PhD projects 2013
PhD projects offered for starting in 2013 are listed below. Click on the project title to see a description of the project. You are encouraged to email directly the project contact (the first supervisor, unless indicted otherwise) to discuss it with them.
Unless otherwise indicated, to email the project supervisor you can use first_name.last_name@manchester.ac.uk.
If you have ideas of your own for potential projects then please contact either a member of staff working within the relevant research area or else email JBCA Postgraduate Admissions who can put you in contact with a member of staff.
| Research Area | Project Title | Supervisor |
|---|---|---|
| Extragalactic Astronomy & Cosmology |
Cosmological Simulations of Galaxy Clusters
|
Dr Scott Kay |
|
Galaxy clusters are critical objects for developing our understanding of the
universe. As the most massive gravitationally-bound objects their
distribution is sensitive to the nature of dark energy, so many
observational surveys are being conducted (and planned) to use clusters to
measure cosmological parameters. Secondly, clusters contain the most
massive galaxies in the Universe, surrounded by a diffuse and hot X-ray
emitting plasma. Multi-wavelength observations of clusters provides
important clues to how super-massive black holes influence galaxy formation
and evolution, including their role in shutting off star formation and
heating the intra-cluster gas.
Much of our physical understanding of clusters has arisen from the development of cosmological simulation techniques and their subsequent comparison with observational data. This is an opportunity for a student to work on projects within our ongoing cluster simulation research programme. Areas of current importance include the development of hydrodynamical modelling techniques and galaxy formation physics (especially feedback from active galactic nuclei). The student will use high performance computing facilities, both locally and as part of the Virgo Consortium, based in Durham. This opportunity is especially suited to those with a keen interest in code development and numerical analysis. | ||
CBASS
|
Prof Richard Davis (contact: rjd@jb.man.ac.uk) |
|
| The C Band all sky survey CBASS is a project to observe the sky at 5 GHz in T and polarisation where the synchrotron and free-free radiation dominate. This will provide the 5 GHz channel for Planck. The lowest frequency on Planck is 30 GHz and to match the resolution of this instrument at 5 GHz requires a 6 m dish. This was not possible from the spacecraft but can be done from the ground using two 6m class telescopes in the north at Owens Valley and in the south from South Africa. We have built all the low noise amplifiers for the north telescope and the complete receiver for the south. We are observing in the north and finishing the receiver for the south. The PhD will involve hands on analysis of data from both instruments and visits to Owens valley and/or South Africa for observing and working with the receivers. The synchrotron emission from the Galaxy is the aim of this project for subtraction from the Planck maps. The old 408MHz map of synchrotron is too low in frequency to enable extrapolation to 30 GHz and it did not have polarisation. Above 5 GHz other emissions start to dominate. So this is the reason for CBand. The project is international and involves a consortium of Manchester, Oxford and Caltech USA and South Africa not far from the SKA site. | ||
New light on radio jets
|
Paddy Leahy & Ian Browne (JBCA); Robert Laing (ESO) (contact: j.p.leahy@manchester.ac.uk) |
|
|
Jets from AGN are the most spectacular and mysterious phenomena in
astrophysics. No-one could have predicted that the black holes at the
centres of galaxies would sometimes channel huge quantities of matter
and energy into a pair of well-focussed, oppositely directed outflows
at nearly the speed of light, that can travel millions of light-years
from their power sources, inflating the inter-galactic bubbles known
as radio lobes. These galaxy-scale eruptions are suspected to
play a crucial role in the formation and growth of galaxies:
specifically they are a prime candidate for the feedback connection
between the central black hole and global star formation required to
control the size and mass distribution of galaxies.
A PhD place is available to work on the international eMERLIN Legacy project devoted to solving key problems in the physics of extragalactic jets. There is an opportunity to spend up to about half of the PhD project working with Prof Laing at ESO HQ, Garching, Germany. The work will involve the calibration and map-making of the new eMERLIN data on several of the brightest radio jets, and comparing these results with the best available models and with archival results from the Hubble Space Telescope, the Chandra X-ray Observatory, and MERLIN (significant motion is expected to be detectable during the project in at least one case). Very little is known for sure about jets: how are they launched? what are they made of? exactly how fast are they going? what keeps them in a well-collimated stream from sub-parsec to megaparsec scales? What impact do they have on the interstellar and intergalactic gas, and vice versa? Our best hope for progress is to exploit the main observational signature from jets: their synchrotron radio emission, which allows radio synthesis arrays to image their structure. Recent progress has been made by detailed comparison of semi-analytical models of jets with deep radio images from the Very Large Array (e.g. Laing et al 2008, 2011), which gives convincing evidence (for the low-power "FR I" jets) that the dynamics on galactic scales is controlled by competition between acceleration by the pressure gradient in the galactic atmosphere, and deceleration from drag caused by turbulent pick-up of mass from that same atmosphere. This model implies a deceleration from relativistic speeds on scales too small for the VLA to resolve, but ideal for study with the new e-MERLIN, which will give maps of unprecedented sensitivity and resolution. | ||
Detection of Baryon Acoustic Oscillations via HI intensity mapping
|
Clive Dickinson & Richard Battye (JBCA) (contact: Clive.Dickinson@manchester.ac.uk) |
|
|
Baryon Acoustic Oscillations (BAOs) are imprinted on matter throughout the Universe. They provide a key cosmological standard ruler, that can be used to measure the expansion of the Universe as a function of redshift and therefore can constrain dark energy models e.g. the equation of state. This is one of the key science drivers for the Square Kilometre Array (SKA) that will be fully operational during the next decade. However, a new technique called "HI intensity mapping" may allow them to be detected at radio wavelengths by mapping the redshifted 21cm HI line on large angular scales. Furthermore, this could be achievable within the next few years, providing complementary information and an independent test of the cosmological model. We have proposed a single dish experiment, BINGO (BAOs using Integrated Neutral Gas Observations), that has the possibility of detecting BAOs (Battye et al. 2013). We are currently pursuing funding and site locations for the 40m dish required for BINGO. In the meantime, much preparation is required both on the instrumentation side, and on the analysis side. In particular, we need to make detailed simulations of BINGO data, taking into account the bright foregrounds and also instrumental systematic effects that could be problematic. These issues will be critical to the success of the experiment. We are also affiliated with other HI intensity mapping experiments including interferometric arrays that could be the focus of the project depending on progress with both experiments. The student will become a key member of the BINGO team and cosmology group at Manchester. Depending on your interest, and background, you will work with the BINGO team to develop simulation tools, component separation and analysis techniques, and will be involved in the design and testing of instrumentation for BINGO (e.g. testing of receivers, programming of digital backends etc.). An important aspect will be dealing with foreground contamination from our Galaxy and extragalactic radio sources. | ||
| Pulsar Astrophysics |
Finding the limits of the pulsar population
|
Dr Ben Stappers, Dr Patrick Weltevrede |
|
The Jodrell Bank Pulsar Group (JBPG) are involved in a
number of very large surveys for new radio pulsars, and the currently poorly understood
population of fast radio transients. These surveys will provide
our best understanding of the population of these sources until
the world's largest radio telescope, the SKA is built.
This project would involve the student becoming
involved in the search for new pulsars and radio transients in
one or all of these surveys
and being responsible for some of the follow up
studies. Radio pulsars are some of the most extreme
objects known and provide us with excellent tools for
studying matter at high densities, ultra-strong
magnetic fields and even for studying gravity and
spacetime itself. Using the Parkes radio telescope in
the Southern Hemisphere we are performing a very high
time resolution study of the entire sky. This survey
has already started to find many new and interesting
pulsars, including millisecond pulsars. Of particular interest
it is finding bright narrow bursts of radio emission that are located
at extragalactic distances. The origin of these sources is still unknown
but some possibilities include: annihalating blackholes, merging neutron stars, and tidal
disruption of a star by a blackhole. In the Northern Hemisphere we are using the first of the next generation telescopes, LOFAR, to search the whole of the Northern sky for new pulsars at frequencies around 150 MHz. This survey will be so sensitive that it will find the entire local population of pulsars and provide an unprecedented view of the range of pulsars which exist. We are also embarking on using the MeerKAT telescope, which is being built on one of the sites of the SKA, to search deeper than ever before for new pulsars. Altogether these surveys are going to at least double the number of pulsars known and thus reveal many exciting individual sources as well as providing invaluable information on the population as a whole. | ||
High Precision Pulsar Timing
|
Dr Ben Stappers, Dr Patrick Weltevrede | |
| Pulsars rotate with exceptional regularity which makes them ideal to be used as cosmic clocks. They have already been used to prove the existence of gravitational waves and have been used to provide some of the most stringent tests of theories of gravity. With improved techniques and telescopes new and improved tests can be pursued and we can also begin the search for the influence of gravitational waves. This project involves the student being involved in the high precision timing program of the Lovell telescope. It requires someone with good computing skills who is interested in working with instrumentation as well as analysis and interpretation of data. The Lovell telescope is part of the European Pulsar Timing Array project which is a collaboration between 5 very large telescopes in Europe to pursue the highest precision pulsar timing possible. The first key aspect of this work is achieving the maximum possible timing precision with each of the individual telescopes. To achieve the former we have recently purchased new hardware which has greatly improved the capabilities of the Lovell but which also has the possibility to be extended further with additional development which the student would be involved in. The second key aspect of the students work is will be the involvement in the Large European Array for Pulsars (LEAP) project, which aims to coherently combine all the 5 EPTA telescopes to simulate a dish which is equivalent in size to the largest telescope in the world, but which can see a greater fraction of the sky. The data from both the Lovell and LEAP will be used by the student to undertake high precision timing for studies of individual systems and we can also begin the search for a direct detection of gravitational waves. | ||
| Sun, Stars & Planets |
Magnetic reconnection and heating the solar corona
|
Prof Philippa Browning |
| Research in solar plasma physics is concerned with modelling the complex interactions of magnetic field with plasma in the solar atmosphere - in the context of the wealth of new data from space and ground-based observations of the Sun which is transforming our understanding of our nearest star. A major unsolved problem is to explain why the solar corona is at a temperature of over a million degrees Kelvin (compared with a surface temperature of about 6000 K). Coronal plasma is believed to be heated by dissipation of stored magnetic energy, but the details remain controversial. A strong candidate for an efficient energy dissipation mechanism is the process of magnetic reconnection. Stored magnetic energy is also released by reconnection in solar flares, so that flares and coronal heating may be manifestations of the same underlying physical processes. PhD projects are available to model coronal heating through reconnection, both through numerical magnetohydrodynamic simulations and through semi-analytical modelling, based on the idea that the coronal field relaxes towards a minimum energy state. Current models of energy release in unstable twisted coronal loops will be extended to more complex configurations, exploring the effects of magnetic field topology, and investigating reconnection in the partially-ionised lower solar atmosphere. | ||
Modelling the generation of high energy particles in solar flares
|
Prof Philippa Browning | |
| Research in solar plasma physics is concerned with modelling the complex interactions of magnetic field with plasma in the solar atmosphere - in the context of the wealth of new data from space and ground-based observations of the Sun which is transforming our understanding of our nearest star. Solar flares are dramatic released of stored magnetic energy in the solar corona. A challenging question is to understand how the magnetic energy is released and charged particles are accelerated to high energies in flares. We have been developing test particle models to show how particles can be accelerated in complex fields with fragmented current sheets and near magnetic null points. Reconnection is also important in laboratory plasmas, and we are also developing models of reconnection and particle energisation in spherical tokamaks, in collaboration with UKAEA Fusion. Potential student projects are available to investigate particle acceleration and magnetic reconnection in solar flares, extending current models to incorporate the effect of the feedback of the accelerated charged particles on the electromagnetic fields, and investigating different field configurations. | ||
Cluster and Massive Star Formation
|
Prof Gary Fuller | |
| Infrared dark clouds are the silhouettes dense clouds of gas and dust seen in absorption against the diffuse background of emission in the plane of our galaxy. Combining an extensive catalogue we have constructed of these clouds seen in absorption and the HiGAL survey of dust emission from the Galactic plane carried out by the Herschel satellite, we can identify the coldest, densest regions in molecular clouds. It is in these regions which the earliest stages of the formation of stellar clusters and massive stars are found. This project will involve obtaining and analysing millimetre and submillimetre wavelength observations of the gas and dust in these cold, dense regions to study the initial conditions which give rise to the formation of stellar clusters, particular those containing massive stars. | ||
Very High-Frequency Observations of Masers
|
Dr Malcolm Gray | |
|
A new generation of radio interferometers, such as
e-MERLIN and the JVLA, has correlators that are highly
flexible in the arrangement of the frequency channels,
of which there are typically tens of thousands. These
instruments have the capability to observe spectral lines
with a resolution as fine as 1Hz, or slightly better. In
the case of maser lines, such resolution offers the
possibility of investigating fundamentals of maser physics.
Do astrophysical masers have radiation statistics that
depart from the gaussian form that holds for thermal
radiation, for example? In the case of highly-evolved giant stars, the high resolution may be used to detect correlated frequency shifts between a number of separate maser features, enabling us to detect the passage of acoustic and MHD waves through the circumstellar envelope: a form of circumstellar seismology that has not been previously attempted. | ||
The Physical Nature of Masing Objects
|
Dr Malcolm Gray | |
|
Astrophysical masers are generated in a variety of
sources, varying in scale from comets in our own Solar
System, to kiloparsec scale zones in the cores of certain
active galaxies. A common feature of most maser sources is
that the emitting regions are observed as a set of discrete
features, some of which are resolved at VLBI resolution, that
are distributed across all, or only part, of a much larger
source region. The purpose of the project is to attempt to determine, through analysis of observational data and computer modelling, what the physical nature of the maser features is. There could be several answers, depending on the type of source. Are comets the hosts of masers in star-forming regions, as they are in our Solar System, for example? What is it that makes the gas in maser features able to generate maser radiation, whilst presumably similar gas near to them apparently cannot? | ||
Variability of OH 1612-MHz Masers in Mira Variables
|
Dr Malcolm Gray | |
| These masers are understood to be radiatively pumped by 35- and particularly 53-micron radiation, much of which is emitted by dust in the inner regions of the envelope. The amount of radiation emitted follows the pulsational cycle of the star, with a period of typically a year. The 1612-MHz emitting shell has a radius of several light-weeks, so we see the response of the maser to the stellar cycle from the blue-shifted side of the envelope, the closer to us, first in any given stellar period. We expect a roughly sinusoidal variation in the ratio of the intensity of the blue maser peak to that of the red, but instead, we see a sharp cusp in some objects at the blue-dominated part of the cycle. This project aims to understand this asymmetry in terms of the behaviour of the dust shell, using a combination of time-series observational data from the star WX Psc, and computer modelling. | ||
Mapping the southern Milky
|
Prof Albert Zijlstra | |
| The stars and nebulae in our own galaxy are surprisingly difficult to study. The Milky Way covers a very large area of sky, and surveys are still very incomplete. Large areas are affected by interstellar dust, dimming and hiding the distant regions. The central regions are extremely crowded. Complete surveys of the southern Milky Way have only recently started, using telescopes in Chile: a survey in H-alpha, searching for planetary nebulae, HII regions, and emission-line stars, and a near-infrared survey searching for variable stars. This PhD project will use these surveys to study the late stages of stellar evolution. Stars at the end of their lives eject much of their mass back into space, enriched with nuclear fusion products such as carbon and nitrogen. These ejecta drive much of the evolution of the galaxy. The ejecta are briefly visible as a planetary nebula. We will use the on-going surveys to discover the complete planetary nebula population, as well as the stars which eject them. The project will determine the planetary nebulae population, and study their shaping and their evolution. The project may involve an extended stay in Sydney, Australia. | ||
| Technology |
Spectral Line surveys for The Lovell Telescope
|
Prof Richard Davis (contact: rjd@jb.man.ac.uk) |
|
The Lovell Telescope was built in 1957 and is now largely used for Pulsar Astronomy where the Radio Frequency Interference (RFI) is mitigated by the pulse nature of the astronomy and also for MERLIN and VLBI where the use of interferometers mitigates the Interference. The presence of RFI and the great cost of very large spectrometers and the pursuance of pulars and interferometer observations has sadly left the Lovell telescope devoid of a state of the art spectral line system even though we have a four beam two polarisation receiver for the telescope. Two things have now changed this situation: very large spectrometers are now feasible for tens of Ks rather than millions of Ks using the latest hardware and firmware enabling mitigation of RFI which can test such ideas for the SKA and also giving excellent spectral resolution for the astronomy and secondly, there is now great interest in using the telescope for spectral lines particularly around the HI neutral Hydrogen frequency of 1420 MHz. This is of interest for two reasons:
The most important tool for studying the Universe on the largest scales, has been detailed measurements of the Cosmic Microwave Background (CMB) radiation. The success of future CMB experiments lies in the understanding and removal of foreground emission from our own Galaxy. RRLs are required for foreground subtraction of the Cosmic Microwave Background. This is particularly timely in these days of Planck. The early CMB experiments were not sufficiently sensitive to be troubled by the foregrounds. With each generation of instrument the foregrounds become more and more of a problem. We need to separate the synchrotron and free-free anomalous dust and vibrational dust to enable these sensitive observation of the CMB. We have mapped the radio recombination lines around 21cm with the Parkes radio telescope. We use 166,167 168 alpha all in the 64 MHz bandwidth of 1420MHz of HI. We have made maps of the diffuse emission from these RRLs. This has been achieved in the latitude range of +/- 4 degrees and with all the longitudes viewable from Parkes. We now wish to complete this in the North with the Lovell telescope. This will then enable subtraction of the free-free emission all along the galactic plane where the dust obscuration is such a problem. With modern correlators and software processing it is possible to mitigate for RFI for these spectral lines. Developments in astronomy have led us to wish to develop spectral line work for the Lovell telescope for which it was originally designed. The telescope itself was largely upgraded in 2001 and works extremely well at L-Band and C-Band. Due to the radio environment it has been left with rather poor instrumentation for spectral lines with pulsars and interferometry dominating the observing time. Thus new developments in technology and astronomy now make it extremely desirable and indeed technically possible to build a sophisticated spectral line back-end for this iconic telescope. It emerges that a suitable correlator/spectrometer does not exist for the L-band multibeam. We have 8 signals to process: 4 beams in 2 polarisation. We propose a similar bandwidth of 64 MHz with a channel spacing of 12kHz. Thus we need 5000 channels for each signal making a total of 40,000 channels. This is sufficient resolution to measure the RRLs noted above and with so many channels it should be possible to remove the RFI. In discussions it emerges that we could use the Roach Ibob Caspar system, which has been developed for SKA and for CBASS albeit with a much smaller number of channels. The software is more developed and easier to program than other RTSG systems. This will give the Lovell telescope a state of the art spectral system. This could be very useful to SKA as a pathfinder of this novel technology. Also with these enormous number of frequency channels we can mitigate RFI which of course is very important for the JBO site. This fits in very well with the guidelines for the Paul Instrument fund. These RRL lines are very narrow and we should be able to extract them with such a sophisticated system. The PhD project would involve development of the spectrometer system for the Lovell. This will either involve our own system, a National Instruments system from the MSc course or even use of the pulsar backend system depending on funding. The student would then go on to survey both on and off the galactic plane for RRLs. Further studies may involve more wide band observations for redshifted hydrogen where mitigation of interference would be developed towards HI detections. I have established the condition of the L-Band multi beam and its LO and 8 downverters. Also the filters and further amplifiers have been rescued. Help from JBCA, hopefully funded as I say, with getting the Caspar output into a computer at JBO for data acquisition. There are 8 signal paths down the telescope unless they come down digitally and are multiplexed | ||
Galactic studies for CMB foregrounds
|
Prof Richard Davis, Prof R.D.Davies and Dr R.A.Watson (contact: rjd@jb.man.ac.uk) |
|
|
The upcoming new instrument for such studies is QUIJOTE in polarization and
total power. It's frequencies are 10, 15 and 30GHz which are ideally suited
to the study of the Galactic synchrotron, free-free and anomalous dust
foregrounds. We are interested in both the diffuse contributions and the
contributions from specific sources. The QUIJOTE instrument is ideal for
this as it can be used in two modes: both by large scale scanning by
rotating at an angle tipped out of the zenith; and for targeted observations
it can perform small raster scans. The large scale scanning is similar to
the previous COSMOSOMAS experiment for which R.A.Watson has experience. The
student will initially be involved in commissioning and observational tools.
Since Planck only observes down to 30GHz, observations at these lower
frequencies will be essential for unravelling the foregrounds as preparatory
work. The student will also use data from surveys (VSA, Infrared, Radio
continuum, H-alpha, molecular line) to produce templates of the different
galactic emission mechanisms and spectra for individual sources. Galactic
polarization contribution must be clearly identified and removed before
B-modes can be measured. Probably the strongest polarization signals will
be from the synchrotron foreground.-polarization as a function of frequency
by comparison with WMAP at higher frequencies and 1.4 and 5 GHz at lower
frequencies. Essentially unknown is the polarization of the spinning dust.
(the major component at 20 GHz). These data will be highly relevant to
Planck Galactic projects at radio frequencies 30-100 GHz.
TASKS:
| ||
Low Noise Amplifiers for Radio Astronomy
|
Prof Gary Fuller (JBCA), Dr D. George (E&EE) | |
| Maximising the science which can be done with radio telescopes such the Actacama Large Millimeter/Submillimeter Array (ALMA), the largest telescope which has ever been built, and the Square Kilometre Array (SKA) requires high performance receiver systems. A central element of these receivers is their low noise amplifiers (LNA) which determines many of a receiver's fundamental operating parameters. This project will involve the design, simulation, implementation, testing and optimisation of LNAs for radio astronomy applications. There will also be the opportunity to look at the science requirements which define the required receiver and LNA performance for any particular application. There will be a particular emphasis on LNAs for SKA and, at much higher frequencies, on ALMA and other millimetre/submillimetre telescopes. Some of this project may be carried out in collaboration with a group at the California Institute of Technology (Caltech) in Pasadena, California and may require visits to CalTech. This is a joint project between the the Jodrell Bank Centre for Astrophysics and the School of Electrical and Electronic Engineering. | ||
