Below are some of the MSc(R) projects for this coming year. We will try to keep this list updated, particularly on the lead up to the beginning of the first semester (17 September 2018, which is the induction week). However, we encourage prospective MSc(R) students to speak with as many of our academic staff, as early as possible, to find out what we do and to see if there are possible MSc(R) projects available - this list is unlikely to be comprehensive and research projects can quickly become out-of-date. Note that supervisors and projects should be decided within the first 1-2 weeks of the first semester and they should inform the MSc(R) course director, Neal Jackson).
A Northern-sky survey at 15 GHz
Supervisors: Keith Grainge, Anna Scaife
Surveys of substantial areas of the sky at high radio frequencies are challenging and few have been performed. As a result our knowledge of the high frequency radio source population is poor. The Arcminute MicroKelvin Imager Small Array (AMI-SA) is now conducting a legacy survey of the complete Northern hemisphere at 15 GHz. This project will calibrate and image the AMI-SA drift scan data and combine the different scans into a continuous map. This map will be searched for sources, a catalogue compiled and a weighted differential source count calculated. Identified sources will be followed up and imaged with the AMI Large Array to give angular resolution comparable to the NVSS survey. Comparing the AMI catalogue with NVSS will allow calculation of the radio spectral index distribution between 1.4 and 15 GHz and identification of any currently undiscovered inverted spectrum sources.
Are the hosts of spiral DRAGNs true spirals?
Supervisors: Dr. Minnie Mao and Dr. Patrick Leahy
In the nearby Universe, DRAGNs (Double Radio sources associated with AGNs) are almost invariably hosted by giant elliptical galaxies. The existence of spiral DRAGNs defies our current understanding of galaxy formation. Nonetheless, there are now a handful of confirmed examples of spiral DRAGNs. Spiral galaxies are known to host large amounts of neutral hydrogen (HI) in a rotationally stable disk. Conversely, the host galaxies of double-lobed radio sources may be void of HI emission, or contain tumultuous HI disks with large velocity dispersions. The student will be studying the hosts of spiral DRAGNs to determine their HI content. Are the HI properties of Spiral DRAGNs similar to those of normal spirals?
We have recently obtained Very Large Array (VLA) spectral-line observations of three spiral DRAGNs. There will be the opportunity to reduce, image, and analyse VLA data to determine the HI properties of spiral DRAGN hosts. The student will also be studying the multi-wavelength properties of the spiral DRAGN hosts, using both new and archival data. Specifically we are interested in the morphology, star-formation rate, and environment. The student will use the AIPS/CASA data reduction packages and will also be required to write simple scripts. Some prior data reduction experience may be useful.
Crab delayed spin-ups
Supervisor: Prof. Ben Stappers
With their high densities, ultra-strong magnetic fields and rapid rotation rates, neutron stars offer a window into extreme-environment astrophysics not attainable elsewhere in the Universe. As radio pulsars, they are well-known as remarkably stable celestial clocks, yet many young pulsars undergo 'glitch' events in which their rotation rates abruptly increase. Following the increase, the pulsar may then relax back towards the previous rotation rate over timescales ranging from several hours to many months. These rare and unpredictable events are thought to occur as a result of a rapid angular momentum exchange between the neutron star's crust and a superfluid interior. Observations of glitches therefore, offer critical insights into the exotic nature of the interior and provide key inputs for crust-fluid coupling models. However, the nature of the initial rise remains challenging to observe and characterise due its rapid occurrence compared with the regularity with which most pulsars are typically monitored.
The Crab pulsar (PSR B0531+21) has undergone 25 glitches since its discovery in 1968. At Jodrell Bank we have monitored the Crab pulsar for many hours every day since 1984. Recently we observed and measured the largest glitch ever recorded in this source and due to our frequent, high quality observations of the Crab, we were able to resolve ~7% of the total spin-up over a timescale of ~2 days. This is the third observation of a ‘delayed’ spin-up associated with a large glitch in the Crab pulsar and this has not been observed in any other source. In this project we will take advantage of the 45 years of Crab pulsar rotation data we have accumulated at Jodrell Bank to revisit all previous Crab pulsar glitches in order to constrain the nature of the spin-ups as well as search for delayed spin-ups that have so far remained unidentified. Where possible, we will also investigate the relationship between glitch rise times and amplitudes and determine whether delayed spin-ups are a feature of all or only the largest Crab pulsar glitches. The student will gain knowledge of radio data analysis and pulsar timing methodology, and will have the opportunity to write-up their findings for submission to a peer-reviewed journal
Molecular gas in ULIRG-to-QSO transition objects
Supervisors: Dr. Robert Beswick & Dr. Jeff Wagg (SKA Organisation)
Since the early surveys of FIR continuum emission in ultraluminous infared galaxies with IRAS, it has been believed that some galaxies go through a heavilly dust obscured starburst phase before emerging as an optically luminous quasar. These have termed the ULIRG-to-QSO transition objects. The initial burst of star-formation is thought to be the product of a gas-rich merger. However, recent years have seen the emergence of a new picture, where gas-poor galaxies containing an active galactic nucleus, can be `refueled' by mergers with gas-rich galaxies. Sensitive interferometers observing at mm-wavelengths allow us to isolate the source of the molecular gas in these systems previously classified as ULIRG-to-QSO transition objects.
We have completed an interferometer survey of CO line emission in a sample of ULIRG-to-QSO transition objects using the Combined Array for Research in Millimeter-wave Astronomy (CARMA). All of these sources benefit from high sensitivity imaging from the Hubble Space Telescope. A student would work on the CARMA data in order to learn the fundamentals of mm-wavelength interferometry and produce maps of the mm-wavelength CO line emission. It is expected that a research publication would be produced as a result of this analysis.
Neutron star formation through electron-capture supernovae
Supervisor: Dr. Rene Breton
The classical formation channel of a neutron star is the core-collapse of a massive star as a supernova. In recent years, there has been tantalising evidence from the properties of some pulsar binaries that a fraction of the neutron star population might form via electron capture supernovae. In this scenario, a 7-10 Msun star building a degenerate ONeMg core collapses as the capture of electrons by magnesium causes a sudden lost of hydrostatic pressure. Such an event would also leave behind a neutron star but its mass would likely be lower than via the traditional channel. In addition the electron-capture scenario may impart a much smaller kick to the neutron star, which could explain why some double neutron star systems are in circular rather than eccentric orbits.
This project will explore the formation of neutron stars through electron capture supernovae. Using stellar evolution codes, such as MESA, the student will investigate the conditions leading to an electron capture event and their effects on the resulting neutron star, such as its mass and spatial velocity. The candidate will also look at how the evolution in a binary system may increase/decrease the odds of a star becoming a neutron star through this channel, which has implications, among other things, for survival rate of binary systems and the retention of neutron stars in globular clusters. The project has broad implications for our understanding of binary evolution, the pulsar population, and the calculation of the rate of double neutron star mergers which are a primary source of gravitational waves to be observed with LIGO.
Horns and polarizers for the L-Band All-Sky Survey (L-BASS)
Supervisors: Prof. Ian Browne, Prof. Peter Wilkinson, Co-supervisor: Prof. Clive Dickinson
L-BASS is a project to make a high precision map of the sky at a frequency around 1420MHz (L-band). There are both technical and astrophysical motivations for the project. The technical one is that for L-BASS, and for a related project BINGO, large horns with very low sidelobes and excellent polarization characteristics need to be constructed. Fabrication of such horns using conventional methods would be impossibly expensive. However, a new technique has been pioneered at Jodrell Bank in which the horns are constructed out of sheets of inexpensive insulation foam stacked to produce the required shape. A half-sized horn has already been made and shown to have excellent performance. The two horns being constructed for L-BASS will be the largest made using this technique and, if these horns live up to expectations, the same fabrication technique will be used for 50+ horns for BINGO, thus saving the project approximately $1 million. In terms of astrophysics, the L-BASS absolutely calibrated map of the sky is required to improve the separation of Galactic foreground emission from that of the cosmic Microwave Background as well as for Galactic science. In addition, our map will test the intriguing claim (Seiffert et al.) that there is an unexplained new component to the radio emission at these low frequencies.
The project is to characterize the properties of two large horn antennas and then help mount them so that an absolutely calibrated map of the sky can be made. The electrical properties of the horns will be measured in the laboratory and then their polar diagrams will be measured using a test range at Jodrell Bank. In parallel, waveguide-polarizers will be built which convert the output from the horns to opposite hands of circular polarization, something that is required because the emission from the sky is linearly polarized. By observing in circular polarization the received signal does not depend on the orientation of the antenna. The polarizers will need to be tuned in the lab using a vector network analyser. Finally the horns, polarizers and an existing radio receiver will be integrated and mounted on a prepared site at Jodrell Bank Observatory and the overall performance of the system characterized.
Heating the solar corona: 3D numerical magnetohydrodynamic simulations and 1D modelling of the turbulent dynamo
Supervisor: Prof. Philippa Browning
A major unsolved problem in astrophysics 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. Much research concerns modelling the dissipation of magnetic energy through the process of magnetic reconnection. There are two potential projects in this area. One project will involve running numerical simulations using the LARE3D code, which numerically solves the equations of magnetohydrodynamics, and analysing the results. This will build on recent work showing that reconnection can be triggered by the onset of the kink instability in twisted coronal loops, exploring a range of magnetic field configurations and exploring the energy release. The second project will use a simplified analytical model of the effects of turbulent reconnection, building on one-dimensional models widely used for laboratory plasmas in which the turbulence is parameterised as a 'dynamo' electric field. These models will be extended to solar coronal loops, requiring some analytical calculations and simple numerical modelling (solution of ordinary differential equations).
High energy particles in solar flares
Supervisor: Prof. Philippa Browning
Solar flares are dramatic releases of stored magnetic energy, emitting electromagnetic radiation from radio to hard X-rays or gamma rays. Large numbers of non-thermal ions and electrons are produced, but the origin of these high-energy particles is not understood. A promising theory is that particles are accelerated by the strong electric fields associated with reconnection of the magnetic fieldlines. This can be studied using a "test particle" approach, in which charged particle motion is calculated in electromagnetic fields representative of reconnection. A project is available to use test particle models to study the generation of high energy particles in solar flares - this will involve adapting existing computer codes, as well as some programming and analytical calculations.
Studying Large-Scale Structure using Intensity Mapping of CO at High Redshifts
Supervisor: Prof. Clive Dickinson and Dr. Stuart Harper
Intensity mapping is a recently proposed method of efficiently mapping the emission of single spectral lines across cosmological volumes. Proposals for intensity mapping have been made using many different species such as atomic HI, CII, Lyman-N1, CO, amongst others. All the lines can be used to study the large-scale structures of galaxies and clusters, which trace the evolution of the baryonic matter density and cosmic expansion. As CO is predominantly found within the dark, cold cores of star forming nebulae, CO predominantly traces star forming galaxies, which means it can also be used to measure the star formation history of the Universe.
The CO intensity mapping experiment called COMAP is planning to use the intensity mapping technique to map out a large volume of the Universe, starting in the next 1 to 2 years. COMAP will probe the redshift range of 2 < z < 3, which is during the epoch of peak of cosmic star formation. However, measuring the cosmological CO signal is expected to be challenging due to mixing of the signal with bright Galactic emission, turbulence within the atmosphere, instabilities of the instrumentation and the interaction of optical systems with the sky and surrounding environment. To overcome these challenges has required building a detailed end-to-end simulation of the COMAP experiment.
The student will be involved in COMAP experiment, which is an international collaboration between Manchester, Caltech, JPL, Stanford, and Oslo. The project offers an opportunity to become involved in an exciting field of cosmological research that is still in its infancy. The thrust of the project will be to run simulations of the COMAP observations that will be critical in determining the specifications of the instrumentation and designing data analysis methods for recovering the cosmological CO signal. As such, the project offers a lot freedom in the topic or topics the student wishes to pursue, from instrumentation, atmospheric science, Galactic emission, cosmology, and advanced data analysis methods; depending on interest and experience of the student.
Probing of the Magnetic Field in Star Forming Regions with SKA using CH
Supervisor: Prof. Gary Fuller
Magnetic fields can play an important role in the formation of stars. This project will investigate the potential of SKA> observations of CH as a probe of the magnetic field in star forming regions. CH has two groups of transitions which can be observed with SKA. The lower frequency transitions, which are at a frequency around 700MHz, are potentially very good probes of the magnetic field. However there has been very little observational or modelling work done on these transitions. This project will investigate the nature of these CH transitions and through modelling, and potentially exploratory observations, how SKA1 and eventually SKA2 will be able to use these transitions to study the magnetic field in dense gas in star forming regions.
SiO Maser Movies
Supervisor: Dr. Malcolm Gray
SiO masers form in broken ring patterns around their host stars, which are mostly long-period variables of Mira and semi-regular variable type. These stars are pulsational variables, and the maser zone is disrupted by periodic shock waves that propagate outwards from the photosphere. The maser zone also coincides approximately with the condensation zone of alumina dust that helps convert pulsational motion into a steady outflow at larger radii. Hydrodynamic solutions for the atmosphere, coupled with maser pumping models, can be combined to provide a theoretical counterpart to a time-sequence of VLBI observations, improving our understanding of the establishment of mass-loss. It should be possible to make a movie of the motions of a number of maser objects at intervals of approximately one month over several pulsational periods.
Contaminating Weak Lensing Cosmology with Active Galactic Nuclei
Supervisors: Dr. Ian Harrison and Prof. Michael Brown
Measuring the weak lensing distortion of the shapes of millions of galaxies across the sky is an excellent way to learn about cosmological parameters and probe the different physical models of Dark Energy. Most weak lensing studies (such as the Dark Energy Survey) are conducted with optical telescopes, but recently new work has begun to focus on the prospect of weak lensing with radio telescopes such as e-MERLIN and the Square Kilometre Array (SKA). Doing weak lensing at radio wavelengths has a number of advantages but also a number of new challenges, one of which is the presence of different types of sources of the sample of galaxies used. The shapes of ordinary star-forming galaxies should be (relatively) easy to model with simple profiles with minimal error, but the shapes of Active Galactic Nuclei (AGN) in the radio are expected to be much more complex. The presence of AGN mistakenly included in the weak lensing sample can cause an error known as 'model bias' which directly affects the cosmological results. The aim of this MSc project will be to investigate how bad this model bias will be for different levels of AGN contamination and how it could be avoided.
The student will perform mostly computational work, simulating images of AGN and fitting simple models to their shapes. The student will gain knowledge in the general areas of cosmology, statistics and radio astronomy. The project has a well-defined outline and could easily lead to a published peer-reviewed journal article.
Supervisor: Dr. Neal Jackson
Gravitational lenses are systems in which a background object is multiply imaged by the action of the gravitational field of a foreground galaxy. Gravitational lensing is important because it allows us magnified views of distant objects in the Universe, and also because it allows us to investigate mass distributions in galaxies independent of their light emission. We are currently involved in a number of projects with major radio facilities (e-MERLIN and LOFAR) and planning for future surveys, including Euclid. Accordingly, there are a number of areas in which students could become involved:
- We have LOFAR observations of a cluster, A2626, with interesting radio structure and unusual radio arcs. This is likely to be an interesting exercise in cluster physics, but it is just possible that it may have something to do with lensing. The project will involve reduction and analysis of these LOFAR data (co-supervised with Prof. Ian Browne).
- We are currently conducting a survey, called LOBOS, to find long-baseline calibrators for the international baselines of the LOFAR array. This is a crucial project in making sure that these telescopes work properly and deliver observations. The project will involve helping with the LOBOS survey, and possibly extending this to providing calibration methods for other observations. (co-supervised by Dr. Amit Tagore).
- We are involved in a science working group of Euclid which is investigating the use of Euclid-discovered gravitational lenses for the study of galaxy evolution. The student will assist with the simulation of the scientific output from such a survey.
A first look at the Galactic magnetic field with the C-Band All-Sky Survey (C-BASS)
Supervisor: Dr. Paddy Leahy
The C-Band All Sky Survey is a major project to map the Galactic and extragalactic synchrotron emission, and particularly its polarization, across the whole sky. It will be used both to help understand the Galaxy's magnetic field, and to correct Cosmic Microwave Background polarization observations for the foreground synchrotron emission. We are using two telescopes, one in Owens Valley, California, and one in the Karoo desert, South Africa. We have now produced science quality maps of intensity and polarization with the Northern instrument, which allows us for the first time to study the synchrotron polarization across the Northern sky.
This polarization depends on the Galactic magnetic field. The fractional polarization is fixed by the field tangling in the interstellar medium, while the field direction is given by the polarization angles. Residual Faraday Rotation at 5 GHz can be fixed by comparison with surveys at higher and lower frequencies such as WMAP and the DRAO Penticton survey, which gives the line-of-sight component of the magnetic field. The student will analyse all these maps to constrain models of the interstellar magnetic field.
All-sky map-making with Single Dish Radio Telescopes
Supervisor: Dr. Paddy Leahy
There are many projects in progress to map the radio sky at various different frequencies (from 300 MHz to 857 GHz) by scanning the sky with single dish telescopes. Examples include the WMAP and Planck cosmic microwave background satellites, C-BASS, and the GMIMS polarization survey which uses Penticton, Canada, and Parkes in Australia.
In all these surveys we wish to make a map of the sky, which comes down to finding the brightness of the radio emission (in several Stokes parameters) at each pixel in some convenient tiling of the celestial sphere. The problem is that the data is not collected by pointing at each pixel centre, but by scanning the telescope in some pattern with no particular relation to the sky pixelization. Since the telescope sees the sky convolved with its point-spread function (the "beam", as radio astronomers say), this gives full information about the sky provided that gaps between neighbouring measurements are smaller than half the beam width. The simplest way to treat such data is to bin each measurement into the nearest pixel, and this is what all current surveys do. But in many ways this is very sub-optimal and it would be better to interpolate the data onto the sky pixel grid. There are two problems to be solved: (i) computationally efficient interpolation onto the pixelised sphere (all standard interpolation routines work on a flat cartesian grid) and (ii) determination of the optimum interpolation function. The latter depends on the beam shape and also on the scientific purpose intended for the sky map. One example of the latter is to compensate for highly elliptial beams, such as some of those on WMAP and Planck, which otherwise make the sky maps difficult to interpret, especially in polarization.
This MSc project will produce and test an interpolation map-maker using the high-level IDL language, which will function as a prototype for an advanced map-maker for the Planck and C-BASS projects.
The ages of extra-solar planets
Supervisors: Prof. Albert Zijlstra & Dr. Iain McDonald
How has the frequency of planets changed through the Universe's history, and how do individual planetary systems evolve over time? These questions are important in understanding for how long the Galaxy has been able support life. This project provides answers, by determining a homogeneous set of ages for planets beyond our solar system. The Gaia Space Telescope is returning distances from millions of stars, and we have recently published the temperatures and luminosities for about 1.5 million of these. Several hundred of them are known exoplanet hosts. The MSc project will focus on this targetted set, placing these stars more exactly on the Hertzsprung--Russell diagram, and using the latest stellar evolution codes to determine how old each planet-hosting star is. Comparing this to the star-formation history of the solar neighbourhood will help tell us whether planets are a relatively new phenomenon, or have been present since the Galaxy's early formation, and whether unusual system architectures (e.g. hot-Jupiter systems) are more commonly created early or late in a star's evolution.
Observation and modelling of nova explosions
Supervisor: Prof. T.J. O'Brien
Novae are interacting binary stars in which a white dwarf accretes matter from a companion star. A thermonuclear explosion on the surface of the white dwarf ejects the matter, causing a significant brightening across the spectrum from radio waves to gamma rays. Our group and international collaborators are involved with monitoring nova outbursts using a range of telescopes and interpreting the observations in terms of hydrodynamic models of the explosion. A number of projects are possible in this area, including reduction and analysis of radio observations (including from e-MERLIN), hydrodynamic simulations of shocks and modelling of X-ray emission. Outstanding questions relate to the geometry of the ejecta and the ultimate fate of the white dwarf, in particular whether some of these systems eventually end as supernova explosions.
SETI research with the Jodrell Bank radio telescopes.
Supervisors: Prof. T.J. O'Brien, Prof. M.A. Garrett, Dr. R. Breton (JBCA) & Dr. A. Siemion (Berkeley)
We only have one example of life in the Universe, here on Earth. Searches are ongoing on Mars and, in the near future, other solar system bodies. But we now know there are likely to be billions of habitable planets in the Milky Way alone. We may even find spectroscopic evidence of life (bio-signatures) on one of these planets in the next few decades. However, the unambiguous discovery of intelligent life probably requires the detection of techno-signatures e.g. artificial narrow-band radio signals. There are a number of ongoing SETI projects around the world searching for such signals (e.g. Breakthrough Listen), and next generation telescopes such as the Square Kilometre Array (see this review paper <http://arxiv.org/abs/1412.4867>) will have a major impact on the field.
At Jodrell Bank, SETI observations can include the analysis of (i) raw voltage data streams from single dishes or (ii) cross-correlated multi-band data from the e-MERLIN interferometer array. Students working on this project will be involved in recording data and analysing it. A full analysis will also require the students to develop software that sorts and filters the data, permitting potential SETI signals to be distinguished from local contributions e.g. man-made interference. New techniques and algorithms will be explored that take into account phenomena such as Doppler drift, e-MERLIN targeted beam-forming or the detection of low-level, broad-band SETI signals, thus expanding the region of search space that can be explored. The work will be undertaken as part of Jodrell Bank’s collaboration with the Breakthrough Listen programme (see https://breakthroughinitiatives.org/initiative/1). Students should be comfortable with handling large data sets and the development of software for large computer systems. Although we have no idea whether extra-terrestrials exist, let alone whether they are sending us messages, experience tells us that analysis of signals in a new region of parameter space may well bear fruit in other areas of astrophysics.
A superconducting parametric amplifier for the new generation of radio telescopes
Supervisors: Prof. Lucio Piccirillo, Dr. Mark McCulloch, Dr. Simon Melhuish
Parametric amplifiers are well known to have excellent low noise performances suitable for astronomical receivers. Very recently it has been proposed that the kinetic inductance of superconductors can be used as a non linear parameter to realise ultra low noise parametric amplifiers. These amplifiers have the potential to possess a large gain/bandwidth product and possibly even beat the quantum noise limit!
These amplifiers have also important applications in other fields like, for example, quantum computing.
The student will be involved in the theory of superconducting parametric amplifiers as well as in the design, realisation and testing of test amplifiers. During this work the student will learn radio-frequency design, cryogenic design and testing, low temperatures techniques (sub-K).
Direct detection of very high frequency gravitational waves
Supervisor: Prof. Lucio Piccirillo
Graviton to photon conversion is possible in the presence of a strong static magnetic field (inverse Gertsenshtein effect). The photon generated will be coherent with the original graviton. We are interested in exploring the theoretical and technical issues related to the direct detection of gravitons in the GHz to optical frequencies. The potential sources of such high frequency gravitons are at a moment very speculative: Kalutza-Klein 5D gravity and/or the inflationary period in the big bang. A prototype detector has been in operation for several months collecting useful data.
The student will be involved in the data analysis and simulations as well as in the continuation of the design studies for a more sensitive detector.
A miniature dilution refrigerator for astrophysical applications
Supervisor: Prof. Lucio Piccirillo
Bolometers are the preferred detectors of astrophysical radiation in the mm/sub-mm and far infrared. When operating in low background, bolometers need to be cooled to extremely low temperatures 300 mK to 30 mK. Below 100 mK the preferred cooling technology is based on the dilution cooling of mixture of He-3/He-4. Our group is world leading in the development of miniature dilution systems that can be operated in small cryostats suitable for operations at the focal plane of telescopes.
The student will be heavily involved in the design, realisation and testing of a fully tiltable miniature dilution refrigerator.
Development of a novel passive correlator for the next generation of radio astronomy interferometers.
Supervisor: Prof. Lucio Piccirillo
Diffraction of electromagnetic waves limits the angular resolution of radio telescopes. The larger the diameter of the telescope the better the angular resolution. Unfortunately, building larger telescope to achieve better and better resolution is very expensive: it scales roughly with the diameter to the power of 2.8. Radio interferometry allows us to achieve high resolution by combining the amplitude/phase of the electromagnetic waves coming from many small telescope. The combination is achieved by electronic correlators. Correlators are very complex electronic devices: the current limit to the number of antennas that can be correlated is of the order of few tens (the number of signals, or baselines, goes as the square of the number of antennas).
A novel passive correlator will be studied theoretically and especially experimentally. The idea to be tested consists in optically combining the amplitudes of the waves coming from each telescope in an optical "beam combiner". This system can potentially correlate hundreds of telescopes. The student will work with a team that will design, build and test a 3 x 3 quasi optical correlator working at 11 GHz. The prototype will be fielded at the Jodrell Bank Observatory from where observations of some strong radio sources will be performed.
Impact of Instrument Systematics on the Detection of the CMB B-Mode Polarisation
Supervisors: Dr. Mathieu Remazeilles and Prof. Clive Dickinson
The primordial CMB B-mode polarisation is the exclusive signature of the Big Bang gravitational waves predicted by the theories of cosmic inflation. However, it has not been yet detected. The detection of the CMB B-modes is extremely challenging for many reasons: the cosmological B-mode polarization signal is particularly faint (< 0.1 micro K), gravitational lensing by large-scale structures is causing leakage of the E-mode polarization into B-mode polarization, highly-polarized foreground emission in the late universe considerably scrambles the cosmological CMB B-mode signal, and instrument systematics (e.g beam asymmetries, missing data ) creates spurious B-mode polarization. The main goal will be to measure the the tensor-to-scalar parameter that determines the energy scale of inflation.
The project will consits in generating simulations of CMB experiments including instrumental systematics and in performing an end-to-end propagation of systematic errors to the tensor-to-scalar parameter by using a parametric Bayesian fitting method and a Gibbs sampling technique (COMMANDER component separation method). Depending of the results on the impact on the tensor-to-scalar parameter of systematic errors, we will optimize a future CMB experiment for the detection of B-modes.
Galactic Faraday Rotation with the Jansky Very Large Array
Supervisor: Dr. Anna Scaife
When the polarised radio emission from the ultra-relativistic electron population in high energy astrophysical objects passes through the magneto-ionised medium of our own Galaxy, the polarisation angle of such emission is rotated as a function of frequency - an effect known as Faraday rotation. By making observations over a range of different radio wavelengths this rotation can be used to infer the magnetic field strengths along the line of sight through the Galaxy between ourselves and the emitting object. This project will use data from the new P-band receivers on the Jansky Very Large Array (JVLA) telescope to develop a calibration strategy for measuring Faraday rotation from a bright polarised pulsar.
Radio Emission from Brightest Cluster Galaxies (BCGs) in Disturbed Galaxy Clusters
Supervisor: Dr. Anna Scaife
It has been proposed that the brightest galaxies (BCGs) in clusters of galaxies that have undergone violent merger activity are less likely to produce radio emission than their counterparts in relaxed systems. This absence has been suggested to be due to more effective gas stripping, both during and following the merger activity. This project will use archival radio data to identify the fraction of BCGs which have detectable radio emission and to correlate the radio luminosity (as well as other characteristics) of these galaxies with the global properties of their host clusters, most specifically the entropy of the intra-cluster gas, in order to determine if relationships can be established which indicate the degree of disturbance necessary to prevent radio emission being produced.
Probing the Ionosphere with the KAIRA telescope.
Supervisor: Dr. Anna Scaife
The Kilpisjärvi Atmospheric Imaging Receiver Array (KARIA) uses technology from the LOFAR array to form an independent radio telescope situated in Finnish Lapland (69°4'15''N 20°45'43''E). KAIRA monitors the Earth's ionosphere in a variety of different ways using novel techniques available due to the specialised underlying LOFAR design. One of these techniques uses the emission from pulsars - highly magnetized, rapidly rotating neutron stars that emit periodic radio bursts - to detect local temporal and spatial changes in the total electron content (TEC) of the ionosphere. To do this, KAIRA measures the amount of Faraday rotation caused by the ionosphere in the pulsar's polarized radio emission, which provides a linear measure of the line-of-sight electron density and magnetic field strength. Currently, KAIRA operates a pulsar mode only using its High Band Antennas (HBA; 120-180 MHz). In order to extend this experiment to the Low Band Antennas (LBA; 10-80 MHz) requires the individual sub-bands for the LBA to be sub-divided into narrower channels to maintain pulse coherence.
This project will design and implement a system to channelize individual sub-bands in the KAIRA-LBA using a poly-phase filter bank or other Fourier based method. This system will then be used to extend the KAIRA pulsar experiment to LBA frequencies. By including LBA frequencies, the accuracy with which Faraday rotation can be measured for these pulsars will improve significantly (Faraday rotation is function of wavelength-squared), allowing us to measure smaller changes in the ionospheric TEC content due to various space weather events. The student will have the opportunity to use KAIRA data directly to demonstrate their system.
Finding the dark gas in the Milky Way.
Supervisor: Dr. Rowan Smith and Prof. Gary Fuller
Despite the fact that the Milky Way is our home galaxy, there is still much that we do not know. In particular much of the gas that makes up our galaxy is "dark", i.e it cannot be observed using conventional methods. For example molecular hydrogen does not emit radiation at the typical temperatures found in the interstellar medium, instead its presence must be deduced from CO emission, but if the molecular gas does not have CO it cannot be observed. Alternatively if atomic hydrogen is optically thick then its true mass may be underestimated. This is especially true at the interface between cold molecular clouds, where stars like our sun form, and their hotter surroundings.
In this project we will perform mock observations of a recent high-resolution simulation of a Milky Way type galaxy. This will involve taking density, temperature and chemical abundance distributions from the numerical simulation and using a radiative transfer code to calculate the predicted emission. We will use the simulated emission maps to investigate where in the Galaxy "dark mass" might be hidden and what the implications might be for the formation of clouds of molecular gas. In particular we will make hydrogen absorption line profiles that can be compared to the THOR (the Hydrogen, OH and Recombination line) survey to test our models of how molecular clouds form. The comparison to this survey, being carried out by the Jansky Very Large Array, should allow the student to get a flavour of both theoretical and observational techniques. Some knowledge of programming would be beneficial for this project but as we will initially be using existing software and routines it is not absolutely essential.
Recombination line ratios in NGC253
Supervisors: Dr. George Bendo
ALMA has observed multiple hydrogen recombination line transitions at gigahertz frequencies within the central starburst in the nearby galaxy NGC 253. In general, these spectral lines are a superior metric for measuring star formation rate, as the spectral line emission can be directly related to the number of short-lived photoionizing stars that are present (unlike infrared or radio continuum emission) and as the spectral line emission is unaffected by dust extinction (as is the case with ultraviolet and optical hydrogen recombination line emission). However, this is dependent upon the assumption that the line emission is primarily spontaneous emission and not stimulated emission. The goal of this project is to use the ratios of the hydrogen recombination lines to test whether the emission is primarily spontaneous emission.
Unveiling the most extreme starbursts in the Universe with deep, multi-wavelength imaging
Supervisors: Dr. Alasdair Thomson, Dr. Rob Beswick
Studies of the extragalactic background light have revealed that up to half of all the star formation that has occurred throughout the history of the Universe took place in “dusty” environments, which are obscured from the view of visible-light telescopes. Interstellar dust grains absorb UV/optical starlight, and re-radiate it in the far-infrared, giving rise to a well-established relationship between the star formation rate and infrared luminosities of star-forming galaxies. The most luminous dusty galaxies (“starbursts”) formed new stars at rates >500x faster than the Milky Way today, and – though rare – are thought to have hosted up to 50% of the star formation occurring at “cosmic noon”, 10bn years ago.
Observations at ~850µm wavelength (the “submillimetre” regime) are uniquely well-placed to detect dusty starbursts, out to the farthest reaches of the Universe – however, the difficulties in tying emission observed with submillimetre telescopes to individual galaxy populations seen at other wavelenghts have long hindered our efforts to understand this important class of star-forming galaxy in detail. The aim of this MSc project will be to employ a newly-developed technique (Chen et al., 2016) to identify the counterparts to a population of submillimetre-selected galaxies (SMGs) recently identified with the James Clerk Maxwell Telescope in Hawaii, and explore their properties using cutting-edge multi-wavelength datasets. Some prior knowledge of programming and data analysis would be beneficial, but neither are essential at the outset, as it is expected that the student would develop these skills during the course of the project.
The polarization properties of radio galaxies
Supervisors: Dr. Lee Whittaker, Prof. Richard Battye and Prof. Michael Brown
Polarization information in the radio observations of distant galaxies could be extremely useful for future high precision cosmology. For example, it has been shown that there is a correlation between the direction of polarization in radio sources and the gradient of the total intensity field, and this property can be exploited to study the distribution of dark matter in the Universe, the nature of dark energy, and also to place tight constraints on a cosmological rotation signal, such as that expected from cosmic birefringence.
At present, there are various quantities that need to be known for these methods to be competitive, such as the strength of the above correlation and the dispersion in the polarization signal. This project aims to study these properties in observations of radio galaxies, thereby providing an opportunity to contribute to future cosmological studies, such as those performed using the Square Kilometre Array (SKA).