planetary atmosphere interacts with a planetary magnetic field and how this might be observable.

See also LEAP PhD positions
The role of gas-rich major mergers in building elliptical galaxies
Wild, Dr Vivienne - vw8@st-andrews.ac.uk

The dominant physical processes responsible for the growth and evolution of galaxies over the history of the Universe are not well understood. Popular theories suggest gas-rich galaxy mergers are key in triggering star formation, altering the morphology of the galaxies, and causing supermassive black hole growth, however direct observational evidence remains scarce.

The aim of this project is to determine the true role of mergers in defining the galaxy population around us today. This will involve the analysis of the soon-to-be-completed spectroscopic and multi wavelength galaxy survey GAMA, and the concurrent analysis of hydrodynamic models of galaxy mergers with which to compare the observational data.

The project may involve extended stays in Finland or Germany to work with colleagues on the development of the models and image analysis techniques, or Australia to work on analysing results from the GAMA survey. At the end of the PhD, the student will be well placed to apply the analysis techniques that they have developed to the most important high-redshift datasets of the next decade with the launch of JWST in ~2016-2018.

Links:
The GAMA survey: http://www.gama-survey.org/
The James Web Space Telescope http://www.jwst.nasa.gov/

This project may be funded by the European Union and St Andrews University and we therefore welcome applications from all nationalities.

Note that Vivienne will be moving to St Andrews as a lecturer from January 2012. Please see her website for more information about her research: http://www.roe.ac.uk/~vw/
Triggering of star formation
Bonnell, Prof Ian - iab1@st-andrews.ac.uk

There are several outstanding issues in current models of star formation. One of these is the role of feedback from young stars in producing subsequent generations of young stars. Triggering of star formation through supernova events is likely to be the dominant mechanism. Numerical simulations of SNII impacting on molecular clouds and the triggering of star formation will be used to develop physical models, and ultimately observational predictions and tests of the process.
Wide-angle search for transiting planets
Cameron, Prof Andrew - acc4@st-andrews.ac.uk

The WASP project (http://www.superwasp.org) is a consortium comprising 6 UK universities and 3 overseas observatories. We use two arrays of wide-field camera lenses backed by large-format CCDs to perform high-precision photometry of millions of stars each night, looking for the 1% dips in light that betray gas-giant planets whose orbital planes are close enough to the line of sight that they transit their host stars. Our current catch stands at 70 planets confirmed by radial-velocity follow-up. There is an opening at St Andrews for a PhD student to work on a combination of project infrastructure and science exploitation. Possible components of a PhD project include:
- Improving the quality of the SuperWASP photometry using image-subtraction and profile-fitting methods;
- Improving the transit detection and pre-selection criteria to eliminate astrophysical and other false positives;
- Measuring stellar spin rates and spin-orbit misalignments using time-resolved spectroscopy during transits;
- Determining the ages of transiting planet systems from the spin rates of the host stars;
- Modelling the tidal spin-orbit interaction between the closest-orbiting hot Jupiters and their host stars;
- Using high-resolution time-series transit spectroscopy to confirm the presence of planets around early-type stars;
- Reconciling the planet catch with models of the galactic planet population and observational detection thresholds;
- Modelling the infrared spectra of hot-Jupiter atmospheres for comparison with Spitzer/IRAC secondary-eclipse photometry;
- Building or using simple planetary structural models as a tool to aid understanding of the mass-radius relation for transiting hot Jupiters as a function of age, core mass, envelope metallicity, stellar irradiation etc.