Compact Objects and Time Domain Astronomy
The School of Physics and Astronomy at the University of Southampton offers postgraduate studies (Ph.D.) in a variety of fields in astronomy and space science, including observational and theoretical astrophysics of our own and other galaxies, as well as the study of planetary magnetospheres. We also have a strong interest in high-energy, space-based astrophysics in general and in particular in the major gamma-ray satellite INTEGRAL.
Possible research topics are generally outlined by the research interests of our members of staff. If you have any questions about any particular topic you are welcome to contact people directly. Dr Francesco Shankar would be glad to respond to any (in)formal enquiries.
More general information on postgraduate work in the Physics and Astronomy department at Southampton is available. For more information about the University and its surroundings, look at the University home page. Have a look at the astronomy group's home page to find out more on what we do here.
Several PhD places will be available in the astrophysics group this year, with projects chosen from among those listed below. Candidates need not express a preference for project/supervisor before interviews are held. Applications will be reviewed at the end of January and successful candidates invited for interview shortly afterwards. Late applications may be considered. We also offer the possibility to co-host PhD studentships in collaboration with ESO, Europe’s flagship observatory. PhD projects will typically be supervised by a member of staff of the astro group and one at ESO in Garching near Munich (Germany) or Santiago (Chile). Students will have the opportunity to work two years in an international environment in Germany or Chile before finishing their last year at the University of Southampton. Please contact a member of staff if you are interested.
Scroll down to view the PhD projects available this year
For further information, please contact:Dr Francesco Shankar
Room 5067 (building B46);
School of Physics & Astronomy
University of Southampton
SO17 1BJ, U.K.
How to apply
To apply you will need to get an application form (which asks brief details of your past courses) and the names and addresses of two people who can provide you with a reference (you don't need to upload references yourself, the system will automatically send out a request to the contacts you have provided). The key aspects are (a) what degree course you have done, and any relevant components, especially project work, and (b) your references. Do not worry if you do not know exactly what you want to do. It would be surprising if you did!
If you are interested in applying and would like an application form and further information, please fill in the on-line form, apply to the "PhD Physics" programme, and specify "Astrophysics" in the "Topic of field or research" section to have your application directed to the astronomy group. For part-time research, use this form instead. To apply for the Mayflower Scholarship, use this form.
For more information on how to apply and online application form please visit the University web page.
Black holes in our Galaxy have masses between 5 and 15 times that of
our Sun, and are formed when a massive star explodes in a Supernova. A
black hole is so massive and confined in such a small volume in space,
that not even light can escape its gravitational
attraction. Fortunately, some black holes are in binary systems with a
star similar to, or smaller than our Sun. If the black hole and the
companion star are close enough, the strong gravity produced by the
black hole will slowly "suck" gas from its companion, deforming it
into a pear-shape star. The gas pulled off by the black hole does not
fall directly into it, but swirls in like bath water around a
plug-hole, forming a disk of gas which astronomers call accretion
What are the fundamental physics that rule accretion disks? What are the physical ingredients needed to produce ultra-fast winds and jets? The PhD student will join the group of high-energy astrophysics in order to tackle some of the most fundamental questions of accretion disk physics. To do so, the student will use high-time resolution data from NASA's newest X-ray instrument "Neutron star Interior Composition Explorer", in combination with data from state-of-the-art optical, infrared and Radio facilities.
Neutron stars (NSs) are compact objects. The tiny NSs being no more
than 20-30 km in diameter but containing masses of 1 to 3 times the
Sun, represent extremes of gravity, pressure and density, making them
the only stars where matter burns on the outside. Fortunately, some
NS have close companion stars; gas from these stars, attracted by the
compact object strong gravity, funnels and spirals towards it, forming
an accretion disk. These systems are called NS low-mass X-ray binaries
(LMXBs); the most powerful phenomena we observe from them are directly
related to these accretion disks, as a large amount of gravitational
energy is released when the matter approaches the compact object. This
causes the inner accretion disk to reach temperatures as high as 100
million degrees and therefore to emit the bulk of the energy in the
X-ray band of the spectrum. It is the flow of this accreting plasma
onto the NS which provides one of the very few opportunities to
directly probe the properties of the tiny (few km) regions where we
can "see" General Relativity effects in action in otherwise
This project will make use of high-time and high-energy resolution X-ray data from the Neutron star Interior Composition Explorer (NICER) to understand the physics of millisecond X-ray variations seen only around NS. NICER is the state-of-the-art NASA mission dedicated to the study of the extraordinary gravitational, electromagnetic, and nuclear physics environments embodied by neutron stars. The student will join the high-energy astrophysics group at Southampton, and will have the opportunity to collaborate with researchers from around the world.
The Earth's magnetic field forms a cavity in the solar wind called the magnetosphere; the interaction between the solar wind and the magnetosphere is ultimately responsible for the dynamics of near-Earth space, including variations in the intensity of the radiation belts and the most spectacular displays of the aurora (the northern and southern lights). The nature of these interactions depends on the orientation of the magnetic field associated with the solar wind (the interplanetary magnetic field, or IMF); a "southward" orientation of the IMF (opposite to the Earth's magnetic field) is preferential for many magnetospheric processes, but the IMF direction is highly variable, and the dynamics of the magnetosphere under northward IMF conditions are, in comparison, poorly understood.
Recent papers have begun to challenge the textbook paradigm of how the magnetosphere is structured under northward IMF, finding that uncharacteristically hotter/higher density plasma can be observed in the lobes, associated with perplexing "high latitude" auroral emissions which lie poleward of the main auroral region. The mechanisms causing both the plasma structure and the high latitude auroral emissions are intensely debated. The aim of this project is to use in situ satellite data from spacecraft such as the European Space Agency's Cluster mission to determine and explain the structure of the magnetotail during the more complex intervals associated with northward IMF. This will begin with a statistical classification of the plasma environment during northward IMF conditions, and will lead on to a comparison with global scale auroral datasets. We expect this work will lead to a significant contribution to our understanding of the magnetosphere's response to northward IMF conditions.
The Earth's aurora borealis are a spectacular natural phenomenon, caused by energy deposition from the 'solar wind' into the upper atmosphere through the process of Joule heating. Recent work at Southampton has shown that electric fields on temporal scales of hundreds of milliseconds can be determined by auroral observations made by state-of-the-art instruments. So far, only simple electric field structures have been considered, but more complex parameterizations could quantify spatial variability on scales of hundreds of metres and therefore reveal the true contribution to atmospheric heating made by Joule heating. The project will involve fieldwork on the Arctic archipelago of Svalbard, in order to operate the auroral cameras and supporting ionospheric radars; training will be provided in Arctic survival and safety techniques, and operation of the optical and radar instrumentation. Please note the early deadline for applications for this project (Friday 4th January).
In collaboration with the Indian astronomy centre for excellence IUCAA, we offer exchange opportunities for students to work on novel studies of black holes with state-of-the-art optical and X-ray camera. Students will spend at least 1 year at Southampton and up to 2.5 years at IUCAA in Pune, India, working with members of the Indian space mission for studying black holes, AstroSat, as well as coordinates observations and travelling between UK/India/South Africa/Chile/space telescopes.
Black holes are the most compact objects known. So, physical conditions in their surroundings can change rapidly. The aim of this project is to capture these rapid changes by making state-of-the-art high frame-rate multi-colour 'movies' of black holes in outburst. Observations across the electromagnetic spectrum including X-rays, optical, infrared and radio data are needed to capture the full energy release of black hole emissions both from the accreting material, and from outflowing fast relativistic jets.
You will have the opportunity to plan and execute multiwavelength observations, analyse and interpret the data, and to constrain theories of black hole growth and launching mechanisms for relativistic jets. For more details on this growing field of rapid time domain astronomy, please follow the links below.
Our understanding of binary star evolution is still very fragmentary, an ad hoc amalgam of single star evolution plus parameterised accounting for the effects of interaction. Accretion disc physics remains to be tested in detail, and basic orbital parameters of the majority of accreting binaries remain unquantified. Studying these systems is critical to understanding the progenitors of Gravitational Wave sources.
Next-generation surveys including LSST (the Large Synoptic Sky Survey) have the potential to be game-changers for Galactic evolutionary studies, including compact object binaries. This project will focus on (1) realistic simulations of LSST prospects for the Galactic X-ray binary population, (2) devising classification and follow-up strategies for newly discovered Galactic transients, and (3) carrying out key multiwavelength follow-up of new outbursts. You will have the opportunity to join the LSST:UK consortium and learn about big-data techniques, in addition to developing tools to analyse LSST data. This work will ultimately be used to constrain binary population synthesis models over parameter space that is newly opened up by these surveys.
All quasars are powered by the same central engine: a supermassive black hole that is surrounded and fed by a luminous accretion disk.
Approximately 15% of all quasars exhibit clear evidence for powerful outflows driven from these disks, in the form of broad, blue-shifted absorption lines. However, these so-called "broad absorption line quasars" (BALQSOs) are just the tip of the iceberg: since disk-driven winds cannot be spherical, BALQSOs are just the sub-set of quasars viewed at a particularly favourable orientation.
In reality, all quasars are likely to drive such winds. This is important, because these outflows provide a key feedback mechanism: they can remove significant amounts of mass, energy and angular momentum from the quasar and inject it into the surrounding (inter-)galactic medium. However, despite their importance, we know almost nothing about these accretion disk winds.
This work will be carried out in the context of an established collaboration and will use an existing, state-of-the-art Monte Carlo radiative transfer code. The ultimate goal we are pursuing is to determine the fundamental parameters of quasar accretion disk winds and thus shed light on how they regulate the fueling of supermassive black holes and the feedback of energy into their environment. (Image credit: NASA, and M. Weiss, Chandra X-ray Center)
Accreting white dwarfs (AWDs) are numerous, bright and nearby, making them excellent laboratories for the study of accretion physics. Since their accretion flows are unaffected by relativistic effects or ultra-strong magnetic fields, they provide a crucial "control" group for efforts to understand more complex/compact systems, such as accreting neutron stars (NSs) and black holes (BHs).
Surprisingly, it has recently become clear that these superficially simple systems actually exhibit the full range of accretion-related phenomenology -- outbursts, disk winds, jets, variability -- that is also seen in accreting NSs and BHs. Given this rich set of shared behaviour, it is reasonable to hope that much of accretion physics is universal.
The goal of this project will be to test and develop this emerging picture. This will involve gathering, analysing and interpreting observational multi-wavelength data, using both ground-based and space-based observatories (such as Hubble and Chandra). If AWDs really do provide a viable and accessible model for disk accretion in general, such observations will yield qualitatively new insights into the nature of accretion physics and associated outflows. (Image credit: David A. Hardy http://www.astroart.org & Science and Technology Facilities Council. )
The two processes which most affect the appearance of our universe are star formation and accretion of matter onto SMBHs. These processes, and their interaction, are best studied in nearby galaxies where we have the best sensitivity and highest linear resolution.
For these purposes we are carrying out LEMMINGS, the second largest legacy survey with the eMERLIN radio telescope and the deepest and highest resolution radio survey ever carried out on nearby galaxies. With parsec-scale resolution we are observing all 280 northern galaxies from the Palomar sample, the best selected sample of nearby galaxies. We also lead a deep Chandra X-ray survey and extensive HST observations exist on all galaxies. Amongst the aims, we will study the origin of jets and other strange radio morphologies seen in the nuclei of galaxies and will investigate the relationship between the radio emission (coming mainly from jets) and X-ray emission (powered by accretion through a disc), ie 'disc-jet coupling'.
Southampton are also co-PIs of eMERGE - the deepest and highest resolution cosmological radio survey and the largest legacy survey being made with eMERLIN, centred on the Hubble Deep Field North and with extensive optical and X-ray observations. eMERGE is designed to study the cosmic evolution of the star formation rate and of SMBHs and observations are currently being analysed on the Southampton IRIDIS-5 supercomputer. There may be opportunities to participate in this programme. (Image: Artist's impression of an inner accretion flow and a jet from a supermassive black hole. Credit: ESO/L. Calcada.)
Galaxies in the local Universe appear with a variety of morphologies from discs to massive spheroids (ellipticals).
The origin of bulged galaxies is still a matter of debate.
This project aims at probing the formation and evolution of bulged galaxies
using a cutting-edge methodology based on extensive, advanced semi-empirical models which make use of sub-halo abundance
matching and halo occupation distribution techniques.
The main objectives of this proposal are to:
- Analyse, in a cosmological context, an array of key physical processes to form and evolve bulged galaxies, such as mergers, bar/disc instabilities, disc regrowth, clumpy accretion, morphological and/or halo and/or environmental quenching. Several of the latter physical processes are still nearly unexplored in this context.
- Compare the outputs of each different model with the statistical, spectral, morphological, structural, and environmental properties of bulged galaxies.
We will make extensive use of new, unique, and comprehensive data sets available to our group from, e.g., SDSS and COSMOS, specifically catalogued for bulged galaxies in different environments and redshifts.
Supermassive black holes, extreme singularities of spacetime, of the order of a million to a billion solar masses, are lurking in the cores of most galaxies, including our own Milky Way. The masses of supermassive black holes seem to be tightly correlated with several host galaxy properties, in particular to the characteristic random motions (velocity dispersion) of stars. This discovery strongly favours quasar-feedback models, which naturally predict a tight correlation with velocity dispersion, over merger-driven models of black hole growth which would instead predict a tight correlation with stellar mass.
Via the use of advanced semi-empirical models, which make use of sub-halo abundance matching, coupled to the outputs of high-resolution N-body simulations, this project aims at determining the relative roles of quasar feedback and galaxy mergers in setting the scaling relations with velocity dispersion. In turn, the project aims at constraining the radiative efficiency (and thus the spin) of black holes.
This project will also set very stringent constraints on the gravitational wave background from supermassive black hole binaries, of capital importance for the next gravitational wave detectors (eLISA). The student will become part of the next-generation European space galaxy missions, Euclid and Athena. (Cartoon image of two merging supermassive black holes from Astronomynow.com).