Extra seminars, which can be organised by anyone in the group separately from the colloquium series, are also included on this page for convenience.
To view a talk abstract, click on the talk title. Click again on the talk title to hide the abstract.
| Date | Speaker | Topic |
|---|
| Sep 13 |
Special Seminar
Hiroko Shinnaga
(Kagoshima University) |
Episodic mass loss of a red supergiant just before supernova explosion |
| Evolved stars experience high mass-loss rates forming thick circumstellar
envelopes (CSEs). The circumstellar material is made of the result of stellar
nucleosynthesis and, as such, plays a crucial role in the chemical evolution
of galaxies and the universe. Since asymmetric geometries of CSEs are
common, and with very complex structures for some cases, radiative pressure
from the stars can explain only a small portion of the mass- loss processes;
thus the essential driving mechanism is still unknown, particularly for high-mass stars.
We study a very bright, peculiar red supergiant VY CMa using several telescopes.
I review some recent studies of this object including the results obtained mainly
with the VLA and ALMA. If time permits, I showcase very recent results from
Japanese VLBI Exploration of Radio Astrometry (VERA) telescope and Subaru
Telescope of this source.
Reference:
Strong magnetic field generated by the extreme oxygen-rich red supergiant VY Canis Majoris
H. Shinnaga et al. PASJ 69,L10 (free access)
http://adsabs.harvard.edu/abs/2017PASJ...69L..10S
Hosts: Anita Richards and Adam Avison |
| Sep 19 |
JBCA Colloquium
Dr. Donna Rodgers-Lee
(University of Hertfordshire) |
The ionising effect of low energy stellar cosmic rays in protoplanetary disks |
| Abstract: Young low-mass stars are typically more magnetically active than our Sun making it reasonable to assume that they accelerate particles to ~GeV energies, as the Sun itself is an effective MeV accelerator. These low energy cosmic rays may prove to be an important source of ionisation for the very weakly ionised protoplanetary disks surrounding young stars.
Here, based on the assumption that young low-mass stars accelerate protons to ~GeV, we estimate the ionising effect of these low energy stellar cosmic rays in protoplanetary disks. We solve their transport equation by treating the propagation of the cosmic rays as diffusive. We find that, generally, the high column density in the inner region of the protoplanetary disk prevents the cosmic rays from significantly ionising the outer regions of the disk. We discuss further ways of investigating the ionising effect from low energy protostellar cosmic rays.
Host: Rachael Ainsworth |
| Sep 26 |
Schuster Colloquium
Prof. Leon Koopmans
(University of Groningen) |
From the Cosmic Dawn to the Epoch of Reionization: a Radio Quest for Neutral Hydrogen in the Infant Universe |
| Abstract: Detection of the redshifted 21-cm signal of neutral hydrogen from the Cosmic Dawn and Epoch of Reionization (EoR) promises a new avenue to study physical processes of early star and galaxy formation during the first billion years of the Universe. These eras form the foundation of our present-day observable universe. The quest for a detection of this 21-cm signal has been exceedingly hard with current radio telescopes, and has not yet been achieved, although steady progress is being made. I will give an overview of what can be learned from observing these early phases of the infant Universe as well as a broad overview of ongoing experiments aiming to detect this feeble signal. In particular, I will provide a status update on the
LOFAR EoR Key Science project and the challenges that it and other similar projects are facing. I will show that considerable progress has been made in the last years, but that not all challenges have yet been met. I will end by introducing several exciting new projects that we have recently started, to observe the Cosmic Dawn and the Dark Ages, and give a glimpse of future
opportunities with the SKA and HERA.
Host: Mike Garrett |
| Oct 3 |
JBCA Colloquium
Prof. Huub Rottgering
(Leiden University) |
LOFAR Surveys: a new window on the Universe |
| Abstract: The Low-Frequency Array (LOFAR) is a pan-European radio telescope whose massive data taking and processing capabilities make it an unprecedented powerful instrument for
carrying out the deepest and widest radio surveys at low radio frequencies.
Over the last years we have addressed important issues related to the analysis and calibration of the radio data so that
we can now make thermal noise limited maps at low frequencies. The resulting
wide and deep maps enable studies of a wide range of scientific topics ranging from (i) shocks in merging clusters, (ii) radio feedback processes, (iii) star formation in distant galaxies and (iv) the most distant radio galaxies, close to the epoch of deionisation.
In this talk I will first discuss our solutions to the main technical challenges. Secondly, scientific highlights will be given related to these 4 topics.
References: http://adsabs.harvard.edu/abs/2016ApJ...818..204V
http://adsabs.harvard.edu/abs/2018MNRAS.480.2733S
Host: Anna Scaife |
| Oct 10 |
JBCA Colloquium
Alessio Spurio Mancini
(University of Heidelberg) |
Constraining dark energy and modified gravity models with cosmic shear |
| Abstract: `Cosmic shear' is the weak gravitational lensing effect caused by the large-scale structure of the Universe, which bends light coming from background sources and induces correlations in the distorted shapes of galaxy images. Cosmic shear is one of the main probes to study dark energy and modified gravity models alternative to ΛCDM, capable of explaining the observed cosmic acceleration. I will show current and future constraints that can be achieved with cosmic shear on a large set of these models, the Horndeski class, which includes the vast majority of theories with one scalar field in addition to the metric.
First, I will forecast the sensitivity of future cosmic shear surveys, such as Euclid, to functions that characterise Horndeski models, showing in particular how a fully 3D analysis of the cosmic shear field, alternative to a traditional tomographic approach, can increase constraints on all cosmological parameters and in particular on Horndeski parameters and the sum of neutrino masses.
I will then show how cross-correlations of cosmic shear with other probes can constrain Horndeski theories of gravity, presenting results of a joint cosmic shear, galaxy-galaxy lensing and galaxy clustering analysis of available data from the KiDS and GAMA surveys, as well as predictions for the sensitivity achievable with future cross-correlations of Stage IV cosmic shear, galaxy clustering and Cosmic Microwave Background experiments.
Finally, I will comment on some of the numerical challenges associated to a cosmic shear analysis, how they can be tackled and how to develop a new approach to cosmological inference based on the Minkowski Functionals of the cosmic shear field.
References: http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1801.04251
http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1804.02441
http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1807.11461
Host: Sarah Briddle |
| Oct 15 |
Special Seminar
Dana Simard
(University of Toronto) |
Reconstructing complex pulsar scattering environments with global VLBI |
| Abstract: Pulsar scintillation, the variation of the observed flux of a pulsar due to multi-path propagation, allows a glimpse into the small-scale plasma structures in the interstellar medium that scatter pulsar radiation - if we can infer their properties from the observed scintillation pattern. We have developed a model of scintillation from refractive plasma sheets that makes testable predictions which can be compared with observations to investigate these plasma structures. The main challenge in testing these models is mapping the scattered flux distribution of the pulsar on the sky, and to put physical scales to the constraints we must determine the scattering geometry of the system. I will discuss our novel interferometric technique to reconstruct the scattered flux of the pulsar and solve for the scattering geometry, even if the scattering environment is complex. This allows us to expand our study of pulsar scintillation to more systems and improve our global understanding of plasma scattering, which may benefit timing of millisecond pulsars and the aid in the interpretation of spectral structure in Fast Radio Bursts.
Host: Elliott Polzin, Rene Breton |
| Oct 17 |
Schuster Colloquium
Prof. James Pinfold
(University of Alberta) |
Dirac's Dream: The Quest for the Magnetic Monopole |
| Abstract: The elusive magnetic monopole is arguably the most important particle that has yet to be discovered. We shall follow the search
for the monopole from its Victorian beginnings until today and discuss how we can continue into the future. We shall see that this quest describes a golden thread that runs through
fundamental physics from its classical beginnings, through its quantum conception, to the brave new world of Grand Unified Theory and Theories of Everything. Nevertheless, I shall consider this adventure from an experimentalist's point of view.
Hosts: Terry Wyatt |
| Oct 24 |
JBCA Colloquium
Dr. Katharine Johnston
(University of Leeds) |
Accretion discs around massive stars: the revolution with ALMA |
| Abstract: Circumstellar discs are widely known to be one of the main conduits for accretion of matter onto forming low- and intermediate-mass stars, with their structural and kinematic properties being well-characterised by numerous studies. In addition, there is growing evidence that centrifugally supported discs exist around forming OB-type stars, however a key question is how the properties of these discs compare to those around their lower-mass counterparts. In this colloquium, I will begin with a brief review of the properties of discs around low- and intermediate-mass stars, as well as the theoretical background for the existence of discs around massive stars. I will then review the observational evidence for discs around massive stars prior to ALMA, and conclude with the recent results ALMA has begun to provide in this field. In particular, I will present our ALMA Cycle 1 and 5 observations of AFGL 4176, a highly luminous (~10^5 Lsun) forming star, where transitions of CH3CN and 1.2mm dust continuum show a disc 2000AU in radius, with signatures of Keplerian rotation and spiral structure around a ~25Msun star.
Host: Rowan Smith |
| Oct 31 |
JBCA Colloquium
Dr. Chris Harrison
(ESO) |
Resolving the impact of AGN on the evolution of massive galaxies |
| Abstract: It is almost universally accepted that accreting supermassive black holes play a crucial role in the evolution of massive galaxies. However, this is largely based on the failure of cosmological simulations to produce realistic looking galaxy populations without significant energy input from such active galactic nuclei (AGN). Consequently, many questions remain unanswered on how this process actually operates in the real Universe. In this talk I will outline our multi-facetted approach to provide the observations required to understand this process. We have been observing large samples of galaxies covering 10 Gyrs of cosmic time to obtain spatially-resolved measurements of the gas kinematics to search for, and to characterize, ionised outflows. By combining these measurements with high resolution radio imaging from eMERLIN and VLA we are establishing the role and impact of radio jets, even in systems that have low radio luminosities. We have also used our ALMA observations to obtain high quality star formation rate constraints (both resolved and unresolved) to determine what impact AGN can have on the star formation inside their host galaxies. By combining our systematic observational campaigns with cutting-edge simulations, we are building up a complete picture of the impact of AGN on the evolution of massive galaxies.
Host: Alasdair Thomson |
| Nov 1 |
Special Seminar
Dr. George Heald
(CSIRO Astronomy & Space Science) |
The nexus of Australian marsupials and broadband radio polarimetry |
| Abstract: With the advent of broadband frequency coverage on modern radio interferometers, we are entering a new age of radio polarimetry. Exquisite broadband polarimetry provides a unique view on the detailed magnetic and ionised structure within radio-emitting objects such as star-forming galaxies and AGN. We also have unique access to the time variability of magnetic structures within sources, in a manner complementary to VLBI observations. In this presentation I will describe new, ongoing survey efforts in this direction across a wide range of frequency using Australian radio telescopes: the Murchison Widefield Array (MWA), the Australian SKA Pathfinder (ASKAP), and the Australia Telescope Compact Array (ATCA). This overview will include new data and new results, and will star a few marsupials. I will also place this fresh observational progress in the context of the extraordinary magnetism science that is now being enabled by LOFAR. The talk will conclude with some thoughts on the future of this field as we move toward the era of the SKA itself.
Host: Paddy Leahy |
| Nov 7 |
JBCA Colloquium
Dr. Joe Callingham
(ASTRON) |
Absorption processes in radio astronomy: Facilitating a unique discovery space |
| Abstract: One of the most common assumptions in radio astronomy is that the continuum spectrum of a radio source follows a simple power-law. Such an assumption is being challenged by the data being produced by the new sophisticated megahertz-sensitive telescopes and broadband gigahertz-receivers, as we can now sample the spectra of radio sources at a level of detail never before achievable. We are finding that a power-law description is inappropriate for many radio sources, particularly at low frequencies where absorption processes become significant. I will outline in my talk how low-frequency absorption processes provides us with a unique tool to test radio galaxy evolutionary models, mass loss scenarios of progenitor stars to supernovae, and a way to identify exoplanets. In particular, I will demonstrate that probing these absorption processes opens up an untapped discovery space for exotic objects that have been missed in more traditional spectral searches.
Hosts: Alex Clarke, Rachael Ainsworth |
| Nov 14 |
Schuster Colloquium
Dr. Kate Shaw
(Sussex University) |
Promoting Physics Worldwide |
| Abstract: There is a significant untapped potential of physicists that come from developing countries. Strong young students may lack exposure to physics and physics research, they may not be aware of opportunities for further study, and governments and institutions may not fully recognise the importance of investing into the fundamental sciences. Promoting physics worldwide, and in particular in developing countries, can play a key role in promoting the growth and development of scientific culture. Our scientific community must support education and the development of research worldwide. This talk will discuss the respective issues encountered by countries in the development of physics research are presented along with how our community can support their endeavour with some focus on the ICTPs Physics Without Frontiers program.
Host: Marco Gersabeck |
| Nov 21 |
JBCA Colloquium
Dr. Thomas Collett
(ICG Portsmouth) |
Testing the LCDM paradigm with strong gravitational lenses |
| Abstract: Local measurements of the expansion rate are in tension with those inferred from observations of the distant Universe. Is this the first sign of new physics or merely a sign of systematic errors within individual probes? This key question remains unsolved, because there are only a handful of established probes. Here I will talk about how strong gravitational lensing offers a new window on precision cosmology, shining a new light on the dark Universe. I will present strong lensing constraints on the expansion rate of the Universe and the equation of state of dark energy. I will also show how lensing combined with stellar dynamics yields the most precise test to date of the validity of General Relativity on extragalactic scales.
Host: Neal Jackson |
| Nov 22 |
Special Seminar
Dr. Atsuhisa Ota
(Cambridge University) |
CMB spectral distortions in the framework of cosmological perturbation theory |
| Abstract: The cosmic microwave background (CMB) spectral distortions, the deviations from the CMB blackbody spectrum contain various information of the early universe. In particular, it is complementary to what we obtained from the standard linear anisotropy of the CMB, and hence the importance of theoretical and observational understandings of the spectral distortions is increasing. In this presentation, I will talk about the spectral distortions originated from primordial density fluctuations generated during cosmic inflation.
I will give a brief introduction to nonlinear cosmological perturbation theory in the presence of spectral distortions. Then, I will discuss how to extract the primordial physics such as non-Gaussianity of primordial density perturbations and the statistical anisotropy from the spectral distortions within the framework.
Hosts: Andrea Ravenni and Jens Chluba |
| Nov 28 |
JBCA Colloquium
Dr. Anastasia Fialkov
(Harvard/Sussex) |
Evaluating Cosmic Dawn |
| Abstract: Cosmic dawn is one of the least-explored epochs in the history of the Universe illuminated by the very first stars and black holes. 21-cm radio signal produced by the intergalactic neutral hydrogen is tied to the intensity of radiation generated by the first sources of light. The signal can be used to constrain process of primordial star and black hole formation as well as reionization. In my talk I will discuss first observational constraints on this epoch established by global 21-cm experiments at redshifts z~6-14. Pioneering radio experiments such as EDGES High-Band and SARASII deliver data which are capable to disfavor large sections of the high-redshift astrophysical parameter space. I will also discuss combined constraints with high-redshift quasars and Lyman Break Galaxies. Finally, I will comment on the claimed detection made with the EDGES Low-Band antenna at z~17.
Hosts: Keith Grainge and Jens Chluba |
| Nov 29 |
Special Seminar
Dr. Yan-Chuan Cai
(Institute for Astronomy, University of Edinburgh) |
Cosmology with the cosmic web |
| Abstract: On large scales, the matter distribution of the Universe follows a web-like pattern, consisting of knot (cluster), filament, sheet and void. The cosmic-web is a non-Gaussian field, containing invaluable information about cosmology and astrophysics. I will summarise recent research activities in trying to extract this information. I will highlight opportunities and challenges for clusters and voids, and show evidence for filaments between pairs of galaxies.
Host: Jens Chluba |
| Dec 5 |
Schuster Colloquium
Prof. Mark Lancaster
(UoM) |
Is new physics lurking in the magnetic interaction of a muon? |
| Abstract: The interaction of a muon's spin with a magnetic field defines its
magnetic moment in terms of the gyromagnetic ratio, g. In the Dirac
equation, g is exactly 2, but additional higher order QED, electroweak and strong interactions increase its value by ~ 0.1% such that g-2 is predicted to be: 0.0023318364(7). g of the electron is the most accurately predicted and measured quantity in physics and g of the muon is the most accurately measured quantity using a particle accelerator storage ring.
At present there exists a discrepancy between the measurement of the
muon's g-2 (0.0023318418(13)) and the prediction with a significance of
3.6 standard deviations. Whether this is telling us that there is new physics beyond the Standard Model of particle physics e.g. that could explain the matter antimatter asymmetry of the universe or a statistical fluctuation will be resolved by a new experiment that has recently started taking data at Fermilab, USA. I will describe the history of this measurement and the new experiment and how we expect to achieve a precision of 0.14 parts per million on this exciting new measurement and so hopefully resolve whether the magnetic interaction of a muon is a harbinger of new physics.
Host: Stefan Soldner-Rembold |
| Dec 12 |
JBCA Colloquium
Prof. Ian Browne
(UoM) |
New evidence for large-scale AGN axes alignments in the Universe |
| Abstract: I will talk about some work in progress! Starting with a somewhat controversial claim about the large-scale alignment of AGN polarization position angles, and adding the ingredient of unified models of radio sources, leads to a bold prediction that flat spectrum radio sources should display an apparent clustering signal much stronger than steep spectrum sources. We have tested this prediction using samples of radio sources selected from large area radio surveys. To our surprise, as predicted, we detect a much stronger clustering in the flat spectrum population than in the steep spectrum population. The difference persists on scales of ~20 degrees. I will discuss whether this difference is real or caused by some subtle selection effect. If real, the result implies that the angular momentum axes of AGN are strongly aligned in volumes of space up to ~Gpc in size. It will open a new window for large scale structure formation studies.
Host: Rachael Ainsworth |
| Dec 19 |
JBCA Colloquium
Dr. Simon Purser
(Dublin Institute for Advanced Studies) |
Surveys of Radio Jets from Young Stellar Objects |
| Abstract: Accretion and ejection are intimately linked through disc-based paradigms of star formation. Through optical, near-infrared and radio observing programmes, high-velocity, collimated, and partially-ionised jets have been ubiquitously associated with low-mass (< 8 solar masses) young stellar objects (YSOs). However, the question as to whether this ubiquity extends to massive star formation remains unanswered due to high extinction, source confusion and large distances. In this talk, I shall inform the audience on a VLA/ATCA, all-sky, radio survey of massive YSOs sampled from the Red MSX Source (RMS) survey. Not only will I show that collimated ejection phenomena are common towards MYSOs but, unexpectedly, that they are also often associated with non-thermal emission from a shock-accelerated population of relativistic electrons. Further to this, many of their properties scale with the bolometric luminosity of the YSO in much the same way as with their low-mass brethren, supporting the case for a common star formation process. To conclude I will discuss future work, including an e-MERLIN survey for which our Northern Hemisphere, VLA observations were designed as a matching-beam precursor. In combination with the (low-mass) Ejection Accretion Structures around YSOs (EASY) project (again, e-MERLIN) we will have a complete census of ionised jets across the entire mass regime. Importantly the high resolution capabilities of the (soon to be) upgraded e-MERLIN should allow us to discern between competing ejection/collimation mechanisms of the jets themselves.
Host: Rachael Ainsworth |
| Jan 16 |
JBCA Colloquium
Prof. Stephane Corbel
(Nancay) |
The Nancay Radio Observatory |
| Abstract: Nancay is a remote village located in the middle of a forest in the Sologne area, a remote place
located 80 km South of Orléans (or 250 km from Paris). Following the huge development of radio
astronomy after the 2nd World War, Nancay hosted the French effort towards radio astronomy with
the creation of the Observatory in 1953. Today, the Nancay Radio Astronomy Facility is jointly
operated by the Paris Observatory, the CNRS, and the University of Orleans.
The site is quite large (150 hectares) and beside the historical instruments (the Big Radiotelescope,
the radioheliograph and the decameter array), it is also now part of the LOFAR array with one
station located in the Observatory. We are also building the NenuFAR array, which will be extremely
sensitive at low radio frequencies. In addition, the Observation has also been involved in some of the
most recent advances in R&D for future radio observatories and instrumentation.
In this Colloquium, I will present a very general overview of the Observatory focusing on some of the key
elements today.
Hosts: Rene Breton & Ben Stappers |
| Jan 23 |
JBCA Colloquium
Dr. Olivia Jones
(UK ATC) |
The life-cycle of dust in galaxies: IR Stellar populations in the JWST era |
| Abstract: The James Webb Space Telescope (JWST) is a large aperture, cryogenic, infrared space observatory due to launch in 2021. It will provide imaging, spectroscopic and coronagraphic capabilities from 0.6 to 28.5 microns with an unprecedented combination of sensitivity and spatial resolution. The breakthrough capabilities of JWST and its and suite of scientific instruments will enable new studies of star formation and stellar evolution in the Milky Way, nearby galaxies, and the early universe. This presentation will provide an overview of JWST, along with a description of some of the scientific goals and objectives. Highlighting observations of IR stellar populations, star formation and stellar death that will be conducted by JWST as part of our GTO program, both locally and at low metallicity.
Host: Iain McDonald |
| Jan 30 |
JBCA Colloquium
Prof. Peter Gallagher
(DIAS) |
The Shocking Radio Sun (CANCELLED) |
| Abstract: Coronal mass ejections (CMEs) are large-scale eruptions of plasma and magnetic field from the Sun. As they expand into interplanetary space, they can produce radio bursts at decametric and metric radio frequencies (~10-500 MHz), which are thought to be associated with shocks. In this talk, I will describe how CME kinematics derived from SOHO and STEREO coronagraphs can be combined with dynamic spectra and radio images from instruments such as e-Callisto, LOFAR and the Nancay Radioheliograph to give us a better understanding of shock formation. I will also describe how SDO/AIA and SOHO/LASCO images can be combined with potential field extrapolations to construct Alfven speed maps of the corona in order to study how and where shocks are formed.
Bio: www.dias.ie/petertgallagher
Host: Philippa Browning |
| Feb 6 |
JBCA Colloquium
Dr. Fabio Antonini
(University of Surrey) |
Nuclear clusters and (supermassive) black holes |
| Abstract: Massive stellar clusters are often found at the photometric and kinematic centres of galaxies. Such nuclear clusters are the densest stellar systems observed in the local universe, and represent an environment where compact object binaries can frequently form, harden and merge. I will discuss the dynamical processes that lead to the merger of black hole binaries in nuclear clusters in connection to the origin of the binary black hole mergers recently detected by Advanced LIGO. I will show that nuclear clusters can produce a significant population of black hole binaries that merge in the local universe, and that these binaries have clear differences in the statistical distributions of their properties (e.g., mass, eccentricity) when compared to those formed either in globular clusters or through isolated binary evolution. Finally, I will consider the evolution of supermassive black hole binaries that are formed in nuclear clusters during the merger of galaxies. The results of N-body and Monte Carlo simulations show that coalescence times fall in the range from 10^8 yr to a few Gyr. These results constitute a fully stellar-dynamical solution to the ''final-parsec problem'' and imply a high rate of events for planned low-frequency gravitational wave detectors like LISA.
Host: Jens Chluba |
| Feb 13 |
JBCA Colloquium
Dr. Pranjal Trivedi
(University of Hamburg) |
Cosmic Probes of Primordial Magnetic Fields and Axion-like Dark Matter |
| Abstract: The Universe is magnetized on large scales yet the origin of cosmic magnetic fields is unresolved and magnetogenesis could have occurred in the early Universe. I will discuss the evolution of such primordial magnetic fields across the cosmological recombination epoch via 3D magnetohydrodynamic simulations. We compute the net heating rate of baryons due to decaying magnetic fields and find three distinct regimes: drag-dominated, transition and turbulent decay. Both the peak of the net heating rate and the onset of turbulent decay are delayed significantly beyond recombination for scale-invariant magnetic fields. These results can be used to place cosmic microwave background (CMB) constraints on primordial magnetic fields.
Magnetic fields have also been important in searches for axion-like particles, a leading dark matter candidate, using axion-photon conversion. However, searches for axion signals remain fraught with uncertainties regarding the distribution of cosmic magnetic fields. I will present a sensitive cosmological probe for axion-like dark matter that is independent of magnetic fields — birefringence in the CMB. Birefringence arises from the oscillating axion-like particle's effective refractive index. CMB observations imply that birefringence improves constraints on the axion-photon coupling by three to four orders of magnitude for ultra-light axion-like particles. Ongoing and proposed laboratory searches for axions also employ birefringence.
Host: Abir Sarkar and Jens Chluba |
| Feb 27 |
JBCA Colloquium
Dr. Emily Petroff
(University of Amsterdam) |
Fast Radio Bursts: New discoveries and future prospects |
| Abstract: Fast radio bursts (FRBs), bright millisecond duration radio transients, are quickly becoming a subject of intense interest in time-domain astronomy. FRBs have the exciting potential to be used as cosmological probes of both matter and fundamental parameters, but such studies require large populations. Advances in FRB detection using current and next-generation radio telescopes will enable the growth of the population in the next few years from 30 to hundreds. Real-time discovery and follow-up, and new studies of the FRB population will provide us with some of the greatest insights in the coming years. I will discuss many observational aspects of the FRB population, including polarisation, searches for multi-wavelength emission, localisation, and repeating FRBs. I will also discuss how our response to these events can inform next generation surveys and pave the way for the enormous number of FRB discoveries expected in the SKA era.
Host: Ben, Rachael |
| Mar 6 |
Bragg Lecture
Prof. Rashid Sunyaev
(Max-Planck Institute for Astrophysics, Garching) |
X-Ray and Microwave Cosmology: synergy and competition -- What can we expect from SRG/eRosita and new ground-based microwave telescopes? |
| Abstract: Our Universe is filled by cosmic microwave background radiation (CMB) which is extremely isotropic and has an excellent blackbody spectrum at temperature 2.726 Kelvin, with no departures from the blackbody spectrum detected so far. However, 50 years ago, my Mentor Yakov Zeldovich and I predicted the presence of "shadows" in the angular distribution of the CMB in directions where clouds of very hot electrons (Te~10^6-10^8 K) are present. Today we know that such objects exist as clusters of galaxies containing thousands of galaxies each, a lot of dark matter, and a hot gas filling their huge potential wells. The "shadows" with very peculiar frequency spectrum and signal amplitude corresponding to a few tens or hundreds of microKelvin arise due to Thomson interactions of CMB photons with hot electrons. Today this effect permitted us to discover several thousands of previously unknown clusters of galaxies at relatively high redshifts 0.25 < z < 2. Behind practically every newly discovered rich cluster of galaxies we see the extremely distant galaxies with shape distorted and brightness increased due to gravitational lensing by huge gravitational potential of a cluster connected mainly with the invisible "dark matter".
There is also a more common way to observe the same hot gas using X-rays. This June, Russia plans to launch the SRG spacecraft with German eRosita X-Ray telescope supplied with grazing incidence optics. This telescope will discover more than 100,000 clusters of galaxies (i.e. all rich clusters of galaxies in the observable Universe) during 4 years of its all-sky survey. At the same time, ground-based millimeter wavelengths telescopes at the South Pole and Atacama desert at 5 km altitude, equipped with tens of thousands of cryogenic bolometers in their focal planes, promise to detect all these clusters due to their "shadows" in the CMB.
The datasets will be highly complimentary because the X-ray emission due to free-free emission of the hot gas is proportional to the square of the electron density and amplitude of shadows depends linearly on the plasma pressure Pe~NeTe. There will thus be a lot of synergy. At the same time there is competition: who will be first to discover the most interesting clusters of galaxies? Ensembles of 10^5 clusters, their distribution in space, mass and redshift will provide a unique data sample for testing cosmological models.
Interactions of CMB photons with free electrons also open a unique way to measure the peculiar velocity of clusters relative to the unique system of coordinates in which CMB is isotropic. Observers can now measure peculiar velocities and even bulk and turbulent velocities inside clusters of galaxies at any distance from us because both effects (thermal and kinematic) do not depend on the redshift of the object. This will open additional exciting scientific opportunities which I will briefly touch on in my lecture.
Host: Richard Battye and Jens Chluba |
| Mar 7 |
Special Seminar
Dr. Syksy Rasanen
(University of Helsinki) |
The gravity track of Higgs inflation |
| Abstract: Using the Standard Model Higgs as the inflation is attractively
economical. Higgs inflation is simple at the core, but there are
complications both on the side of quantum corrections and gravity. I will
discuss possibilities and problems due to such complications. In
particular, I will address generating black holes to be dark matter, and
determining the gravitational degrees of freedom.
Hosts: Boris Bolliet and Fedor Bezrukov |
| Mar 13 |
JBCA Colloquium
Dr. Jack Radcliffe
(Pretoria, Groningen & JBCA) |
Finding AGN in the faint radio sky |
| Abstract: It is now widely accepted that the evolution of galaxies and the growth of the central supermassive black hole (SMBH) are intimately connected. Those SMBH which are active (hence Active Galactic Nuclei/AGN) have been shown to influence the host galaxy and such feedback mechanisms are also required by simulations. This makes understanding the abundances and influence of AGN in distant galaxies one of the hottest research topics around. While other multi-wavelength studies are invariantly affected by dust; radio, fuelled by the burgeoning capabilities of modern arrays, can provide a dust-free window into star-formation and AGN activity. However, many radio surveys are often have resolutions in excess of arcsecond which are insufficient to separate AGN and star-formation activity. To infer the existence of an AGN relies multi-wavelength diagnostics (e.g. X-rays, infra-red, radio-excess) which are often unreliable and incomplete.
There is one key weapon missing from the AGN identification arsenal namely high resolution radio observations. Here, we can isolate high brightness temperature objects (>1E5 K) which can only be attributed to AGN in distant galaxies. In this talk, I will dispel the myth that high resolution radio surveys are constrained to small fields of view, and I'll outline the developments that have made surveying degrees of the sky at milliarcsecond resolutions easy and routine (VLBI astronomers are not the black-belt radio astronomers anymore!). Using the GOODS-N field as an example, I will briefly outline the pros and cons of AGN selection via high resolution radio observations followed by some initial results from the upcoming first data release from the e-MERLIN Galaxy Evolution (e-MERGE) survey.
Host: Rob Beswick |
| Mar 27 |
JBCA Colloquium
Dr. Silvia Galli
(IAP) |
Cosmological results from the final data release of the Planck satellite |
| Abstract: Planck is an ESA satellite aimed at the observation of the Cosmic Microwave Background. In the last few months, the Planck collaboration has released its final data and results. In this talk, I will describe the main results on cosmology from the mission, highlighting the changes with respect to previous releases, the agreement with other cosmological probes and the unsolved questions opened for the future.
Host: Jens Chluba and Luke Hart |
| Apr 3 |
Schuster Colloquium
Prof. Lucie Green
(MSSL) |
Origins and impact of space weather |
| Abstract: Space weather is the phrase used to describe changes in the near-Earth space environment that are caused predominantly by solar activity. These forms of solar activity include solar flares and coronal mass ejections. During times of stormy space weather, there can be a knock-on effect on many of the technologies that modern society relies on and this had led to the Met Office being tasked with providing daily space weather forecasts. This talk will show the dynamic side of the Sun and discuss the origins of space weather and what we are doing today to protect ourselves.
Host: Philippa Browning |
| Apr 24 |
JBCA Colloquium
Willice Obonyo
(University of Leeds) |
A search for non-thermal radio emission from jets of massive protostars |
| Abstract: Massive young stellar objects (MYSOs) have recently been shown to drive jets whose particles can interact with either the magnetic fields of the jet or ambient medium to emit non-thermal radiation. We report a search for non-thermal radio emission from a sample of 15 MYSOs to establish the prevalence of the emission in the objects. We used their spectrum across the L-, C- and Q-bands along with spectral index maps to characterise their emission. We find that about 50% of the sources show evidence for non-thermal emission with 40% showing clear non-thermal lobes, especially sources of higher bolometric luminosity. All the central cores of the sources are thermal with corresponding mass-loss rates that lie in the range 3x10^-7 to 7x10^-6 solar masses per year. Given the presence of non-thermal lobes in some of the sources and the
evidence of non-thermal emission from some spectral index maps, it seems that magnetic fields play a significant role in the jets of massive protostars. Also noted is that some of the sources show evidence of binarity and variability.
Host: Anna Scaife |
| May 1 |
JBCA Colloquium
Dr. Leah Morabito
(Oxford) |
Active galactic nuclei: a low frequency perspective |
| Abstract: Almost every massive galaxy is believed to have a super-massive black hole in its centre, and there is clear evidence this can influence a galaxy’s evolutionary path. These super-massive black holes are a small fraction of a galaxy’s overall mass, yet there are tight correlations between the mass of the black hole and general properties (e.g., mass) of the galaxy. The physical processes which govern the co-evolution of the super-massive black holes and their host galaxies are still unknown, but advances in low frequency radio astronomy can offer new insights. I will present several ways which low frequency observations can help advance our understanding of this co-evolution, which will include studies of individual objects as well as surveys, and give an outlook for the future of low-frequency radio astronomy. In particular I will focus on wide area surveying at sub-arcsecond resolution, made possible with the unique capabilities of the LOw Frequency ARray (LOFAR).
Host: Neal Jackson |
| May 8 |
Schuster Colloquium
Prof. Timothy Spiller
(University of York) |
Quantum Technologies |
| Abstract: Quantum technologies are new disruptive technologies in which fundamental aspects of quantum physics are instrumental in providing advantages over the conventional technology counterparts. Examples include quantum computing, sensing, imaging and communications; I'll outline examples and illustrate their "quantum advantage", before discussing quantum communications in more detail. I'll give a very brief overview of what is being pursued in the UK National Quantum Technologies Programme, and then expand on the technologies being delivered by the Quantum Communications Hub.
Host: Ahsan Nazir and Jens Chluba |
| May 15 |
JBCA Colloquium
Dr. Colin Hill
(IAS Princeton / Flatiron Institute) |
Cosmic Microwave Backlight: Illuminating Large-Scale Structure with the Universe’s Oldest Photons |
| Abstract: Observations of the cosmic microwave background (CMB) radiation have driven the current era of precision cosmology. Nevertheless, substantial information remains to be extracted from the primary CMB polarization anisotropies -- including the signature of primordial gravitational waves -- as well as the "secondary anisotropies" generated by effects between our vantage point and the surface of last scattering. The latter signals, including gravitational lensing and the thermal and kinematic Sunyaev-Zel’dovich (SZ) effects, also contain valuable astrophysical information about the distribution of baryons and dark matter. I will present recent and ongoing work to extract these signals in data from the Atacama Cosmology Telescope (ACT) and the Planck satellite, as well as next-generation forecasts for the Simons Observatory (SO), which will begin observations in the early 2020s. I will show that current thermal and kinematic SZ measurements are already providing insight into feedback processes in structure formation, and that upcoming data will clearly distinguish between predictions from state-of-the-art cosmological hydrodynamics simulations of galaxy formation. I will conclude with a discussion of ongoing work to constrain the sum of the neutrino masses via high-precision CMB lensing and SZ measurements, focusing on recent progress in overcoming foreground-related challenges in this program, in anticipation of a detection with ACT/SO within the next decade.
Host: Boris Bolliet and Jens Chluba |
| May 16 |
Special Seminar
Dr. Clancy James
(Curtin University) |
Through a glass darkly: what do we really know about fast radio bursts? |
| Abstract: Fast radio bursts (FRBs) are powerful extragalactic bursts of radio waves with millisecond duration. Their origin is a mystery, with dozens of theories, from supramassive neutron stars to lensing by astrophysical plasmas, being proposed to explain their extreme energies. An ultimate goal is to use FRBs to probe the intergalactic medium and search for the missing baryonic mass of the universe. However, even basic questions surrounding FRBs, such as "do they all repeat?", "do they originate in the near or distant universe?", and "what is their intrinsic luminosity function?" remain unanswered.
Attempts to resolve these questions have been both helped and hampered by the plethora of experiments used to study them. The effects of various detection parameters - telescope beamshape, search algorithms etc - interact with a poorly understood luminosity function to obscure intrinsic FRB properties. In this talk, I present the latest results from, and analysis of, FRB data from The Commensal Real-time ASKAP Fast Transients Survey (CRAFT). I then comment on what progress we, and others, have made towards answering these questions.
Host: Justin Bray |
| May 22 |
JBCA Colloquium
Dr. Juan Hernandez
(Anton Pannekoek, University of Amsterdam) |
A multi-wavelength view of the puzzling behaviour of transitional millisecond pulsars |
| Abstract: Transitional millisecond pulsars are a new class of binary neutron star-main sequence star systems recently discovered in the last decade. These systems are observed to cycle between states of detached radio millisecond pulsar and interacting disc-dominated X-ray pulsar in time-scales of a decade. They provide direct evidence for the recycling of old-slow spinning neutron stars into the millisecond regime. Therefore, they represent an ideal laboratory to understand the evolution and present-day population of old - yet- rapidly spinning neutron stars. In this talk I will review our current understanding of these new elusive class of systems. I will present some recent results from our multi-wavelength campaign to unravel the different inflow/outflow properties during the disc state and provide some insights on their complex observational features.
Host: Alex Clarke |
| Jun 5 |
JBCA Colloquium
Dr. Sadie Jones
(University of Southampton) |
Engaging publics with Supernova and Dark Energy research at the University of Southampton |
| Abstract: The talk details four separate public engagement activities that have showcased the Supernova research of the University of Southampton Astronomy group. Firstly #AstroAirport took place in the Southampton Airport departure lounge for 4 days in 2016; at this event we aimed to engage young families with Supernova research during the half term break. Then, the SETI Cipher Challenge is an online forum event that engages school children and teachers across the UK for a week at the end of the summer term, the challenge took place 4 times between July 2013 – July 2016. Finally the #SotonAstroArt exhibit, art workshops and Dark Energy film project, which is ongoing, links directly to our Dark Energy Survey (DES) research with a focus on local artists, public attending humanities festivals, youth groups, home educator groups and libraries attendees. Sadie will present evaluation data from these four projects and discuss their challenges and successes.
Host: Alex Clarke, Tana Joseph, Rachael Ainsworth |
| Jun 12 |
JBCA Colloquium
Dr. Mark Neyrinck
(University of the Basque Country, Bilbao) |
Spinning (in) a Cosmic Spiderweb |
| Abstract: Artists and scientists have noted the visual similarity between the cosmic web and other networks in nature. I will mention a rigorous physical correspondence between the cosmic web, in a formalism called the adhesion model, and architectural structures known as spiderwebs (networks of strands that can exist entirely in tension), and also to origami. Investigations of the adhesion model led to new work on how galaxies acquire angular momentum, through angular-momentum "conservation" (in a particular comoving sense) within evolving primordial patches. The standard tidal-torque theory of galaxy spin-up is an approximation to this picture, and many of its predictions are similar. But the proposed picture is more accurate and (arguably) more conceptually intuitive.
Host: Jens Chluba |
| Jun 17 |
Special Seminar
Dr. Santiago Pinzon
(Univ. nacional de Colombia) |
Latinoamerican VLBI Network InitiativeHydrogenbursts? |
| Abstract: TBD
Host: Sally Cooper, Anna Scaife |
| Jun 24 |
Special Seminar
Dr. Eloy de Lera Acedo
(Cavendish Laboratory) |
REACH: Radio Experiment for the Analysis of Cosmic Hydrogenbursts? |
| Abstract: The first stars and galaxies formed some time after the epoch of cosmic recombination (when the Cosmic Microwave Background formed ~378,000 years after the Big Bang at a redshift (z) of ~1100) and before the current 'realm of the galaxies' that we can see today (~1 to 13.7 billion years after the Big Bang). The radiation from these first luminous sources heated and re-ionized the neutral hydrogen that pervaded the primordial Cosmos. Probing these epochs, the 'Dark Ages' before the first galaxies, through cosmic re-ionization and first new light in the Universe, represents the frontier in studies of cosmic structure formation. Neutral hydrogen has a rest wavelength of 21 cm and by observing at low radio frequencies we can study directly its red-shifted radio emission (and absorption) from the gas clouds that were the raw material that formed the first luminous cosmic structures at these early epochs. While the SKA telescope will aim to do full tomography of the hydrogen emission from the Cosmic Dawn and the Epoch of Re-ionization, an in principle simpler way to attempt the detection and study of this signal aims to observe the monopole emission (averaged from all directions in the sky) through cosmological time, red-shifted from 21-cm to a few meters due to the expansion of the Universe, with a stand alone radiometer system. In this talk I will present REACH, a new experiment led by Cambridge (Cavendish Astrophysics, KICC) to attempt the detection and subsequent analysis of the redshifted 21 cm line from the Cosmic Dawn and the Epoch of Re-ionization.
Host: Keith Grainge |
| Jun 27 |
Special Seminar
Dr. David Tabb
(University of Stellenbosch) |
Biomarkers for Better Birthdays |
| Abstract: One of the least pleasant aspects of aging is the increased risk of disease. Each of us faces a rather stark battery of tests as we reach 50
years of age, and none elicits more grimaces than does the dreaded colonoscopy.
In this talk, Dr. Tabb describes a ten-year effort at Vanderbilt University for colon cancer biomarkers that “failed forward”, producing many tantalizing
leads but not producing the clinical test it sought. Just what are biomarkers? Why are they believed to be the road forward for personalized medicine?
Host: Sally Cooper and Rene Breton |
