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 |
|---|
| Aug 19 |
Special Seminar
Dr. Dayang Nurfatimah,
(UNIMAS, Malaysia) |
EXPANDING THE POWER OF DEEP LEARNING FOR ASTRONOMY |
| Abstract: AI technology enables systems to learn, machine learning is pushing the innovation boundaries in various domains from healthcare to financial services. Machine learning and image analysis for astronomy has been explored more than a decade ago. Big data is transforming how astronomers make discoveries, where data volumes of entire surveys can now be acquired in a single night and real-time analysis is often desired. In this presentation, I will cover the use of AI in astronomy and direction for our joint research project - Deep Learning for Classification of Astronomical Archives.
Host: Albert Zijlstra |
| Aug 21 |
Special Seminar
Dr. Peter Taylor,
(MSSL) |
Next Generation Cosmological Inference from Weak Lensing Surveys |
| Abstract: Next generation surveys including Euclid, LSST and WFIRST will increase the statistical power of weak lensing experiments by more than an order of magnitude — yet the way we perform cosmological inference has not fundamentally changed for over a decade. In this talk I present three new methods for extracting cosmological information which all address shortcoming with the standard approach. The first of these, called k-cut cosmic shear, allows us to remove sensitivity to poorly understood small-scale baryonic physics. Next I discuss how to extract information about the growth of structure and background expansion directly — with no a priori assumption about the underlying cosmological model. Finally I show how to perform Bayesian ‘likelihood-free’ cosmological parameter inference using only a small number of forward model realisations of the data.
Host: Lee Whittaker |
| Sep 18 |
Special Seminar
Prof. Yin-Zhe Ma
(University of KwaZulu-Natal) |
Detection of the warm-hot baryons in the Universe |
| Abstract: Previous studies of galaxy formation have shown that only 10 per cent of the cosmic baryons are in stars and galaxies, while 90 per cent of them are missing. In this talk, I will present three observational studies that coherently find significant evidences of the missing baryons. The first is the cross-correlation between the kinetic Sunyaev-Zeldovich maps from Planck with the linear reconstructed velocity field. We find significance (4.6 sigma) detection of the peculiar motion of gas on Mpc scales, for which we can reconstruct the baryon fraction. The second study is the cross-correlation between the thermal Sunyaev- Zeldovich effect with gravitational lensing map and we detect the cross-correlation for 13 sigma with RCSLenS and Planck data. The third study is to stack the pairs of luminous red galaxies and subtract the halo contribution, which leads to the detection of gas within filaments. The last study is the dispersion measurement of the kSZ effect from MCXC cluster, which is measured at 2.8 sigma C.L. I will discuss the implication of these results.
Host: Richard Battye and Jens Chluba |
| Sep 25 |
JBCA Colloquium
Dr. Simon Johnston
(CSIRO, Australia) |
The evolution of pulsars on short and long timescales |
| Abstract: The pulsar astronomer's equivalent of the Hertzsprung-Russell diagram is the P-Pdot plane. Populating this plane with the 2600 known pulsars allows us to develop ideas about how fast pulsars spin at birth, how they evolve with time and how millisecond pulsars and magnetars originate. I will discuss the long-term evolution of pulsars and also focus on what we've learned in the few decades since pulsars were discovered about evolution on short timescales. Together, these give insight into the conditions in the magnetosphere and interiors of pulsars and have implications for the continuing quest to detect gravitational waves from the stochastic black-hole background.
Host: Patrick Weltevrede |
| Oct 2 |
JBCA Colloquium
Dr. Blake Sherwin
(University of Cambridge) |
Fundamental Physics from CMB Lensing: New Data and New Approaches |
| Abstract: The dark matter distribution in the universe contains a wealth of information about neutrinos, dark energy, and the physics of the very early universe. Measurements of gravitational lensing in the cosmic microwave background (CMB) allow this matter distribution to be directly seen and mapped out to uniquely high redshifts. In my talk, I will first describe current and future lensing measurements and cosmological constraints from the ACT, Simons Observatory and CMB-S4 CMB experiments. I will then discuss the development of a new, improved method for small-scale lensing reconstruction. Lensing is not only a signal, however, but also a source of noise that limits how much we can learn about inflation and the early universe. With illustrations from recent work, I will explain how de-lensing - removing the lensing effect to reveal the primordial polarization sky - will be crucial for the future of CMB cosmology.
Host: Jens Chluba and Richard Battye |
| Oct 9 |
Schuster Colloquium
Dr. Adam Aitkenhead
(Christie NHS Foundation Trust) |
Proton therapy at the Christie |
| Abstract: In December 2018 the Christie NHS Foundation Trust opened a new proton beam therapy (PBT) facility. This is the first NHS high-energy PBT centre in the UK as part of a £250M NHS England funded programme to provide a national PBT service, with a second centre due to open at University College London Hospitals NHS Foundation Trust in 2020. The NHS high-energy PBT service in the UK was 10 years in development, and when running at full capacity is expected to provide treatment to up to 1500 patients per year across the two centres.
This lecture will cover the rationale behind the use of high-energy (up to 245 MeV) protons for radiotherapy, highlighting the differences between PBT and current state-of-the-art gamma ray radiotherapy which arise due to the underlying physics. It will present an overview of the technologies used to deliver the proton beam to the patient, and the methods of treatment planning that clinical physicists use to ensure that the prescribed dose is delivered to the target (i.e. the tumour) while minimising the dose delivered to surrounding normal tissues. Current and future areas of research and development in the areas of delivery, planning, imaging and radio-biological modelling will also be presented.
Hosts: Jens Chluba |
| Oct 16 |
JBCA Colloquium
Dr. Laura Wolz
(JBCA Manchester) |
Galaxy Evolution with HI Intensity Mapping |
| Abstract: Intensity mapping surveys of neutral hydrogen (HI) are a novel way to measure the large scale matter distribution of our Universe and thus constrain cosmological parameters describing the Universal expansion. The next generation of radio telescopes and interferometers are being designed and built to optimise the detection of the HI line at low spatial resolution allowing efficient mapping of large volumes. The impact of instrumental systematics of radio observations on cosmological measurements can be significantly reduced by cross-correlating the HI signal with galaxy surveys. The cross-correlation also offers an innovative way to statistically detect the average HI content of the optically-selected galaxy sample since the noise on the cross-power spectrum measurement scales with the galaxy HI temperature. I will give an introduction into the intensity mapping technique and prospects of the on-going and future experiments, such as the Square Kilometre Array (SKA). I will review the latest HI signal detection in data such as the Parkes telescope in cross-correlation with the 2dF galaxy survey or the Green Bank Telescope intensity maps. I will present studies on the potential of future intensity mapping experiments in constraining galaxy evolution processes, such as the global HI density as well as HI scaling relations in galaxies. I will show how the SKA and its pathfinder experiments can detect the relevant scales of the cross-power spectrum and probe the HI content of medium redshift galaxies to faint for direct detection with radio telescopes.
Host: Richard Battye and Jens Chluba |
| Oct 23 |
JBCA Colloquium
Dr. Wendy L. Williams
(Sterrewacht Leiden) |
The radio AGN population revealed by LOFAR |
| Abstract: I will present some radio AGN science results from LOFAR, including the first data release of the LOFAR Two-metre Sky Survey (LoTSS). I will discuss some of the details behind calibration and imaging at low radio frequencies as well as the process of determining optical identifications for the radio sources, which we use to classify star-forming galaxies and AGN. This provides a very large sample of radio AGN allowing us to study in detail the population of radio AGN and their host galaxies, out to redshifts of about 1.
Host: Alex Clarke |
| Oct 28 |
JBCA Colloquium
Prof. Alexandre Lazarian
(University of Wisconsin) |
Studying B-modes and B-fields: New Ways of Tracing and Probing Magnetic fields with Velocity and Synchrotron Gradients |
| Abstract: Modern understanding of MHD turbulence suggests that this type of turbulence is strongly anisotropic at small scales. Due to turbulent fast reconnection turbulent eddies are aligned with the magnetic field surrounding the eddies. This entails a conclusion that gradients of velocity and magnetic field are perpendicular to the local direction of the magnetic field. Guided by this fact we proposed, developed and successfully tested with observational data a set of new techniques for studying interstellar magnetic fields. I shall demonstrate how the velocity gradients can be measured using either velocity centroids of thin channel spectroscopic maps, while magnetic field gradients can be measured using synchrotron intensity or synchrotron polarization. I shall present 3D maps of galactic magnetic fields obtained with the new technique. I shall show the predictions of dust foreground polarization that are done with HI data using the velocity gradients.
Host: Clive Dickinson and Paddy Leahy |
| Oct 29 |
Special seminar
Prof. Alexandre Lazarian
(University of Wisconsin-Madison) |
Reconnection in realistic turbulent astrophysical environments |
|
Abstract: TBD |
| Nov 6 |
Schuster Colloquium
Prof. Dr. Thomas Klinger
(MPI for Plasma Physics) |
The long way to steady state fusion plasmas |
| Abstract: The stable generation of high temperature hydrogen plasmas (ion and electron temperature in the range 10-20 keV corresponding to about 100-200 million K) is the basis for the use of nuclear fusion to generate heat and thereby electric power. The most promising path is to use strong, toroidal, twisted magnetic fields to confine the electrically charged plasma particles in order to avoid heat losses to the cold, solid wall elements. Two magnetic confinement concepts have been proven to be most suitable: (a) the tokamak and (b) the stellarator. The stellarator creates the magnetic field by external coils only, the tokamak by combining the externally created field with the magnetic field generated by a strong current in the plasma. “Wendelstein 7-X” is the name of a large superconducting stellarator that goes into operation after 15 years of construction. With 30 m^3 plasma volume, 3 T magnetic field on axis, and 10 MW micro wave heating power, hydrogen plasmas are generated that allow one to establish a scientific basis for the extrapolation to a future fusion power plant. Wendelstein 7-X is designed to generate high-power hydrogen plasmas under steady-state conditions, more specifically for 1800 s duration (note that the world standard is now in the 10 s ballpark). This talk provides a review of the principles of nuclear fusion and discusses the key physics subjects of optimized stellarators. We summarize the adventurous undertaking to construct such a first-of-a-kind device as well as the most important findings during the first operation phases of Wendelstein 7-X. This concerns stable operation of high-performance plasmas for several 10 up to 100 s, stellarator record values for the combined value of density, temperature and confinement time, plasma impurity transport, and the controlled plasma-wall contact. We finish with an outlook towards the fusion power station and address the most important remaining issues in the framework of the worldwide fusion research endeavor.
Host: Jens Chluba |
| Nov 7 |
Special Seminar
Dr. Vanessa McBride
(South African Astronomical Observatory) |
Massive X-ray binaries and related systems |
| Abstract: The work I will present centres on understanding factors that influence the evolution of massive X-ray binaries. In this talk, I will focus on some of our recent attempts to understand the mass transfer mechanism in Be X-ray binaries, and take a broader look at how the X-ray binary population population is related to the population of radio pulsars with massive companions.
I will also discuss the Office of Astronomy for Development (OAD), which is an initiative of the International Astronomical Union that aims to use the skills, methodologies and inspirational power of astronomy to address socioeconomic development. The OAD has established several partnerships across the world including one with DARA Big Data based in Manchester. In this talk I will discuss the approach of the OAD, and explain some of the past and current projects.
Hosts: Tana Joseph & Ben Stappers |
| Nov 13 |
JBCA Colloquium
Dr. Anais Moller
(Universite Clermont-Auvergne) |
SuperNNova: Bayesian Neural Network light-curve classification for time-domain astronomy |
| Abstract: In this talk I will present some of the challenges in supernova cosmology currently addressed with machine learning. In particular, I will focus on supernova photometric classification which is becoming increasingly important to exploit current and future astronomical datasets like the Dark Energy Survey and LSST.
Here, I will present SuperNNova, an open source photometric classification framework that leverages the power of Recurrent Neural Networks. Using supernova simulations, we obtain classification accuracies >84% for events with a handful photometric observations and >96% for complete light-curves. Our algorithm is able to accurately classify multiple classes of supernovae within seconds. SuperNNova can be trained in a principled, Bayesian way and yield calibrated predictions with sensible uncertainty estimates. Using supernova cosmology as an example, I will discuss the impact of photometric classifiers and often neglected pitfalls of machine learning algorithms. I will emphasize the importance of properly calibrated classification probabilities and the additional information that provide epistemic uncertainties when dealing with representativeness issues and out-of-distribution events.
Host: Anna Scaife |
| Nov 20 |
JBCA Colloquium
Prof. Peter Gallagher
(Trinity College Dublin) |
The Shocking Radio Sun |
| 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.
Host: Philippa Browning |
| Nov 27 |
Schuster Colloquium
Prof. Gavin Salam
(University of Oxford) |
Colliders, Higgs and the strong interaction |
| Abstract: Particle colliders are our main laboratory tool to study the smallest distance scales accessible to humankind. Recent years have seen major advances, notably the discovery of long-hypothesised, but qualitatively new interactions in the Higgs sector, which are essential for a universe as we know it. Central to the progress of collider particle physics is our understanding of the strong interaction and its theoretical formulation, quantum chromodynamics. This rich theory operates across many orders of magnitude in distance and momentum, producing hundreds of particles in each collision. One of today's major challenges is to learn how to maximally and reliably exploit the resulting information.
Hosts: Terry Wyatt and Mrinal Dasgupta |
| Dec 4 |
JBCA Colloquium
Dr. Rebecca Bowler
(University of Oxford) |
Bright galaxies in the first billion years |
| Abstract: Studying galaxies at ultra-high redshifts (z > 6) provides a unique insight into the early stages of galaxy formation and evolution. I will give an overview of how star-forming ‘Lyman-break’ galaxies are selected in the first billion years, and what is known about their properties from multi-wavelength follow-up (e.g. from ALMA, Hubble). I will then show how samples of these objects can constrain the astrophysics at play in early galaxy formation through the observed shape and evolution of the luminosity function. I will end by looking forward to upcoming wide-area surveys from LSST and Euclid, which, when combined with 21cm neutral Hydrogen experiments, will constrain the progress and topology of Reionization.
Host: Ian Harrison |
| Dec 10 |
Special Seminar
Dr. Yiping Shu,
(IoA, Cambridge) |
An All-sky AGN Catalogue form Gaia and WISE |
| Abstract: Active galactic nuclei (AGNs) are compact cores in active galaxies that emit strong radiation over a broad wavelength range. Large samples of AGNs with wide sky coverage are of particular interest in astronomy and astrophysics. In this talk, I willintroduce a new, all-sky catalogue of AGN candidates selected from the latest data of two surveys -- Data Release 2 of the Gaia mission and the unWISE catalogue of the Wide-field Infrared Survey Explorer (WISE). Applying a random forest classifier to the Gaia-unWISEjoint sample, we identify 2,734,464 AGN candidates across the effective 36,000 sq. deg sky, of which 0.91 million are new discoveries. Cross-matching the AGN candidates with a sample of known bright cluster galaxies, we find a high-probability strongly-lensedAGN candidate with a large image separation of 21.06 arcsecs. All the AGN candidates in our catalogue will eventually have ~5-year long light curves from Gaia, and thus will be a great resource for AGN variability studies. Our AGN catalogue will also be helpfulin AGN target selections for future spectroscopic surveys, especially ones in the southern hemisphere.
Host: Neal Jackson |
| Dec 11 |
JBCA Colloquium
Dr. Andrew Tkachenko
(KU Leuven) |
Stellar astrophysics in the era of big data from space and the ground |
| Abstract: Stellar astrophysics has received a groundbreaking boost with the launch of space missions such as CoRoT and Kepler. To date, over 4 000 exoplanets have been discovered with a considerable fraction of those being in the super-Earth and Neptune mass-density regimes. In addition to that, ultra-high precision space photometry delivered by the above missions led to detection and discovery of a zoo of intrinsically variable stars. It has been found that irrespective of their evolutionary stage and mass, stars in their majority experience periodic quakes that get recorded with our instruments in the form of brightness variations at the surface of the star. Asteroseismology “inverts” frequencies, amplitudes, and phases of these brightness fluctuations into physical properties of inner regions these stellar oscillations originate from. With the help of asteroseismology, applied to CoRoT and Kepler data, we have learned that models of stellar evolution and interior structure are very much inferior to state-of-the-art observations and that they lack important physical ingredients. Currently operational TESS mission as well as the PLATO mission scheduled for launch in 2026, bring a new asset in stellar astrophysics through observing orders of magnitude bigger and homogeneous stellar samples across entire sky. Machine learning techniques applied to the above data become a vital ingredient in bridging high-quality observations and applied stellar astrophysics to calibrate and improve current theories of stellar structure and evolution. In this talk, I will provide a necessary introduction to Machine Learning in Astronomy as well as to asteroseismology as a powerful tool to probe deep stellar interiors otherwise inaccessible to any existing astronomical instrumentation. I will talk about asteroseismic community efforts to mind rich data sets of TESS and PLATO to provide automated light curve extraction and classification of light curves according to the type of variability encoded in them. Ultimately, I will present a few examples of potential immediate application of automated variability classification to an astrophysical problem.
Host: Rene Breton |
| Jan 29 |
JBCA Colloquium
Dr. Stewart Eyres
(University of South Wales) |
Nova sub capita Cygni |
| Abstract: In the early 1980s CK Vulpeculae was identified with Nova Vul 1670, a star that brightened from invisibility to 3rd magnitude nearly 350 years ago (the nova sub capita Cygni of the title). Initially of interest due to a proposed link with hibernating classical novae, the nature of the central stellar object remains unclear. In the literature various explanations have been discarded, including a classical nova outburst, a very late thermal pulse, a sub-Chandrasekhar mass supernova or a diffusion-induced nova. Most recently a stellar merger has been favoured, but various scenarios involving giant and main sequence components are difficult to reconcile with the observed characteristics. ALMA observations in 2017 resolved various structures in the gas and dust of the inner nebula, leading us to propose a new merger scenario. We argue that this best explains the observed activity in the 1670s, the current nebula structure and the peculiar isotopic abundance patterns.
Host: Albert Zijlstra |
| Feb 5 |
JBCA Colloquium
Dr. Rosita Kokotanekova
(ESO) |
Photometry of comet nuclei and other related populations of small bodies |
| Abstract: Jupiter-family comets (JFCs) are among the most intriguing objects in the Solar System. Traditionally, they are considered to be well-preserved planetesimals that have remained unchanged for billions of years in the outer Solar System and have therefore retainedkey evidence from the epoch of planet formation. However, we now know that JFCs have had a rich dynamical history which has taken them from planetesimals in the protoplanetary disk, through long residences as Trans-Neptunian objects (TNOs), followed by a migrationthrough the Centaur region between Jupiter and Neptune to become active or dormant comets making regular passes through the inner solar system. Since comet evolution is very closely related to the environment surrounding them, tracing the changes comets haveexperienced since formation is key for understanding the conditions in the outer Solar system throughout its history.
In the beginning of this talk, I will introduce the current understanding of the outer Solar System formation and evolution, highlighting the latest progress in this field driven largely by the two most recent space missions, Rosetta and NewHorizons. I will then proceed to discuss the key role of ground observations in addressing some of the remaining questions and I will present our recent results on comet and TNOs photometry.
Host: Rene Breton |
| Feb 7 |
Special Seminar
Dr. Ian Heywood
(University of Oxford) |
The MeerKAT radio telescope |
| Abstract: MeerKAT is a South African radio interferometer, and presently the most powerful telescope of its kind in the world. The large number of baselines and low system temperature L-band receivers routinely provide deep radio imaging with excellent sensitivity to low surface brightness features. The telescope was inaugurated in 2018 and has been delivering data to its users since then. I will provide an overview of the telescope, and results from some projects I have been involved in, including the MIGHTEE and ThunderKAT large survey projects, and a commissioning observations that targeted the Galactic Centre region.
Host: Tim O'Brien |
| Feb 12 |
Special Seminar
Dr. Moritz Munchmeyer
(Perimeter Institute) |
New techniques for fundamental physics with CMB and galaxy surveys |
| Abstract: Upcoming experiments such as the Simons Observatory, DESI and LSST probe the universe with extremely high resolution. This upcoming data provides us with great opportunities for fundamental physics, such as probing the initial conditions of the universe. However, the vastness and extreme complexity of this interrelated data requires new methods to make sense of it. I will describe two ways forward, one based on theoretical understanding and one based on computation. In the former, I show how CMB and galaxy data can be combined in a new way to give unprecedentedly tight constraints on aspects of primordial physics. In the latter, I describe a step towards performing precision cosmology with machine learning, in a way that builds on the powerful physical and statistical methodology that has led to the success of observational cosmology.
Host: Jens Chluba and Richard Battye |
| Feb 13 |
JBCA Colloquium
Dr. Yashar Akrami
(Ecole Normale Superieure) |
From de Sitter to Planck: Searches for new physics with Stage IV cosmological surveys |
| Abstract: In the era of precision cosmology, various large-scale cosmological collaborations have been formed with the ambitious objective of mapping the entire observable Universe. Not only has this provided us with detailed understanding of the Universe and its evolution, but it has also made it possible to search for new physics beyond our standard models of particle physics and gravity. This new physics is expected to show up at extremely high energies (close to the Planck scale) and/or extremely low energies (the scale of vacuum energy today), the two ends of the spectrum that can be probed by cosmic evolution at earliest and latest times, respectively. Cosmological observations, therefore, have played and will continue to play essential roles in developing fundamental theories, in the quest for understanding the nature of fundamental interactions and answering basic questions about the structure of spacetime.
In this seminar, I will review some of these unsolved fundamental questions, and will explain how they are expected to be answered in the coming years using the wealth of cosmological data that will be provided by a large number of upcoming surveys across all wavelengths in combination with future theoretical developments in cosmology and high energy physics. I will focus on the synergistic science that will be provided by Stage IV cosmological surveys, in particular Euclid, LiteBIRD and the Square Kilometre Array (SKA). I will also introduce a powerful machinery based on advanced inference techniques and artificial intelligence that is currently being developed and is expected to significantly facilitate searches for new physics beyond the standard frameworks.
Host: Aditya Rotti |
| Feb 19 |
Schuster Colloquium
Dr. Laura Fumagalli
(University of Manchester) |
Probing the dielectric constant on the nanoscale: from thin films to DNA and confined water |
| Abstract: In this talk I will first review our work in which we developed scanning probe microscopy techniques able to measure for the first time the dielectric constant (or permittivity) on the nanoscale. We applied these techniques to study a variety of bio and non-bio materials - from thin films and nanoparticles to bacteria and macromolecules such as DNA - either in dry or liquid environment. I will then present our most recent work in which we addressed the case of the anomalous dielectric constant of water confined near surfaces, a scientific question that has vexed the scientific community for many decades. It was speculated that the dielectric constant of water near surfaces should be different from that of bulk water. This effect has major implications in many disciplines, from physics, geophysics and surface science to chemistry and molecular biology, because water’s dielectric constant directly affects various forces between micro-objects and macromolecules. In turn, those forces define many phenomena around us. Our experiments on water-filled nanochannels made of van der Waals crystals revealed the presence of an interfacial water layer with vanishingly small polarization. The electrically dead layer was found to be two-to-three molecules thick, in good agreement with molecular dynamics calculations. Our findings provide much needed feedback for theories describing water-mediated surface interactions, and show a way to investigate the dielectric properties of other fluids and solids under extreme confinement.
Hosts: Steve Watts and Jens Chluba |
| Feb 26 |
JBCA Colloquium
Dr. Kaustuv Basu
(Argelander Institute, Bonn) |
CCAT-prime and the quest for SZ effect spectral distortions |
| Abstract: The first blind detection of galaxy clusters with the Sunyaev-Zeldovich (SZ) effect was reported in 2009, and in merely one decade, the number of SZ-selected clusters has crossed two thousand. The current generation of CMB experiments are moving ahead with this tremendous success of doing cosmology with SZ-selected clusters, and at the same time, opening up the possibility to extract science from the multi-wavelength analysis of SZ effect spectrum. These new science frontiers include modelling cluster temperatures directly from the relativistic corrections of the thermal SZ effect, and separating the contributions from much fainter variants of the SZ effect, such as the kinematic and nonthermal SZ effects. In my talk I will present the motivations and some recent results from our studies of the SZ effect spectral distortions, spurred by the participation of our group in the CCAT-prime collaboration. The talk will conclude with an overview of the science goals, instrumentation, and observation plans for this new CCAT-prime telescope.
Host: Mathieu Remazeilles and Jens Chluba |
| Mar 4 |
JBCA Colloquium
Prof. Dr. Thomas Janka
(Max Planck for Astrophysics, Garching) |
3D Core-Collapse Supernova Modeling:
Connecting Progenitors to Supernova Outcomes |
| Abstract: Neutrinos have long been thought to trigger and power the
majority of supernova explosions of massive stars. This theoretical idea is now supported by 3D neutrino-hydrodynamical simulations. The progress was made possible by advances in supercomputer modeling, upgrades of the complex microphysics in hot neutron stars, and a better understanding of the processes that affect the final stages of stellar evolution. Although a direct confirmation of the theory will require measurements of neutrinos and gravitational waves from a Galactic supernova, numerical models are advanced enough now to make predictions for observable astronomical phenomena. The talk will provide an overview of the status of our theoretical understanding of core-collapse supernovae, the efforts to link models to observations, and the still open questions.
Host: Jens Chluba |
| Mar 11 |
[CANCELLED] JBCA Colloquium
TBA
(TBA) |
[CANCELLED due to strike] |
| Abstract:
Host: |
| Mar 18 |
[POSTPONED] Bragg Lecture
Dr. Tamsin Edwards
(King’s College London) |
[POSTPONED] What fate for the Antarctic ice sheet? |
| Abstract: Antarctica is a distant, unfamiliar place. We hear of ice shelves collapsing, giant icebergs breaking away, glaciers crumbling: but how much we do know about the fate of this great ice sheet? I will talk about my research in quantifying uncertainty in Antarctic ice sheet projections, using methods such as Bayesian calibration and statistical ‘emulation’ of computer models, and how this has been used in evidence reviews for policymakers such as the IPCC assessment reports.
Hosts: Jeffrey Forshaw and Jens Chluba |
| Mar 25 |
[CANCELLED] JBCA Colloquium
TBA
(TBA) |
[CANCELLED due to Covid-19] |
| Abstract:
Host: |
| Apr 1 |
JBCA Virtual Colloquium
Prof. Sarah Bridle
(University of Manchester) |
Change your diet: the easiest way to help reduce your climate impact |
| Abstract: I have been studying dark matter and dark energy for the last 20 years, but when my kids started school I started to think about our own planet in the next 20 years and beyond. I learned about climate change properly for the first time, how it threatens worldwide food production, and how food causes about a quarter of all global warming. I wanted to know how much each of my food choices was contributing, and why. I delved into the academic research literature, and summarized the results in simple charts. The charts make it easy for the non-specialist to see the impacts of different meal options, and show that some easy food switches can reduce food greenhouse gas emissions by 90 percent. Most of us make many food choices every day, and by changing these we can significantly reduce climate change caused by food, and free up land that can be used to help reduce climate change overall.
Zoom link: https://zoom.us/j/218726100 |
| Apr 15 |
JBCA Virtual Colloquium
Dr. Eamonn Kerins
(University of Manchester) |
Exoplanet science in an era of explosive growth |
| Exoplanet science is going through a period of explosive growth. Currently there are
around 4,000 detected planets and this is set to grow to around 40,000 over the next
decade. I will discuss some of the work ongoing at Manchester that is shaping the
design of some of the next-gen surveys and that will also help us to keep pace with the
expected growth in data. At Manchester we are studying cold exoplanet demographics
through microlensing. We have developed MaBuLS - a World-leading simulator that is
being used to shape the exoplanet science strategy of the NASA WFIRST mission and
potentially an ESA Euclid additional science programme. The exoplanet community is also
now moving from exoplanet detection to characterisation, including studying the
atmospheres of exoplanets. Over the next decade we will progress from dozens to
thousands of potential targets for atmospheric characterisation thanks to the TESS and
PLATO missions. SPEARNET is a new Manchester-NARIT collaboration that is developing an
automated target selection and reduction pipeline for exoplanet atmosphere studies
undertaken within a distributed heterogeneous telescope network. SPEARNET is a
demonstrator for how a globally-distributed network of telescopes can be deployed to
maximise the science when the number of available targets vastly exceeds available
follow-up resources.
Zoom link: https://zoom.us/j/218726100 |
| Apr 23 |
JBCA Colloquium
Dr. Tanmoy Laskar
(University of Bath) |
GRBs: The Radio Revolution |
| Abstract: Gamma-ray bursts, the most energetic explosions in the Universe, are ideal probes of extreme relativistic astrophysics. Thanks to their great luminosities, they illuminate our understanding of the emergence of the first light in the Universe, while providing a unique laboratory for the study of relativistic shock physics. Observing and modeling their radiation provides crucial clues to our understanding of particle acceleration in relativistic shocks, explosion and jet launching mechanisms, and the characteristics of GRB progenitors, which together inform our ability to use GRBs as probes of the cosmic dawn to the highest redshifts. I argue how radio followup observations are beginning to yield a wealth of information about each of these aspects, and present results of our on-going campaign to obtain unprecedented spectral and temporal coverage of GRB afterglows with a range of facilities, including the Jansky VLA, ALMA, ATCA, and GMRT. I conclude by demonstrating the power of radio observations in uncovering unexpected, and inexplicable new phenomena and a look to the future of radio observations of energetic transients.
Host: Manisha Caleb |
| Apr 27 |
Special Seminar
Philippa Sarah Cole
(University of Sussex) |
Primordial black holes and how to produce them |
| Abstract: Primordial black holes have had a recent surge in popularity due to the LIGO/VIRGO detections and the possibility that they could make up all or part of the dark matter. However, even if you only want to produce one primordial black hole, there are tough requirements for the inflationary potential which can be translated into constraints on the primordial power spectrum. I will show that there is a limit to how fast the power spectrum can grow, and how constraints due to spectral distortions, primordial gravitational waves and 21cm observations are getting closer and closer to ruling out primordial black holes on certain mass ranges.
https://us02web.zoom.us/j/84330484071
Host: Jens Chluba |
| Apr 29 |
JBCA Virtual Colloquium
Prof. Steve Eales
(Cardiff University) |
Submillimetre Astronomy Then and Now |
|
Abstract:
In the first two thirds of the seminar, I will describe some of the big discoveries made with the Herschel extragalactic surveys. I will start by showing how the thousands of lensed systems discovered with Herschel have huge potential for measuring cosmological parameters and for investigating the formation of galaxies. I will then show how the Herschel results suggest that the paradigm that galaxies fall in two distinct classes - star-forming galaxies and passive galaxies - is wrong. I will propose an alternative model for galaxy evolution, in which the properties of galaxies lie on a single continuum, and the catastrophic quenching process needed to explain the existence of two classes is replaced by weaker evolutionary processes. In the final third of the talk I will discuss some of my group's current projects, including the Extreme Galaxy Project (an attempt to do for the submm waveband what 3C did for the radio), a project to produce the first atlas that shows how the properties of dust vary over a galaxy, and the discovery of a high-redshift protocluster. I will finish by discussing the future of submm astronomy in the UK.
Host: George Bendo |
| Apr 29 |
[POSTPONED] Schuster Colloquium
Dr. Sudeep Das
(Netflix) |
[POSTPONED] |
| Abstract: N/A
Hosts: Jens Chluba |
| May 6 |
[POSTPONED] JBCA Colloquium
Dr. Shari Breen
(SKA) |
[POSTPONED] |
| Abstract: [POSTPONED]
Host: Keith Grainge |
| May 13 |
[POSTPONED] JBCA Colloquium
Dr. Mariangela Bonavita
(The University of Edinburgh) |
[POSTPONED] |
|
Abstract: [Due to unforeseen circumstances, this colloquium has been postponed]
Host: Rene Breton |
| May 20 |
JBCA Virtual Colloquium
Prof. Kiyoshi Masui
(MIT) |
A Synoptic View of Fast Radio Bursts with CHIME |
|
Abstract: The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is the only radio telescope capable of instantaneously observing hundreds of square degrees with the sensitivity of a 100-meter scale aperture. As a result, its transient search instrument, CHIME/FRB, has detected roughly 700 fast radio bursts (FRBs) in its first year of full operations---increasing the known sample by an order of magnitude. CHIME/FRB thus represents a new era in the study of these enigmatic, extragalactic radio flashes and presents opportunities to use them as probes of the Universe. I will show how CHIME's novel, digitally-driven design, coupled with the availability of mass-produced analogue and digital hardware, has enabled this leap in telescope capabilities. I will then give an overview of CHIME/FRB's most recent results and conclude by describing efforts to augment CHIME's capabilities by adding outrigger telescopes. These outriggers will be located across the continent and will precisely localize FRB sources using very long baseline interferometry.
Zoom link: https://zoom.us/j/218726100
Host: Jens Chluba and Laura Wolz |
| May 27 |
JBCA Virtual Colloquium
Dr. Anna Francesca Pala
(ESO) |
A Gaia DR2 insight into the Galactic population of cataclysmic variables |
| Abstract: Cataclysmic variables (CVs) are close interacting binaries containing a white dwarf accreting from a late-type star. CVs are the best-suited laboratories in which to test the models of compact binary evolution as they are numerous, relatively bright, and both stellar components are structurally simple. A large and well-defined sample of CVs is fundamental to study the global properties of such stars and to critically test our understanding of the evolution of all types of binaries. However, until recently, all available CV samples were affected by strong selection biases. Only the advent of the second data release (DR2) of the ESA mission Gaia has offered the unique opportunity to construct a volume-limited sample of CVs that can provide accurate constraints on the properties of their Galactic population. In this talk, I present the study of the 150 pc CV sample to accurately constrain their space density, the composition of the intrinsic population as well as the white dwarf mass and effective temperature distributions. Being largely free of selection biases, the results of this study represent one of the most accurate and reliable tests of the current models of binary evolution.
Host: Mark Kennedy |
| Jun 3 |
JBCA Colloquium
Dr. Tessa Baker
(QMUL) |
Testing Gravity with Gravitational Waves |
|
Abstract: Gravitational waves (GWs) have already proved immensely powerful for constraining cosmological extensions of GR, both from data-driven and theoretical perspectives. However, GWs really come into their own when used in combination with complementary electromagnetic data. I’ll review some of the latest bounds on modified gravity from GWs, and look at how the remaining gravity parameter space can be tested with future experiments like LISA and accompanying galaxy surveys.
Host: Ian Harrison |
| Jun 12 |
JBCA Colloquium
Dr. Evan Keane
(SKAO) |
Cosmology with Fast Radio Bursts |
| Abstract: Fast Radio Bursts are a booming industry. So fashionable is
the study of FRBs that new telescopes have been built, and existing
telescopes refurbished, specifically to find them. All of this
activity has increased their discovery rate from ~1/year to ~1/day. As
the field enters its teenage years, astronomers are sure that they
exist. The sample is becoming sufficient to address important
questions such as (a) what are their progenitors? and (b) what are
they good for? In this talk I will consider both of these questions, paying particular attention to
the latter. The field of FRB cosmology is just emerging and I will
describe some of the scientific potential and the various pitfalls
that may arise. Further, I will describe some of the 'foreground'
studies that must also be undertaken if it is to reach levels of
precision and impact comparable to the likes of WMAP and Planck.
Host: Manisha Caleb & Ben Stappers |
| Jun 17 |
JBCA Colloquium
Dr. Daan Meerburg
(University of Groningen) |
Towards a detection of primordial non-Gaussianity |
| Abstract: In a period of 40 years, observational cosmology has transformed from backyard science led by a small number of people into huge experimental efforts, counting sometimes thousands of members. While early experiments were able provide breakthrough discoveries with limited man power, today these large collaborations are required because we are reaching the limits of our experimental capacity. Although challenging, new cosmological observations could still provide us with monumental discoveries. One of the more illustrative observables is primordial non-Gaussianity. I will explain the relevance of this observable for early Universe cosmology. I will then discuss how we hope to go beyond current constraints set by the Planck satellite with future measurements of the cosmic microwave background. I will discuss limitations and provide potentially new ways to reach theoretically compelling thresholds this decade. Whilst the CMB will eventually run out of modes, the large scale structure of the Universe will be the next frontier to constrain the physics of the early Universe. I will present some work that utilizes a clever trick to constrain primordial non-Gaussianity using tracer bias and so-called cosmic variance cancellation. This method has the potential to reach constraints that are an order of magnitude better than current constraints. In this work we achieve this cancellation with only a single tracer by first reconstructing the large scale mode using only small scales.
Host: Jens Chluba |
| Jun 24 |
JBCA Colloquium
Prof. Dimitrios Giannios
(Purdue University) |
TBD |
| Abstract: TBD
Host: Jens Chluba |
