PhD projects

Supervisors: Michael Garrett and Simon Garrington

Contact: Michael Garrett

Active and Passive Satellite Observations with e-MERLIN

Space Situational Awareness (SSA) is now becoming an increasingly urgent aspect of Space Sustainability with the proliferation of low-Earth orbit (LEO) satellites for global internet provision and increased space debris populations. At the same time, the protection of important national assets in space, especially in geostationary orbit (GEO) is becoming more important. A related area is the study of Unidentified Anomalous Phenomena (UAP) with organisations like NASA and Project Galileo tasked with understanding their nature and origins, and their impact on national security and air traffic management.

Active satellites can be tracked using various telemetry methods and almost all objects in space (depending on size) can be tracked using radar and/or optical techniques.

Radar observations have the advantage of providing additional data on distance and velocity and are usually made using the same antenna to transmit and receive (monostatic). Because radar sensitivity scales with D4 tracking objects at GEO is much more challenging. Using large radio telescopes as the receivers in a bistatic configuration has significant advantages: large collecting area, highly sensitive and continually operating receivers, and the possibility to calibrate using astronomical sources. Initial experiments have already demonstrated the potential of this approach using transmitters at MIT (US) and FHR (Germany) and receiving antennas in the UK, Netherlands and Italy. In the UK, we have used antennas of the e-MERLIN array which comprises 7 large radio telescopes, including the 76-m at Jodrell Bank Observatory, and detected GEO satellites using both the MIT and TIRA transmitters. These observations include coherent processing to form range-Doppler 'maps' of clusters of satellites and to show the micro-Doppler signatures of tumbling space debris, such as rocket bodies. This Doppler signature can be inverted (using a range of techniques) to form high-resolution images (< 1m) of space debris in mid-Earth orbit (20,000km).

This project would build on this initial demonstration to use e-MERLIN as an array, combining the received signals from multiple telescopes to provide improved position and velocity measurements and to extend the observations to a wider range of targets. In particular it will exploit the capability of the e-MERLIN network to make synchronised and coherent measurements between antennas separated by up to 220km. The work may include: co-ordinating observations between transmitters in US and Germany with e-MERLIN (and potentially other European radio telescopes) ; simulating and processing radar data to derive ranges and velocities; synthesising data from multiple antennas; developing observing strategies to combine astronomical and radar observations to improve accuracy, coherence time and sensitivity and placing the results in a precise frame of reference; investigating novel cross-correlation techniques to augment current radar processing strategies; applying these techniques to passive observations of transmitting satellites and passive radar techniques using opportunistic transmissions. The techniques developed here could also be applied to studies of UAP and SETI (Search for Extraterrestrial Intelligence).

Supervisory Team: Prof. Gary Fuller and Dr Rowan Smith (St Andrews)

Contact: Gary Fuller

Project description: ALMAGAL: The ALMA Study of High Mass Protocluster Formation in the Milky Way

Understanding the formation of massive stars is central to wide range of astrophysics, from the star formation history of the Universe to the physical and chemical evolution of galaxies and the origin of blackholes, pulsars and gamma ray bursts. ALMAGAL is an ALMA Large Programme to observe 1000 young, high mass regions to study the formation and evolution of high mass stars and their associated stellar clusters. This project will involve the analysis of the ALMAGAL observations, and observations from related ALMA projects, to study the properties of the sources detected, the dynamics of the regions and their environments, and the evolutionary status of the protostars. ALMAGAL is large international collaboration and there may be opportunities to spend time working at some of the partner institutions. There will also be opportunities to take part in, and potentially, lead follow-up observations of some of the sources studied with ALMAGAL. The results of the analysis of the ALMAGAL observations will be compared with numerical simulations of massive star formation to help constrain the initial conditions required to form the most massive stars.

Supervisory team: Dr Patrick Weltevrede and Dr Mike Keith

Contact: Patrick Weltevrede

Project description: Characterizing the dynamic magnetospheres of neutron stars

Radio pulsars are highly magnetised neutron stars which rotate very rapidly: up to 100s of times per second. During each rotation, the radio emission beamed along the magnetic poles sweeps across the Earth and can be detected by very sensitive radio telescopes as a regular sequence of pulses. The rotation of the neutron stars can be extremely stable which makes them very accurate clocks allowing tests of the general theory of relativity.

However, for most pulsars the individual pulses of the observed sequence vary greatly in shape, intensity and polarization. These variations are caused by largely unknown physical processes in the magnetosphere of these stars. In some cases these variations happen in a coordinated fashion, which are known as drifting subpulses, indicative of regular dynamical changes in the magnetosphere.

In this project you will explore observational data from the "1000 Pulsar Array" project on the MeerKAT telescope in South Africa (a pre-cursor of the SKA: the Square Kilometre Array which will be the largest telescope in the world). This rich data-set has exquisite quality observations for many pulsars yet to be analysed in any detail. In this project you will characterize this variability seen in the pulse shapes and their polarization, and explore the implications for magnetospheric theories.

Where possible, we will supplement this data with observations from the Parkes radio telescope in Australia (a great instrument which has discovered more pulsars than any other radio telescope in the world) and the FAST radio telescope in China (largest single-dish telescope in the world).

Supervisory Team: Prof. Jens Chluba

Contact: Jens Chluba

Project description: CMB Spectral distortion anisotropies as a novel probe of cosmology

Spectral distortions of the cosmic microwave background (CMB) - tiny departure of the CMB energy spectrum from that of an equilibrium blackbody distribution - have now been recognized as one of the important future probes in cosmology and particle physics. While very challenging to observe, multiple experimental activities have started in the cosmology community with the big goal to improve the long-standing limits by COBE/FIRAS from the 1990s by orders of magnitudes. In addition to the average distortion signals in the CMB monopole spectrum, it has now been highlighted that anisotropic spectral distortions can be directly measured with existing and upcoming experiments (e.g., Planck, Litebird, The Simons Observatory, CMB-S4, the SKA). This directly links distortion science to studies of the CMB temperature and polarization anisotropies, and allows us to constrain new physics related to primordial black holes, primordial magnetic fields, axions, cosmic strings and textures as well as primordial non-Gaussianity.

In this project, you will work on the existing cosmological thermalization code CosmoTherm to develop novel tools for predicting and analysing spectral distortions signals (both average and anisotropic) in light of future CMB missions and experiments. This will identify novel methods for studying early-universe and particle physics in regimes that otherwise remain inaccessible. You bring a keen interest in theoretical physics / cosmology and experience with various modern coding languages (e.g., C++ and Python). The specifics of the project are open and multiple exciting possibilities are available, depending on the student's inclinations and strengths.

Supervisor: Dr Phil Bull

Contact: Dr Phil Bull

Project description: Commissioning the RHINO 21cm global signal experiment prototype at Jodrell Bank

Early in the Universe's history, before the first stars and galaxies had formed, the only significantly detectable EM radiation came from neutral hydrogen, which has a spin-flip transition deep in the radio part of the spectrum, at a rest-frame wavelength of 21cm. As galaxies began to switch on, the neutral hydrogen was heated and eventually re-ionised. By charting the brightness temperature of the 21cm line over time, we can learn about the magnitude and timing of these early heating processes, and thus learn about the very first stars and galaxies via their impact on their local environment.

The 21cm line is redshifted according to when in cosmic history its emission took place. To probe the time before the reionisation of the Universe, we must observe frequencies in the 70 - 100 MHz range, corresponding to emission from less than a billion years after the Big Bang. Observing this radiation is difficult however; it is faint, while other radio emission processes (such as Galactic synchrotron) occur nearby and can be several orders of magnitude brighter. Radio interference from human activity is also problematic in this part of the spectrum, e.g. FM radio. Instruments designed to observe the 21cm "global" signal in this range (its average over the whole sky) must therefore be calibrated extremely accurately, in order to make it possible for these spurious sources of emission to be subtracted from the data to uncover the 21cm signal itself.

In this project, you will work on designing and commissioning a new 21cm global signal experiment called RHINO, which currently exists as a scaled-down prototype at Jodrell Bank. The main RHINO telescope will be an extremely large (~15m high) horn antenna, which has excellent rejection of many of the systematic effects mentioned above, but will require a lot of infrastructure to build. The prototype is much more manageable however, at only ~3m in height, and can observe at ~350 MHz. The aim of this project is to demonstrate successful science observing with the prototype. This will require developing or refining some components of the receiver hardware, developing a statistics-based calibration pipeline, and observing and subsequently analysing seasons of data from the prototype telescope. The results of this project will then feed into development of the full-sized antenna. (Note: Existing knowledge of electronics/RF engineering is not necessary for this project.)

Supervisor: Ben Stappers

Contact: Ben Stappers

Project description: Discovering and Studying Pulsars and Fast Transients with SKA precursors: MeerKAT and LOFAR 2.0.

Pulsars and Fast transients represent some of the most extreme objects in the Universe. Pulsars are rapidly rotating neutron stars which have exceptionally strong magnetic fields. They have applications ranging from studying the extremes of matter through to their use as Galactic scale gravitational wave detectors. Recently we have discovered that there is a new population of very slowly rotating pulsars which challenge our ideas of how the evolve and how they generate their radio emission. Fast radio transients is a growing area of research and are epitomised by Fast Radio Bursts (FRBs), but their appear to be other manifestations too. FRBs are currently one of the most exciting and mysterious sources in astronomy. They are millisecond-long bursts of radio emission which are coming from sources that are distributed throughout the Universe: seen in our near neighbour galaxies and all the way to at least redshift 2. This combination of a burst of radio emission and large distances mean that they are excellent probes of the intervening medium and so can be used to investigate questions about the location and nature of the missing baryons and the material around, and within, galaxies.

While many hundreds of these sources are now known, the origin is still unclear. Some FRBs are known to repeat, but apparently not all do. So is there more than one type? Proposed progenitors range from highly magnetised neutron stars to the merger of neutron stars. In this project you would be part of the LOFAR 2.0 and MeerTRAP teams which will use these precursors to the largest radio telescope every built, the Square Kilometre Array to find and study new pulsars and fast transients. These projects probe very different regions of the expected parameter space for pulsars and fast transients and so are nicely complementary. You would be involved in the search for these sources, studying their emission properties and also looking at the population.

Supervisor: Prof. Christopher Conselice

Contact: Christopher Conselice

Project description: Discovery and Study of the First Galaxies and Stars with the James Webb Space Telescope

Since its launch in late-2021 the James Webb Space Telescope has started a revolution in our understanding of the first galaxies and stars formed within 500 million years after the Big Bang. This update to the Hubble Space Telescope will observe for the first time the birth of galaxies in the universe.  We will also observe some of the earliest stars when they explode as supernova and those seen as gravitationally lensed objects. I am co-leading a JWST guaranteed time observations (GTO) team who will obtain some of the earliest data from JWST for this project, in which these first galaxies and stars will be located and studied.

The student working on this project will lead the discovery of the first galaxies, and studying their properties including their masses, sizes, structures, and merger histories. We are currently obtaining ancillary data with the Hubble Space Telescope and the Very Large Telescope (VLT) in Chile. The student working on this project will take on a leadership role in investigating the stellar populations, ages, structures, and star formation rates of the first galaxies and stars using JWST imaging and spectroscopy. These observations will be interpreted in terms of theories of galaxies formation to test and exclude different ideas for how the first generations of galaxies and star formed.

Supervisors: Clive Dickinson, Stuart Harper, Vasu Shaw, Paddy Leahy, Jens Chubla

Contact: Clive Dickinson

Project description: Galactic radio emission – understanding our Galaxy for future cosmology missions

JBCA has been at the forefront of studying diffuse Galactic radio emission since the very first days of radio astronomy. We've mapped the entire sky at low angular resolution with several "low" radio frequencies (< 5 GHz) and "high" radio frequencies (30-900 GHz) with the Planck space mission. However, we still do not have a full understanding of Galactic emission across the radio/microwave bands. There are many unanswered questions, including what causes the large radio loops that cover large fractions of the sky or the halo bubbles near the Galactic centre, what is the form of dust/molecules that is responsible for anomalous microwave emission – is it due to spinning dust grains? New polarization observations also reveal a very ordered Galactic magnetic field, both locally and across the Galaxy, but a detailed Galactic model is still missing.

In addition to Galactic science, detailed measurements of the Cosmic Microwave Background (CMB) provide the strongest constraints on cosmological parameters. Future CMB polarization missions are aiming to constrain primordial B modes, caused by a background of gravitational waves, which would be a smoking gun signature that inflation happened in the first fractions of a second of the Universe. However, one of the major challenges is in quantifying and removing "foreground" emission, which for B modes, is at least an order of magnitude brighter than the cosmological signal we're trying to detect!

JBCA is involved in several world-leading experiments that are both trying to measure CMB B-modes and quantify the contaminating foreground emission, including:

• C-Band All-Sky Survey – 5 GHz all-sky survey to map synchrotron intensity and polarized emission with high sensitivity and fidelity, to provide a foreground template for future CMB missions. C-BASS is likely to be the key low frequency data for future missions, as it is at the ideal frequency and is able to map the sky with high sensitivity with minimal systematic errors. We have completed the northern survey and the southern survey will be starting in the near future.
• COMAP Galactic Plane Survey – 26-34 GHz survey of the northern Galactic plane with the COMAP instrument at 5 arcmin resolution to study Galactic emission, particularly AME/spinning dust near 30 GHz. Manchester is leading this sub-project for the COMAP collaboration. The survey is well underway and is expected to be completed ~2025.
• LiteBIRD – next generation Japanese-led space mission to provide the ultimate limits on inflationary B-modes. LiteBIRD is the successor to the immensely successful Planck space mission, to be launched ~2030, and could potentially provide the best limits on inflationary B-modes on large scales (r<0.001). As part of LiteBIRD UK, U. Manchester is responsible for analysis pipelines for component separation and systematic error mitigation.

We are looking for a PhD student that is interested in radio data analysis techniques, with the potential to work on both low level (e.g. improving calibration of C-BASS/COMAP data, data reduction etc.) and high level (e.g. CMB component separation, Galactic science) analyses. The exact nature of the PhD will depend on the experience and interests of the student. Much of the work will be aimed at preparation for the LiteBIRD space mission, including simulations of foregrounds and potential systematic effects. Some of the work may also be applicable to the Simons Observatory (SO) project that Manchester is also involved in.

Supervisor: Dr. Laura Wolz

Contact: Laura Wolz

Project description: HI Intensity Mapping with MeerKAT

A key goal of cosmology is to understand the accelerated expansion of the Universe, believed to be driven by a force called Dark Energy. Mapping the distribution of galaxies throughout the Universe’s lifetime can measure the expansion history and help us understand the nature of Dark Energy. Historically, cosmologists have successfully used the optical emission of stars located in galaxies to map the cosmic web over time. In the past decade, a new method called intensity mapping has emerged which uses the radio emission of gas (specifically the highly abundant Neutral Hydrogen gas) to trace the galaxy distribution. The future Square Kilometre Array (SKA) and its pre-cursor MeerKAT are enormous radio telescope arrays, capable of higher sensitivities and spatial resolution than any existing radio instrument. Intensity mapping is a unique probe, as it can be observed using the SKA as a single dish array, as well as in interferometric mode which gives much higher spatial resolution in the data. Both datasets are essential if we aim to acquire a complete understanding of how hydrogen traces dark matter and how gas and galaxies evolved with cosmic time.

PhD projects are available to work on the on-going MeerKAT data analysis, both in Single Dish as well as in interferometric mode, as well as the simulation of data including instrumental effects. Topics for exploration include optimisation of the HI and cosmology constraints by combining information from both data types, improvement of the data reduction pipelines as well as preparations and forecasts for SKA observations. Most project work will be computationally and the student will work within the teams of MeerKAT and SKA intensity mapping. Some background reading can be found here https://arxiv.org/pdf/2010.07985.pdf and https://arxiv.org/pdf/2206.01579.pdf.

Supervisors: Prof. Robert Beswick and Dr David Williams-Baldwin

Contact: Dr David Williams-Baldwin

Project description: Long term studies of star formation in M82

Understanding the star formation rates of nearby galaxies is important for both galaxy evolution but also our knowledge of stellar physics. In an ideal world, star formation rates can be estimated from optical light received from a galaxy. However, this is complicated as the optical light from an active galactic nucleus must be taken into account, and large amounts of dust and gas can extinct or absorb optical light, biasing estimates. High-resolution radio observations provide the perfect probe of these different classes of object as radio waves are unaffected by this extinction and absorption. The radio waveband is especially useful as it traces both the thermal emission from HII regions of young massive stars, but also the non-thermal emission from the shells of supernova remnants. Radio observations of star forming galaxies are therefore an excellent independent probe of star formation rates which can be used to calibrate other star formation correlations.

The nearby supernova factory M82 has been intensely studied by e-MERLIN and other radio interferometers over the last 4 decades, owing to the high optical absorption which has prevented study of the supernovae, HII regions and exotic transient objects in this galaxy in optical bands. This project will concentrate on radio datasets of M82 over several decades to continue the long-term monitoring of this source and explore new areas such as widefield imaging now that higher performance computers are available. This project can take several different routes depending on the candidates preferred areas and interests, including e-MERLIN data analysis of similar star forming galaxies in the LeMMINGs survey, 10s mas resolution European VLBI Network data to resolve individual supernova remnants or more in depth coding to search for transients over the course of the last 40 year's worth of observations. The candidate should be able to use python and have an interest in radio astronomy on stellar objects.

Supervisor: Prof. Keith Grainge

Contact: Prof. Keith Grainge

Project description: The MeerKLASS UHF Radio Source Survey

MeerKLASS is a project that has already been awarded hundreds of hours on observing time on the MeerKAT telescope, one of the precursor instruments for the Square Kilometre Array, based in South Africa. One of the data products from MeerKLASS is a survey in the UHF (550 – 1050 MHz) band for extragalactic radio sources. This survey will be both wide is survey area (several hundred square degrees); high angular resolution (~10 arc-seconds); and high sensitivity flux sensitivity. In addition to the extremely valuable legacy survey that this will provide, the same patch of sky will be observed multiple times on a variety of different timescales, allowing for a search for time variable sources. The study of these transient phenomena allows study of: cosmic explosions from fast radio bursts, supernovae and gamma ray bursters; and accretion onto black holes, neutron stars and white dwarves.

The student will join a team of two academic staff and three postdocs working on MeerKLASS at JBCA. The project will involve collaboration with a team centred at Munich, who are doing complementary survey work at L-band (1000 – 1700 MHz), allowing the possibility for investigations across a broad spectral window. In addition, the wider MeerKLASS team will use the survey catalogues for the removal of foreground sources in the search for the signatures of redshifted neutral hydrogen, so there is the possibility of becoming involved in this work, seeking to map out the evolution of large scale structure in the Universe and constrain cosmology.

Supervisors: Dr Michael Keith and Dr Patrick Weltevrede

Contacts: Dr Michael Keith and Dr Patrick Weltevrede

Project description: Mining the Jodrell Bank Pulsar Timing Data Archive

The pulsar group at Jodrell Bank has been studying pulsars for over 50 years, and regularly observes around 800 pulsars. These datasets usually stretch back to the discovery of the pulsar, and are therefore the most complete records of pulsar arrival times in the world. Using these data we can track the rotation of the pulsar, and in most cases this means that we unambiguously know when every rotation of the pulsar occurred since it was first observed.

These data are a valuable tool for understanding the complex physics that governs the rotation of pulsars. In particular, it is of great interest to understand how pulsar rotation evolves over time, and how we can characterise and understand the rotational instabilities in the pulsar. We also can use the data to track the position of pulsars over time, and hence get some understanding of the velocity distribution of the pulsars, which we can use to understand the processes leading to the birth of neutron stars.

In this project you will be tasked with extracting deeper understanding of pulsars by applying modern data science techniques such as Bayesian Analysis and Gaussian Processes to the Jodrell Bank pulsar timing database.

Supervisory Team: Prof. Gary Fuller and Prof. Philippa Browning

Contact: Gary Fuller

Project description: Modelling time domain radio emission in the circumstellar regions of protostars

Understand how a forming star acquires its final mass is a fundamental issue for a building a comprehensive model of star formation.  The time-dependent and transient nature of the process of mass accretion from the circumstellar disk to the protostar is difficult to study and poorly understood. However, this process can be diagnosed through variable emission it produces. Recently, we have developed new idealised models (Waterfall et al Mon Not Roy Astr Soc 483, 917, 2019; Waterfall et al. Mon Not Roy Astr Soc 496, 271, 2020) of this phenomenon in T-Tauri stars, in which magnetic large loops interconnecting the star and the accretion disk are filled with non-thermal electrons due to magnetic reconnection which emitting at radio wavelengths.

The aim of the current project will be to develop more sophisticated and realistic models of this process and predict its radio emission. This will be done using numerical resistive magnetohydrodynamic simulations of protostars, which will predict the energy release due to magnetic reconnection as the stellar magnetic field interacts with the disk.  Then, the gyrosynchrotron radio emission due to electrons accelerated by the reconnection – similarly to solar flares – will be calculated, modelling both the intensity and polarization properties as a function of frequency as the accretion event progresses.

Comparison of the results of these models with observations will provide some of the first insights on this final stage of accretion on to protostars. The results will provide important constraints on the design the first large scale radio surveys of star forming regions with the world’s largest radio telescope, the Square Kilometre Array (SKA) and there may be the opportunity to be involved in the comparison of the model predictions and observations made with current radio telescopes.

Supervisor: Prof. Scott Kay

Contact: Scott Kay

Project description: Next generation hydrodynamic simulations of galaxy clusters

Galaxy clusters host the most massive galaxies in the Universe, with stellar masses up to one trillion times the mass of the Sun. These galaxies are surrounded by huge reservoirs of hot, X-ray emitting plasma, with temperatures over 10 million Kelvin. A puzzling observation, however, is that this gas is not cooling down and forming new stars at the expected rate - why does star formation shut down in massive galaxies? One, currently favoured, answer is that the gas is being kept hot by an active galactic nucleus (AGN) through the emission of powerful jets of radio-bright relativistic plasma. The AGN, powered by accretion on to a super-massive black hole, is energetically capable of counteracting the radiative losses in the X-ray gas and can even drive some of the gas out of the system altogether.

Modern hydrodynamic simulations of galaxy clusters attempt to include the effects of this so-called AGN feedback process and can successfully model the shut-down of star formation in brightest cluster galaxies, while producing black holes with observationally-reasonable masses. However, these simulations currently struggle to reproduce the X-ray thermal properties of the gas, predicting material that tends to be too hot and diffuse in the cluster core. Such a discrepancy is likely the result of current models not capturing all the essential physics but may also be due to insufficient numerical resolution.

In this PhD project, the student will join ongoing collaborative efforts to develop a new generation of cluster simulations with improved resolution and physics modelling using the SWIFT hydrodynamics code (swift.dur.ac.uk). They will work on science projects involving the analysis of new simulation data as well as have the opportunity to help develop and test new simulation models. The student will join the Virgo consortium and use the DiRAC high performance computing facility (dirac.ac.uk).

Supervisory Team: Prof. Michael Brown, Prof. Richard Battye, Prof. Jens Chluba, Prof. Lucio Piccirillo

Contact: Michael Brown, Richard Battye, Jens Chluba, Lucio Piccirillo

Project description: Probing the Early Universe with Simons Observatory

Simons Observatory (SO) is a next-generation Cosmic Microwave Background (CMB) telescope to be located in Chile. Its primary objective is to make high fidelity images of the Cosmic Microwave Background which will allow constraints on fundamental physics. The University of Manchester leads a recently-announced major UK contribution to SO (termed SO:UK) which will have a major impact on SO’s ability to pursue this headline science goal. The UK team will provide: (i) two additional state-of-the-art telescopes for SO, (ii) a UK-based data centre for processing the large data volumes and (iii) a program of algorithm development aimed at turning the raw data from the ~80,000 detectors into higher-level data products and scientific results. The JBCA at The University of Manchester hosts the data centre and is delivering one of the two SO:UK telescopes. We are also playing a major role in the pipeline development work. As part of our group you will have the opportunity to get involved with this state-of-the-art CMB experiment in multiple areas including contributing to the instrument development, developing data processing algorithms and in the scientific exploitation and interpretation of the data. There are three PhD projects available to work with the SO team at the JBCA which will be between 10 and 15 scientists. Each will become part of the team taking a general interest in the overall project, but will also have specific responsibilities. Projects B and C should expect real SO data on the timescale of the PhD, while the delivery of the SO:UK SATs involved in project A is due during the timescale of the PhD.

* Project A: (Piccirillo and Brown)

This will be a technical project involving the build of the two SO:UK telescopes. Our group is in charge of the build and operation of a state-of-the-art telescopes dedicated to the observations of the CMB. It will be a vital part of the most sensitive experiment ever built in experimental cosmology. The student will play a major role in the assembly, testing and operations of the telescope first in the testing site at Jodrell Bank Observatory and then at the observing site in Atacama (Chile).

* Project B: Constraining primordial gravitational waves (Brown and Battye)

One of SO's primary goals is to detect a very specific pattern in the polarisation of the CMB radiation (termed “B-modes”) which will provide a unique observational window into the very early Universe and physics at GUT-scale energies. These B-modes can be created by primordial gravitational waves, but also by other non-standard physics such as birefringence. These signals are typically very weak and it will require exquisite control of systematics. The project will involve some work on the data pipeline working with the data centre staff , development of sophisticated mathematical algorithms to remove systematic effects and playing a role in the international SO working group on B-mode science.

* Project C: Using the Sunyaev-Zeldovich effect to constrain fundamental physics (Battye and Chluba)

The SZ effect is the inverse Compton scattering of CMB photons by the gas inside galaxy clusters along the line of sight. It has a unique spectral signature and it has been used to constrain cosmological parameters such as the matter density, the amplitude of perturbations and others including the properties of dark energy and neutrino masses. This is done using observables such as the number of clusters a function of redshift and the power spectrum fo the Compton y-parameter. The JBCA plays a significant role in the SZ working group. The objective of the PhD will be to work on the modelling of the SZ effect, which involves numerical simulations, modelling the observations and ultimately using the results to constrain cosmological models and the underlying astrophysics of clusters.

Supervisory Team: Dr. Paddy Leahy (primary), Prof. Anna Scaife (secondary)

Contact: Paddy Leahy

Project description: Probing the Galactic magnetic field with POSSUM

Our Galaxy’s magnetic field plays an important role in the interstellar medium, sometimes dominating the local dynamics and rarely negligible. It helps regulate star formation and accelerates some particles to relativistic energy, forming cosmic rays. These processes are not fully understood, and nor is the structure of the magnetic field, which is often described as turbulent although some organized patterns can also be discerned. There are many observational tracers of the interstellar field, but they all have severe limitations, and so we must make progress by using observational clues to guide theoretical and computational modelling.

One of the most important magnetic tracers is Faraday rotation: the plane of polarization of radio waves change with wavelength, at a rate proportional to the integral the magnetic field component along the line of sight, weighted by the free electron density. This can be relatively easily assessed using extragalactic radio sources, which give us the integrated Faraday rotation along the sight line through the Milky Way. Mapping this across the sky gives a weighted 2D projection of the 3D magnetic pattern. The quality of this information is about to be vastly increased by the Polarization Sky Survey of the Universe’s Magnetism (POSSUM), an international project to measure the polarization of radio sources across most of the sky at 800-1088 MHz, using the Australian SKA Pathfinder (ASKAP), which will give a 10-fold increase in sampling of the Faraday rotation pattern.  In addition to extragalactic sources, POSSUM will detect polarization from synchrotron emission in the interstellar medium, which in principle gives more direct information about the 3D field structure, although there are challenging instrumental issues that have to be overcome.

The aim of this PhD project is to study the statistical structure of the Faraday rotation and the underlying magnetic field. The primary observational input will be the POSSUM Faraday results: about one quarter of the sky will have been observed in time to use,  including fields close to the Galactic plane with a long sight-line through the disk, and at high latitude where we are looking just through the local layer of the Galaxy. You will draw on other observational results as needed, for instance single-dish observations of the Galactic synchrotron emission at short wavelengths, where the polarization traces the field component in the sky plane. You will interpret your results using theories ranging from toy models that can be run on a laptop to the outputs of massive full-disk magneto-hydro-dynamic simulations being run by Rowan Smith and collaborators.

Supervisor: Dr Michael Keith

Contact: Dr Michael Keith 

Project description: Pulsar Timing Arrays for the detection of Nanohertz Gravitational Waves

In June 2023 the European Pulsar Timing Array (EPTA) and collaborators around the world announced the first evidence for a background of ultra-low frequency gravitational waves from super-massive black hole binaries in the centres of distant galaxies:

• Astronomers find first evidence for new class of gravitational waves which could unveil origin of the Universe

A pulsar timing array makes use of high precision (<1 microsecond) timing measurements of the rotation of millisecond pulsars to form a galaxy-scale gravitational wave detector. We can directly detect the gravitational waves through the quadrupolar correlated variations in the arrival times of pulses from the pulsars.

The Lovell Telescope at Jodrell Bank has been observing these pulsars for decades, and these observations are a key part of the EPTA and International Pulsar Timing Array datasets. More recently new telescopes have also started contributing highly sensitive observations of additional pulsars. In Manchester we are continuing to provide data from the Lovell Telescopes, as well as from the MeerKAT telescope in South Africa, an important precursor telescope for the upcoming international Square Kilometre Array Telescope. We are also involved in studying the pulsars themselves, including the effort to better understand the 'foreground' pulsar noise which can mask the signal from the gravitational wave background.

This project will involve working with the observations from the Lovell Telescope and MeerKAT for Pulsar Timing Array work, and developing new data analysis techniques, with potential to explore ways to exploit recent developments in machine learning. The overall goal is to better understand the signals that we see in the pulsar timing array data, leading to a clear and unambiguous detection of the gravitational wave background.

Supervisory Team: Prof. Gary Fuller and Prof. Danielle George (Department of Electrical and Electronic Engineering)

Contact: Gary Fuller

Project description:  Pushing the Noise Limit: Low Noise Amplifiers for Radio Telescopes

Low noise amplifiers (LNAs) are critical components of receivers for radio telescopes. They offer a number of important advantages over competing technologies such as operating at 20K rather than 4K as well as being better suited for use in large scale imaging array receivers. Recent advances in technology have allowed the development of LNAs which operate at much higher frequencies than previously possible.

This is an opportunity to join the Advanced Radio Instrumentation Group in the Departments of Physics and Astronomy and Electrical and Electronic Engineering. 

There are four possible areas of research:

• The designing and testing high performance, wide bandwidth, LNAs at frequencies of up to 300 GHz, and beyond, for use in both single pixel and array receivers on the world’s biggest telescopes.
• The design and construction of receivers for current radio telescopes using new generation, high performance LNAs.
• New processes and materials for transistors for future, high performance generations of LNAs.
• Computer-aided LNA design optimisation.

In each of these areas there is the possibility of placements at various collaborating international institutions, including ESO in Germany and Bologna in Italy.  

Supervisor: Rene Breton

Contact: Rene Breton

Project description: Relativistic irradiation in spider binary pulsars

Binary pulsars are formidable physics laboratories, allowing us to investigate fundamental processes due to their extreme nature (density, magnetic field and gravitational field). This is only possible as they offer proxies to measure their physical parameters via multi-wavelength observations. Of particular importance are the pulsar binaries nicknamed after the deadly spiders ‘black widows’ and 'redbacks', which contain a rapidly rotating millisecond pulsar that gradually destroys a low-mass companion. Current observations demonstrate that these particular systems harbour some of the most rapidly spinning and massive pulsars known to us.

The PhD student will contribute to several projects led by the supervisor’s "Spiders Team" which aim to find and characterise new spiders to understand the underlying physical mechanisms to their remarkable properties. On the observational side, the Spiders Team is involved with multiple pulsar searching efforts conducted at optical and radio wavelengths such as surveys conducted by the TRAPUM collaboration with the MeerKAT telescope. In-depth studies of known systems across the electromagnetic spectrum -- in particular in the radio and optical regime -- are then performed in order to feed into models that enable us to determine system parameters such as orbital inclination, masses, and more. This work uses advanced data science techniques such as Bayesian statistics, forward modelling tools such as MCMC and nested sampling, and machine learning. On the theoretical side, numerical modelling of the binary evolution and stellar structure of the companion is another active area of investigation which offers insights about the extreme interactions which led the pulsar to gradually destroy its companion.

The overarching goal of the PhD project will be to shed light on the impact that the pulsar's relativistic irradiation has on the companion's evolution. The student will look into interaction mechanisms for heat to be deposited into a stellar atmosphere (using photons, lepton or ions as the energy carriers) and their effects on the internal structure of such a star. They will then build self-consistent evolutionary tracks that incorporate the pulsar's irradiation feedback to model the population of sources and compare with observations. Opportunities to get involved with other projects conducted by the Spiders Team highlighted above will also be possible.

Reading list on the general spider pulsar binary topic:

• Spider Pulsars 101

Supervisor: Prof. Richard Battye

Contact: Richard Battye

Project description: Searching for axions using neutron stars

Axions are one of the leading dark matter candidates and can be converted into photons in the magnetosphere of neutron stars. This can lead to a spectral line signature in the radio/mm waveband. In recent times we have developed techniques to predict the signal expected and have been applying these to observations made by the JVLA and Lovell Telescopes.

The aim of the project - which would likely involve collaboration with scientists in Louvain and Munich as well the JBCA pulsar observers - would be to refine these predictions, involving modelling axion electrodynamics in the magnetosphere, and compare to the most update to date observations. It will require a range of theoretical, numerical and data analysis related skills. At its most optimistic it could lead the detection of the dark matter axions, but more likely stringent upper bounds on their coupling to photons. It could also lead onto a study of the theoretical models for the production of axions.

Supervisor: Dr. Eamonn Kerins

Contact: Eamonn Kerins

Project description: Space-based exoplanet detection with microlensing

Microlensing is proving to be the most capable method to find cool low-mass planets, including planets around the most common types of star, and planetary architectures that most resemble that of our own solar system. The demographics of these planets is also crucial for testing planet formation theories.

In the next few years NASA will launch the Nancy Grace Roman Space Telescope (Roman) which will undertake a dedicated exoplanet microlensing survey. With a field of view 100 times greater than the Hubble Space Telescope and a data rate more than 20 times that of JWST, Roman will revolutionize our understanding of exoplanet demographics. The ESA Euclid mission may also undertake an exoplanet microlensing survey.

Manchester has developed the Galactic microlensing simulation framework that underpins the design of potential surveys for both Roman and Euclid. A PhD project is available to further develop this simulation framework to enable detailed optimization and analysis work that will be required for both missions.

The project will be computational in nature, both using existing codes and developing new ones. We have a dedicated 64-core AMD Threadripper machine dedicated to our exoplanet work. The exoplanet group working with Kerins currently comprises 5 PhD students and one MSc student. It is expected that this project will involve working closely with colleagues based in France and the US.

Supervisory Team: Dr Paddy Leahy (primary), Dr Emmanuel Bempong-Manful (co-supervisor)

Contact: Paddy Leahy

Project description: Testing models of relativistic jets with e-MERLIN

Many of the issues in understanding structure formation and black-hole growth are thought to be resolved by suitably-tuned feedback of energy and momentum from AGN activity – from dense to diffuse phases of matter.  Relativistic plasma jets of radio-loud AGNs are particularly thought to be responsible for the production of the most energetic photons and hadrons in the observable Universe, thereby playing a key role in this feedback cycle. However, the physics driving the observed jet structure in these cosmic outflows remains an open question. To resolve them we need to quantify the mass, momentum and energy inputs from jets and to work out how they interact with their environment.

Here at Manchester we are leading an ambitious global effort  (The e-MERLIN Jets Legacy programme) to resolve these and other key questions in extragalactic jet physics. The programme has been mapping a number of powerful radio galaxies and quasars, allowing us to study for example the detailed structure of magnetic field in relativistic jets (the synchrotron radiation polarisation) and in the foreground gas (via Faraday rotation). Deep LOFAR observations have also been acquired for the programme, providing us with the unique opportunity to probe the dynamics and energetics of relativistic jets over broad frequencies.

The goal of this PhD project will be to utilize these new radio observations to map the jet structure of some well known powerful radio galaxies in order to test the relativistic beaming model in jets. The student will join the e-MERLIN Jets Legacy collaboration and become a part of the LOFAR-VLBI Working Group. Depending on their interests, the project could be extended into a multiwavelength campaign with complementary observations at optical and X-ray wavebands, and/or perform numerical MHD simulations to model the jet kinematics and compare theory with observations.

Supervisor: Dr Rebecca Bowler

Contact: Dr Rebecca Bowler

Project description: The evolution of galaxies in the early universe with the next generation of telescopes

At the cutting-edge of Astronomy research is the study of the formation and evolution of the first galaxies. Through breakthrough observations in the past 30 years it has been possible to identify galaxies from when the universe was less than 400 million years old. These galaxies have unusual properties compared to the local universe, showing low chemical enrichment and dust obscuration, and irregular morphologies. This project aims to exploit the new Vera Rubin Observatory (VRO) and Euclid space-mission to discover and analyse galaxies at very high-redshifts (probing the first few billion years). The goal of the project is to understand when and how the most star-forming galaxies formed in the Universe. The student will become an expert in the selection of high-redshift galaxies from multi-band photometry. They will then use the resulting samples to constrain the evolution of the number density of these sources (via the luminosity function). There is considerable flexibility in the direction of the project in later years, and the student would be encouraged to apply for follow-up data (e.g. with JWST, ALMA) as well as exploit archival data where available. At the end of the project the student would be in an excellent position to continue working with these next generation facilities.

VRO is an 8.4m diameter optical telescope that is being built in Chile. As well as surveying the entire southern sky it will also provide four deep fields which will contain many hundreds of thousands of distant galaxies:

• Vera C. Rubin Observatory

Euclid is an optical and near-infrared space mission. It is primarily a cosmology mission but it will discover many thousands of high-redshift galaxies. As Euclid has a near-infrared camera (like Hubble) it will be able to discover very distant galaxies (z = 7-10).

• The Euclid Blog

Supervisory Team: Dr Paddy Leahy, Prof Ian Browne, Prof Peter Wilkinson

Contact: Paddy Leahy

Project description: Is there a new radio background? The L-Band All-Sky Survey (L-BASS)

The aim of the L-BASS project is to map the intensity of the radio sky at ~1.4 GHz with unprecedented absolute accuracy (0.1K) – ten times better than achieved by Penzias and Wilson in their discovery of the cosmic microwave background radiation. There are several reasons to do this, the most exciting being that it should settle a current astrophysical puzzle about the reality of excess all-sky low frequency emission of unknown origin (the “ARCADE-2 controversy”). Such an excess might also help account for another recent controversial result which is the claimed detection of strong absorption arising in atomic hydrogen situated at a redshift of 17 (the “EDGES result”). In addition our sky map will have impact on Galactic astrophysics and our knowledge of the Cosmic Microwave Background.

During the PhD project the student will produce and interpret the first sky maps with the L-BASS telescope system which is situated at Jodrell Bank Observatory. The system, which is based on two large horn antennas, is now up and running. Commissioning observations are in progress. This PhD project involves a mixture of hands-on work to optimize the calibration of the system, making precisely calibrated observations and writing software for data analysis followed by the astrophysical interpretation of the results. To achieve the required accuracy (0.1K) requires particularly careful calibration using a cryogenically cooled reference load of known physical temperature; the assembly and testing of this cryogenic calibration load will take place during the next two years and form a significant part of the project. In two years, the plan is to move the instrument to Tenerife, a site which enable us to map two thirds of the whole sky.

Supervisory Team: Prof. Gary Fuller and Dr Rowan Smith (St Andrews)

Contact: Gary Fuller

Project description: The Role of Magnetic Fields in the Formation of Massive Stars

Magnetic fields are ubiquitous in the interstellar medium but their detailed role in the formation of stars is as yet unclear. In the dense star forming regions of molecular clouds the magnetic field can be traced through observations of the polarized continuum emission from dust grains which align with the magnetic field. However, to understand how magnetic fields affect the evolution of the gas, observations of the magnetic field must be combined with observations of the cold, molecular gas in the regions. This project will study the impact of the magnetic fields as gas flows from parcsec-scale clumps down to individual star forming cores and protostars. It will involve observations of polarization emission from dust and molecular lines to study the magnetic field and molecular gas covering a wide range of size scales in star forming regions. Part of the project will be developing new methods to compare the polarization and line observations with the results of state-of-the-art magneto-hydrodynamics simulations.  This work will be carried out in part as part of the follow-up of ALMAGAL, the ALMA large programme studying the formation and evolution of high mass stars and the ERC Synergy project ECOGAL.

Supervisor: Prof. Richard Battye

Contact: Richard Battye

Project description: Topological defects at the electroweak phase transition

Topological defects can be formed at cosmological phase transitions where the vacuum manifold has non-trivial homotopy.  The objective of this project is to explore the possibility that topological defects might be formed at the electroweak phase transition in extensions of the Standard Model of particle physics. We have bene studying the so-called two Higgs-Doublet model (2HDM) which is one of the most popular extension with Prof Apostolos Pilaftsis in the Manchester Particle Physics group.

The project will involve further developing the work often using large-scale computing resources based in the Manchester and elsewhere in the UK. It will also develop the picture of cosmological evolution of such defects, and also consider how such a defect might be produced in a particle accelerator such as the LHC.

Supervisors: Scott Kay, Jens Chluba

Contact: Scott Kay

Tracing cosmic baryons with the Sunyaev-Zel’dovich effect

The Sunyaev-Zel’dovich (SZ) effect is the inverse-Compton scattering of CMB photons off free electrons, leading to a distortion in the CMB blackbody spectrum. At present, it is routinely used to measure the pressure profiles of hot (T~10^7K) gas in nearby, resolved galaxy clusters. On larger scales, it can also be used to find the missing baryons in the cosmic web. Future instruments at millimetre/sub-millimetre wavelengths will allow SZ observations to be made with even more accuracy, opening the door to additional measurements such as the temperature and velocity of the warm and hot cosmic gas, in clusters and beyond. In this project, the student will use a combination of the latest hydrodynamical simulations (see e.g. the FLAMINGO project) and theoretical modelling tools to make predictions for future observations of these SZ signals. These can then be used to make quantitative predictions for the thermal and kinematic properties of the intergalactic and intracluster gas, and how these relate to the underlying dark matter distribution. Such models can also be used to inform requirements for future CMB instrumentation.

Supervisor: Dr. Phil Bull

Contact: Phil Bull

Project description: Unveiling Cosmic Dawn with the Hydrogen Epoch of Reionization Array

Cosmic Dawn - the time when the first stars and galaxies switched on - remains shrouded in mystery. While challenging to observe using optical and near-infrared telescopes due to the rareness and obscuration of bright sources, a series of radio telescopes (like HERA, the Hydrogen Epoch of Reionization Array, in South Africa) are being constructed that have the sensitivity to detect the presence of large amounts of neutral hydrogen during this epoch, via the 21cm emission line. This will allow us to map the neutral gas surrounding the first bright sources and understand how rapidly they reionised the Universe.

HERA is a large interferometric array that will have up to 350 receiving elements when fully completed. It is being built in stages, and has already collected several seasons of data in a smaller configuration with between 50-100 receivers. Recent analyses of early seasons have produced the best upper limits on the power spectrum of 21cm fluctuations from the Cosmic Dawn and Epoch of Reionisation to date (see https://arxiv.org/abs/2108.02263), with significantly larger volumes of data well on the way.

In this project, you will develop and hone a set of advanced statistical analysis tools to recover the 21cm power spectrum from the available HERA data despite the presence of much brighter contamination ("radio foregrounds") and systematic effects due to the complexity of the instrument. These tools are based on a variety of techniques for high-dimensional Bayesian inference, a type of machine learning. Through this project, you will develop a mix of skills, including some analytic theoretical work on statistics, hands-on data analysis with a large, cutting-edge astronomical dataset, and high-performance computing, which may include some GPU programming. The student will be able to choose which of these areas to put more emphasis on.