Arif Babul
Title: The Formation and Evolution of Massive Galaxies in the Cosmos and their Circumgalactic Environment
Contrary to many stereotypes about massive galaxies, the observed systems are diverse in their star formation rates, kinematic properties, and morphologies. Studying how they evolve into and express such diverse characteristics is an important piece of the galaxy formation puzzle. Here, we focus on a subset of massive galaxies, the brightest group galaxies (BGGs). We use a high-resolution cosmological suite of simulations based on the Romulus galaxy formation model, and compare simulated central galaxies in group-scale halos at đ§ = 0 to their observed counterparts. Since most galaxy formation models are calibrated using measures that are strongly influenced by the properties and evolution of ânormalâ Milky-Way like galaxies, this exercise is also an opportunity to test the limits of these models. The comparison encompasses the stellar mass-halo mass relation, various kinematic properties and scaling relations, morphologies, and the star formation rates. We find Romulus BGGs that are early-type S0 and elliptical galaxies as well as late-type disk galaxies; we find BGGs that are fast-rotators as well as slow-rotators; and we observe BGGs transforming from late-type to early-type following strong dynamical interactions with satellites. In short, we find that Romulus reproduces the full spectrum of diversity in the properties of the BGGs very well. Additionally, due to its superb mass and spatial resolution, Romulus also offers a unique window onto the joint evolution of the BGGs and the surrounding intragroup medium. With respect to the latter, we are able to observe the emergence of multiphase structure – in the form of cold clouds – in the intragroup medium. Groups also experience repeated AGN feedback episodes that drive large-scale collimated outflows into the IGrM. While the present resolution does not allow direct exploration of the coupling between the clouds and the AGN jets, we argue that the clouds will cause the SMBHs (and hence, the jets) to change direction every so often. Returning back to the BGGs, we find that early type galaxies can rejuvenate by growing disks, in agreement with recent observations. However, we also note a tendency towards lower than the observed fraction of quenched BGGs, with increasing halo mass. The problem appears to be due to decreasing effectiveness of AGN feedback with increasing halo mass. Examining some of the other galaxy formation models, we find that they too run into trouble on the same scale â but in an opposite sense. I will conclude by discussing what we are to make of this and what the path forward looks like.
Richard Parker
Title: The origin of short-lived radioisotopes in the Solar System
Some of the oldest objects in the Solar System contain the decay products of two short-lived radioisotopes (SLRs), 26-Al and 60-Fe. These SLRs are much more abundant in the early Solar System than in the Interstellar Medium (ISM), suggesting that the Sun (and its protoplanetary disc) was either enriched in SLRs early in its life, or formed from material that was already enriched to levels in excess of the ISM. In this talk, I will discuss the origin of these SLRs, and the pros and cons for the various theories that explain how 26-Al and 60-Fe ended up in the Solar System.
Marie Martig
Title: The structure of thick discs in nearby galaxies
Thick disks are ubiquitous in nearby spiral galaxies, and many mechanisms have been proposed to explain their formation. I will show how, in simulated galaxies, thick disks arise from the superposition of mono-age populations (MAPs). I will discuss the connection between the properties of the MAPs and the global structure of thick disks, in particular their shape and their radial age gradient. I will also show how this can be linked with a galaxyâs recent merger history: mergers create gaps in the vertical structure of MAPs, and give rise to thick disks that are clearly distinct from thin disks. I will finally present results on the age structure of the Milky Way and a few nearby galaxies. I will end the talk with an introduction to the GECKOS survey, a new VLT/MUSE large programme targeting 35 nearby edge-on galaxies.
Lyndsay Fletcher
Title: Solar Chromospheric Flares
A solar flare is an intense but short-lived release of energy from the Sun’s magnetically-dominated atmosphere. Flares result in the acceleration of non-thermal particles embodying possibly 50% of the energy released, plus plasma heating, mass motion and radiation across the entire electromagnetic spectrum, which comes mostly from the chromosphere. The central questions in solar flare physics are: how is magnetic energy that was stored in the coronal magnetic field released and converted into other forms, and how is it transported and dissipated in the chromosphere giving rise to the flare signatures that we observe? In this talk I will overview the basic observations and framework of a solar flare before focussing on its development in the solar chromosphere. In recent years solar physics has benefited from a glut of glorious multi-wavelength images and spectroscopy, and I will show how chromospheric observations, particularly made at high spatial and temporal resolution are used to constrain important aspects of the flare chromosphere and flare physics.
Fasil Dejene
Title: Interplay between charge, spin, super and heat Currents in 2D and 3D Materials
Unwanted heat generation from the flow of electrons is often considered a limitation for the proper functioning of electronic devices. Nevertheless, this waste heat can be utilised to develop spintronic devices that employ heat for read/write operations or to efficiently regulate heat flow using magnetic heat valves. This functionality can be powerful when integrating two-dimensional (2D) materials with spin caloritronic principles. In this talk, I will explore the interaction between charge, spin, and heat currents, drawing insights from thermoelectrics, which involve charge-heat coupling, and from spintronics, which focuses on charge-spin coupling. The unique properties of 2D materials, such as high carrier mobility, tunable bandgaps, and strong spin-orbit coupling, make them ideal candidates for spin-orbit torque engineering, which is challenging to achieve in traditional systems.
Next, I present new results on innovative methods for generating and detecting spin currents in 2D materials, as well as on picosecond magnetoacoustics in yttrium iron garnet systems. I will also introduce and discuss the concept of magnetic heat valves, which operate similarly to giant magnetoresistance (GMR) devices but are specifically designed for controlling the heat flow in spin-caloritronic applications.
Charlotte Kestner
Title: How to Outreach: a multidisciplinary, cross faculty module in outreach
In âHow to Outreachâ undergraduate students get the opportunity to try their hand at designing and delivering an outreach activity for primary aged students (usually year 5 or 6). The students are drawn from across the university and bring their subject expertise together in multi-disciplinary groups. In this seminar I will describe the different aspects of this module and discuss the challenges associated with it.
Derek Ward-Thompson
Title: Latest Results From The JCMT BISTRO Survey – Can B-fields explain why star formation is so inefficient?
The submillimetre continuum emission from dust grains is polarised because the grains tend towards alignment perpendicular to B-field lines. For asymmetric particles with some ability to be magnetized, a series of relaxation processes brings the grains towards their lowest energy rotation state. This is with the longest axis perpendicular to the field. We are currently using this method to measure the B-field orientation in numerous Galactic star-forming regions in a large-scale project on the JCMT known as BISTRO (B-fields In Star-forming Region Observations). The BISTRO Project overall is comprised of three Large Programs, BISTRO-1, 2 & 3, which were each awarded 224 hours of Band 1 & 2 weather with SCUBA-2 and POL-2. This talk reports on progress in all three projects together, specifically addressing the issue of star-forming inefficiency, and why star formation in our Galaxy and other galaxies appears to occur ten times slower than free-fall. Can B-fields explain the discrepancy?
Dan Johnson
Title: The Thermodynamic Response of Heating at Coronal Null Points
Magnetic null points are an important component of coronal magnetic fields and can be sites of enhanced dissipation and, therefore, heating. In this presentation, I will discuss the plasma structure around a heated magnetic null point and support this with analytical and numerical models. We will see that the temperature profile, about a null, not only differs significantly from that in a uniform field, but also that the profile depends strongly on the spatial structure of the heating. Field lines close to the separatrices and the null point have higher temperatures than a uniform field for the same heating input. A comparison between analytical and numerical solutions is presented and the limitations of numerical approaches is discussed.
David Sands
Title: Towards a theory of science education: the role of thinking and reasoning
It seems somewhat obvious to say that meaningful learning requires that students think about and reason with the information they are given, but faced with obvious failures to reason either correctly or, in some cases, not at all, the question of how to promote reasoning arises. It is clear from research in psychology conducted over many years that humans are susceptible to all sorts of information processing biases and frequently demonstrate faulty reasoning. In students, this might result in, among other things, the formation of misconceptions, the apparent failure to correct misconceptions, even when a correct explanation is available and has been taught, and a willingness, perhaps even a desire, to put rote learning ahead of the development of a coherent view. The literature is replete with accounts of active techniques intended to promote deeper learning, but these are empirical and not all are completely successful or appreciated by all students. Can a theory of learning be constructed that will account for these and other difficulties? It has been my goal for the last 20 years to understand the cognitive processes involved in learning and practising physics and in this talk I will put forward the essence of a theory of education based on current ideas on thinking and reasoning. Many of the ideas already exist in the psychology literature, but whereas they are regarded as separate topics or areas of research within that discipline, it is my contention that they are linked and should be considered together. Although my own discipline of physics forms the backdrop to my research, the theory is not specific to physics. It is a general theory that can not only shed light on some puzzling features of student learning, as described above, but can also inform teaching practice. Examples from my own teaching and research will be highlighted.
Ben Robinson
Title: Quantum interference enhanced transport properties in molecular-scale junctions for thermoelectric application
Room-temperature quantum interference (QI) can be used to enhance the thermal and electrical properties of arrays of organic molecules to create ultra-thin-film thermoelectric materials with an unprecedented ability to convert waste heat to electricity using the Seebeck effect and to cool at the nanoscale via the Peltier effect.
The realisation of self-assembled molecular-electronic films, whose room-temperature transport properties are controlled by quantum interference (QI), is an essential step in the scale-up of QI effects from single molecules to parallel arrays of molecules. Here I will report on our recent progress such enhanced self-assembled monolayers (SAMs). I will focus on experimental aspects of the work using and discuss the key role that scanning probe microscopy takes in the characterisation of SAMs.
Recently, the effect of destructive QI (DQI) on the electrical conductance of self-assembled monolayers (SAMs) has been investigated. Here, I will show that we have demonstrated chemical control of different forms of constructive QI (CQI) in cross-plane transport through SAMs and its influence on cross-plane thermoelectricity in SAMs. It is known that the electrical conductance of single molecules can be controlled deterministically by chemically varying their connectivity to external electrodes. Here, by employing synthetic methodologies to vary the connectivity of terminal anchor groups around aromatic anthracene cores, and by forming SAMs of the resulting molecules, it can be clearly demonstrated that this signature of CQI can be translated into SAM-on-gold molecular films [1].
Furthermore, I will discuss the role that the chemical anchor of the SAM plays in the transport properties of the film [2] and how thermoelectric power harvesting can be controlled by the pressure applied to molecular junctions [3]. Finally, I will discuss the role of âslipperyâ porphyrin anchors [4] and multilayer films and how these offer exciting design strategies for future SAMs.
1. Wang, et al. Scale-Up of Room-Temperature Constructive Quantum Interference from Single Molecules to Self-Assembled Molecular-Electronic Films, Journal of the American Chemical Society 142 (19) 8555â8560 (2020)
2. Ismael, et al. Tuning the thermoelectrical properties of anthracene-based self-assembled monolayers, Chemical Science, 11, 6836-6841 (2020)
3. Wang, et al. Optimised power harvesting by controlling the pressure applied to molecular junctions. Chemical Science 12 (14), 5230-5235 (2021)
4. Wang, et al Thermoelectric properties of organic thin films enhanced by Ď-Ď stacking. Journal of Physics: Energy, 4 (2), 24002 (2022)
David O’Ryan
Title: Mapping Galaxy Morphology Across Dense Galactic Environments
Galaxy morphology â the shape, size and internal structure of a galaxy â provides key insights into the galaxies properties. These include any ongoing star formation, their merger history and ongoing secular processes. However, this relationship becomes more complex in the dense environments of massive galaxy clusters. Here, the intracluster medium strips infalling galaxies of their gas and harassment and merging by other cluster members drive morphological transformations.
To fully understand this, we require a large representative sample of various galaxy morphologies across clusters of varying mass, size and richness. In this talk, I will discuss using machine learning techniques with the novel ESA Datalabs platform to create such a sample. Morphology classifications of greater than 500,000 sources across 221 different clusters in the Hubble Legacy Archive are made. I will make an initial exploration of this catalogue focused on the evolution of galaxies hosting a central bar.
Donald Kurtz
Title: Asteroseismology
In 1926 in the opening paragraph of his now-classic book, The Internal Constitution of the Stars, Sir Arthur Eddington lamented, âWhat appliance can pierce through the outer layers of a star and test the conditions within?â While he considered theory to be the proper answer to that question, there is now an observational answer: asteroseismology. We are in a time of a significant advance in our understanding of stellar astrophysics with data from the Kepler and TESSSpace Missions. These have improved our ability to see pulsations and variability in stars by 100 to 1000 times compared with ground-based telescopes, allowing us to probe stars using asteroseismology. Astrophysics that used to be theoretical is now also observational, e.g. stellar internal stellar rotation from core to surface and the new tri-axial and single-sided pulsators in close binary stars. This talk will introduce the concepts of asteroseismology and show a selection of exciting new observational results.
Andrew Blain
Title: WISE, Aliens and Very Luminous Galaxies
People have been looking for âDyson Spheresâ â intelligent civilizations mining the energy output from their Sun. While this seems fanciful, and claims to detections are definitely incorrect, it is beyond the realm of science fiction. If aliens are dumb enough to let us see them at work, then the results from the WISE all-sky survey imposes tight limits on the numbers/lifetime of such worlds. More interestingly, âDyson Sphereâ dwellers can hide from us at a reasonable level relatively easily, but they are not immune to concerted investigation exploiting gravitational lensing.
Alison Young
Title: Planet formation and the youngest protoplanetary discs
Observations of protoplanets in their natal discs and measurements of disc masses indicate that planet formation must start soon after protoplanetary discs form. Early in their lifetime, discs are more massive and have different structures to the more evolved discs that are more frequently observed. Young protoplanetary discs may develop spiral arms driven by gravitational instability and may fragment. I will outline the physics we need to consider for modelling early disc evolution and introduce our recent developments. The new simulations present us with a revised picture of the youngest discs and their contribution to the beginnings of planet formation. I will share our latest results and discuss the implications for the theoretical view of planet formation. Finally, I will propose some possibilities for future exploration of the unanswered questions and for the observational verification of these ideas.
Victor Debattista
Title: Hints of bar growth from bulges and density profiles
Bars have long been predicted to be slowing down by transferring angular momentum to their dark matter halos, and in the process growing. While this predicts that bars are slowly rotating, the number of actually slow bars known is very low. Bars in massive galaxies also form boxy/peanut-shaped bulges. Although B/P bulges have long been observed, their formation does not require the bar to slow down to form, but become more prevalent in slow bars. So do bars actually slow down? In this presentation I discuss observational evidence that bars are growing, and therefore necessarily slowing down. I will also present new results on the formation of B/P bulges from the Illustris TNG50 simulation that informs our understanding of how B/P bulges form, and what it means for bar formation and evolution.
Timo Laitinen
Title: Early Propagation of Solar Energetic Particles in Turbulent Heliosphere
Solar energetic particles (SEPs), accelerated at or near the Sun, are typically observed with in situ instruments in the interplanetary space. As they arrive at Earth, they cause hazard to humans and technology in space and for high-latitude aviation. Because of this Space Weather risk, it is important to understand the origin and propagation of SEPs through the heliosphere. SEPs propagate in the turbulent solar wind plasma environment, and their motion is affected by the interplanetary magnetic field, which consists of a Parker spiral field that is superposed with turbulent fluctuations. The propagation of SEPs in this configuration is typically described as diffusion, within the framework of Fokker-Planck -type transport equations. In this talk, I review our recent advances that have shown that the diffusion-based approach is problematic particularly at the early stages of an SEP event. I will discuss the implications of these findings on SEP observations, and how the new multi-spacecraft observations of SEPs can improve our understanding of SEPs in the heliosphere.
ZdenÄk Prudil
Title: Tracing the Galactic Bar with Bulge RR Lyrae Stars
The Galactic bar is a key driver of the Milky Way’s internal evolution, redistributing stars and gas, influencing the structure of the central bulge. Understanding how different stellar populations interact with the bar helps unravel the Galaxy’s formation history. I analyze the RR Lyrae population toward the Galactic bulge to investigate its spatial and kinematic connection to the bar. RR Lyrae stars, as old, metal-poor standard candles, provide a unique view into the early Galaxy. By refining reddening maps and extinction laws from visual to near-infrared bands, I derive accurate distances that remove bar-like artefacts caused by extinction law variations. I find that only metal-rich RR Lyrae stars align spatially with the bar, while metal-poor stars form a more spheroidal distribution. For 8456 stars with full kinematics, I compute orbits in a Milky Way-like potential, revealing that prograde motion dominates among metal-rich stars, whereas metal-poor ones exhibit an increase in the retrograde orbits. These retrograde stars have stable orbital frequencies and are highly concentrated toward the Galactic center. Comparisons with N-body+SPH simulations suggest that such a structure can emerge through secular evolution without invoking a classical bulge.