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IoA Institute of Astronomy Talk Lists

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This is a List of Talks Lists that is a List of all IoA Seminars, Colloquia, Extra talks, IoA Stellar Pops and Extragalactic Gathering, etc. It is used as a feed for the IOA website and Digital Display screens. Individual Talks should NOT be added to this Talk lists. They should be added to one of the series that feed this list.
URL: https://talks.cam.ac.uk/show/index/13724
Updated: 40 min 51 sec ago

Tue 10 Jun 16:00: From Squiggles to Signals: Learning Useful Representations for Discovery in Time-Domain Astronomy

Mon, 09/06/2025 - 09:44
From Squiggles to Signals: Learning Useful Representations for Discovery in Time-Domain Astronomy

New large-scale astronomical surveys are observing orders of magnitude more sources than previous surveys, making standard approaches of visually identifying new and interesting phenomena unfeasible. Upcoming surveys such as the Vera Rubin Observatory’s Legacy Survey of Space and Time (LSST) and ongoing surveys such as the Transiting Exoplanet Survey Satellite (TESS) have the potential to revolutionize time-domain astronomy, providing opportunities to discover entirely new classes of events while also enabling a deeper understanding of known phenomena. The opportunity for serendipitous discovery in this domain is a new challenge that can be made systematic with data-driven methods, which are particularly suitable for identifying rare and unusual events in large datasets. In this talk, I’ll explore the potential for anomaly detection and representation learning in big datasets, and describe the challenge of applying these methods to real-time surveys. I’ll present novel machine learning methods for automatically detecting anomalous transient events such as kilonovae and peculiar supernovae, and characterising variable stars. I’ll explore the challenge of developing representative latent spaces useful for downstream machine learning tasks and present a novel causally-motivated foundation model. I’ll apply the approach to transients from the Zwicky Transient Facility (ZTF) and simulations of variable stars while discussing applications to upcoming surveys.

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Fri 20 Jun 11:30: Title to be confirmed

Fri, 06/06/2025 - 17:09
Title to be confirmed

Abstract not available

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Mon 16 Jun 16:00: Novel Approaches to Black Hole Ringdown Fits

Wed, 04/06/2025 - 10:23
Novel Approaches to Black Hole Ringdown Fits

Following a merger, a perturbed black hole relaxes into its final Kerr state, in part by radiating quasinormal modes (QNMs) — oscillations with specific complex frequencies and angular structures predicted by black hole perturbation theory. QNMs are widely used in waveform modelling and underpin key tests of general relativity and the nature of compact objects, though challenges remain, particularly in avoiding overfitting through well-motivated mode selection. In this talk, I will introduce new techniques for detecting and analysing QNMs, including spatial mapping, which extracts their angular structure, and a fast Bayesian fitting approach that models numerical relativity noise with Gaussian processes, providing a robust alternative to least-squares methods. I will present results obtained using the latest high-fidelity Cauchy-characteristic evolution (CCE) simulations by the SXS collaboration and show how these methods provide insight into the role of overtones and nonlinear effects, both of which will be important for future gravitational wave observations.

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Tue 10 Jun 13:00: The Response and Observability of Exo-Earth Climates to Cometary Impacts

Wed, 04/06/2025 - 10:01
The Response and Observability of Exo-Earth Climates to Cometary Impacts

Impacts by icy bodies likely played a key role in shaping the composition, and habitability, of Solar-System planets. We determine the role they may play in exoplanetary systems by coupling a cometary impact model with a 3D, Earth-analogue, climate model. I will discuss how both the impact-delivered water and thermal energy affects the global climate and composition, including: i) a modified cloud greenhouse effect and planetary albedo, ii) an enhancement in the abundance of most oxygen-bearing molecules (bar ozone), and iii) an enhancement in the escape rate of hydrogen from the exosphere. I will describe how these responses are shaped by atmospheric circulations driven by the planetary orbital configuration, including the role that impact location plays in setting the vertical transport and hence hydrogen escape rate. Finally, I will quantify the potential observability of individual massive impacts in future observations of exo-Earths.

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Tue 10 Jun 16:00: From Squiggles to Signals: Using AI for Discovery in Time-Domain Astronomy

Tue, 03/06/2025 - 15:09
From Squiggles to Signals: Using AI for Discovery in Time-Domain Astronomy

New large-scale astronomical surveys are observing orders of magnitude more sources than previous surveys, making standard approaches of visually identifying new and interesting phenomena unfeasible. Upcoming surveys such as the Vera Rubin Observatory’s Legacy Survey of Space and Time (LSST) and ongoing surveys such as the Transiting Exoplanet Survey Satellite (TESS) have the potential to revolutionize time-domain astronomy, providing opportunities to discover entirely new classes of events while also enabling a deeper understanding of known phenomena. The opportunity for serendipitous discovery in this domain is a new challenge that can be made systematic with data-driven methods, which are particularly suitable for identifying rare and unusual events in large datasets. In this talk, I’ll explore the potential for anomaly detection and representation learning in big datasets, and describe the challenge of applying these methods to real-time surveys. I’ll present novel machine learning methods for automatically detecting anomalous transient events such as kilonovae and peculiar supernovae, and characterising variable stars. I’ll explore the challenge of developing representative latent spaces useful for downstream machine learning tasks and present a novel causally-motivated foundation model. I’ll apply the approach to transients from the Zwicky Transient Facility (ZTF) and simulations of variable stars while discussing applications to upcoming surveys.

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Thu 12 Jun 16:00: Transient astrophysics with the Gravitational wave Optical Transient Observer (GOTO)

Tue, 03/06/2025 - 11:51
Transient astrophysics with the Gravitational wave Optical Transient Observer (GOTO)

Gravitational-wave (GW) multi-messenger astronomy holds immense promise for our understanding of the Universe, impacting studies of cosmology, the production of elements, and the final fates of stars. To date, however, only a single credible source, GW170817 , caused by the merger of two neutron stars, has been detected both in GWs and electromagnetically. I will discuss the scientific potential and challenges of observing more multi-messenger events, as motivation for the GOTO project: a UK-led transient sky survey composed of a fleet of rapidly-responding telescope arrays. The primary science driver of GOTO is scanning the sky in response to GW alerts, to search for their electromagnetic counterparts. Alongside overviewing GOTO ’s capabilities and recent multi-messenger efforts, I will present highlights from various ancillary science enabled by the array. This includes rapid localisation and characterisation of gamma-ray bursts, and discoveries of infant and extreme supernovae beyond the traditional core-collapse and thermonuclear regimes. I will also present our efforts to automate and expedite the characterisation of transients via algorithmically scheduled follow-up and citizen scientists.

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Thu 05 Jun 16:00: The Formation and Co-Evolution of Galaxies and Supermassive Black Holes

Tue, 03/06/2025 - 09:21
The Formation and Co-Evolution of Galaxies and Supermassive Black Holes

Cosmological hydrodynamical simulations are becoming increasingly realistic by incorporating a wider range of physical processes, higher spatial resolution, and larger statistical samples. Despite ongoing trade-offs between resolution and volume, recent advances now allow for simulations that resolve the multiphase interstellar medium and capture the clumpy nature of star formation in galaxies. In this context, I will present how such simulations shed light on the coupled evolution of galaxies and their central supermassive black holes. At high redshift, galaxies tend to be gas-rich, turbulent, and star-bursting, often exhibiting irregular, compact, and disturbed morphologies. As internal turbulence subsides, many systems transition into stable, rotating disc galaxies, typically once they reach stellar masses around 1e10 Msun. Simultaneously, black hole growth is tightly linked to the dynamical state of the host galaxy. In low-mass, turbulent systems, stellar feedback can suppress nuclear gas inflows, delaying black hole growth. Only when galaxies become sufficiently massive and dynamically settled can gas efficiently reach galactic centers to fuel sustained accretion. These processes also have important implications for the spin evolution of black holes or how fast they coalesce, which can reflect the varying modes of accretion and feedback across cosmic time.

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Fri 06 Jun 11:30: Exploring the End of Reionization

Mon, 02/06/2025 - 15:22
Exploring the End of Reionization

Abstract not available

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Wed 11 Jun 13:15: Neurodiversity and Communication Styles

Mon, 02/06/2025 - 14:54
Neurodiversity and Communication Styles

Dr Maria Dias, Neurodiversity Adviser at the Accessibility and Disability Resource Centre (ADRC) and St Catharine’s College, will explore how people with different neurotypes communicate in unique ways, and why understanding these differences is important for creating more inclusive and supportive environments. Whether you’re neurodivergent yourself, work with neurodivergent people, or just want to learn more, this talk is for you. There will be time for questions and open discussion at the end.

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Mon 02 Jun 16:00: Imaging and Design with Differentiable Physics Models

Mon, 02/06/2025 - 10:51
Imaging and Design with Differentiable Physics Models

The technology that underpins machine learning – differentiable programming – is poised to revolutionise astronomy, making it possible for the first time to fit very high dimensional models: hierarchical models describing many objects; the sensitivity of millions of pixels in a detector; models of images or spectra with very many free parameters; or neural networks that represent physics we cannot easily solve in closed form. It also enables fundamental information-theoretic quantities like the Fisher information to be calculated, allowing for determination and optimization of the information content of an experiment. I will discuss how we apply this to the James Webb interferometer experiment, to provide a data-driven self-calibration of the telescope’s highest resolution mode and its difficult systematics; to design the Toliman Space Telescope to do high-precision, distortion-tolerant astrometry; and give an overview of related work on interferometry, transits and AGN reverberation mapping in our group.

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Tue 10 Jun 16:00: Title to be confirmed

Sat, 31/05/2025 - 08:58
Title to be confirmed

Abstract not available

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Wed 04 Jun 13:40: GPU Accelerated Sampling and Model Comparison

Fri, 30/05/2025 - 11:43
GPU Accelerated Sampling and Model Comparison

This talk introduces a natively vectorized implementation of the Nested Sampling algorithm, enabling deployment of the entire inference process onto GPUs for massive acceleration. I will start by reviewing the benefits, and necessity, of the paradigm shift towards vectorized compute in the physical sciences. After a brief review of the how (and why) of Bayesian inference in Astronomy and Cosmology, I will then explore the nuances and challenges of taking some of the widely used inference algorithms within this community, in particular nested sampling, to the GPU accelerated frontier. Lastly I’ll present some practical benefit that this speedup can bring and comment on how this technical development can help push the boundaries of what we can achieve in the physical sciences.

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Wed 04 Jun 13:15: Geometric mixing models as a tool for investigating the ice shell of Europa

Thu, 29/05/2025 - 10:19
Geometric mixing models as a tool for investigating the ice shell of Europa

The presence of liquid water is vital to the understanding of a planetary body’s climate, geological history, and habitability. The use of ice-penetrating radar as a probe for subsurface hydrology has been demonstrated across Earth and nearby planetary bodies. Radar sounding has uncovered hundreds of subglacial lakes across the Antarctic and Greenland ice sheets, while a recent mission to Mars (MARSIS) found anomalously bright reflectances suggesting the presence of a subglacial lake at the South Polar Layered Deposits. The recently launched Europa Clipper is similarly equipped with an ice-penetrating radar instrument, REASON , which will search for evidence of liquid water on Europa as an indicator of habitability.

However, the uniqueness of reflectivity as an identifier for subglacial water bodies has recently been called into question: conductive sediments and brine inclusions in ice have been proposed as alternate hypotheses for the origin of water-like radar signals at Mars and the Devon ice cap. Conventional approaches to studying the effective permittivity of such mixtures assume an isotropic distribution; here we apply geometric mixing models to account for realistic, anisotropic brine geometries. We demonstrate how geometric mixing models can provide more exact constraints on the presence and geometric distribution of liquid water in Europa’s ice shell. We further discuss the detectability of the eutectic zone in the ice shell and its implications for its thermal structure.

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Fri 18 Jul 11:30: Title to be confirmed

Tue, 27/05/2025 - 18:13
Title to be confirmed

Abstract not available

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Wed 28 May 13:15: Inward (or outward?) migration of massive planets in protoplanetary discs

Mon, 26/05/2025 - 09:46
Inward (or outward?) migration of massive planets in protoplanetary discs

According to the classical picture, type II migration is a slow, inward motion of the planet that either follows the disc viscous evolution (disc-dominated regime) or is much slower than that (planet-dominated regime). However, over the last decade, this picture of type II migration has significantly evolved, suggesting faster migration in the disc-dominated regime and even outward migration in the planet-dominated regime. In this talk, I will present recent results exploring the planet-dominated regime via live-planet, long-term simulations of planet migration. These show the existence of a correlation between the “gap-depth parameter” K and the direction of planet migration: planets migrate outward or inward depending on whether K is above or below a critical threshold Klim. This also implies the existence of “stalling radius” where migration halts. Using these results, I will introduce a toy model that allows to predict that massive planets accumulate in a band near the stalling radius (typically between 1–10 au), offering an explanation for the observed distribution of Jupiter-like exoplanets while challenging classical models of hot Jupiter formation.

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Wed 28 May 13:40: Shamrock: SPH and more, from a laptop to Exascale.

Mon, 26/05/2025 - 09:46
Shamrock: SPH and more, from a laptop to Exascale.

We introduce Shamrock, a performance-portable framework written in C++17, targeting CPU and GPUs from any vendors using the SYCL programming standard, designed for numerical astrophysics across a wide range of hardware, from laptops to Exascale systems. Astrophysical schemes often share a common structure: a combination of neighbor searching and the numerical scheme itself. Shamrock embraces such abstractions to provide a common framework for multiple hydrodynamical schemes, namely finite elements, finite volume (with adaptive mesh refinement), and Smoothed Particle Hydrodynamics. To achieve this, at its core, Shamrock features a highly optimized, parallel tree algorithm with negligible construction overhead. This tree structure is coupled with a domain decomposition strategy that enables near-linear weak scalability across multiple GPUs. Shamrock achieves 92% weak scaling efficiency on 1024 AMD M I250x GPUs in large-scale Smoothed Particle Hydrodynamics (SPH) simulations. This corresponds to processing billions of particles per second, with tens of millions of particles handled per GPU , allowing us to perform the first SPH simulations above the billion-particle mark for protoplanetary discs.

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Fri 13 Jun 11:30: The Dynamics of Debris Disk Creation in Neutron Star Mergers

Fri, 23/05/2025 - 17:17
The Dynamics of Debris Disk Creation in Neutron Star Mergers

The detection of GW170817 /AT2017gfo inaugurated an era of multimessenger astrophysics, in which gravitational-wave and multiwavelength photon observations complement one another to provide unique insight into astrophysical systems. A broad theoretical consensus exists, in which the photon phenomenology of neutron star mergers largely rests upon the evolution of the small amount of matter left on bound orbits around the black hole or massive neutron star remaining after the merger. Because this accretion disk is far from inflow equilibrium, its subsequent evolution depends very strongly on its initial state, yet very little is known about how this state is determined. Using both snapshot and tracer particle data from a numerical relativity/MHD simulation of an equal-mass neutron star merger that collapses to a black hole, we show how gravitational forces arising in a nonaxisymmetric, dynamical spacetime supplement hydrodynamical effects in shaping the initial structure of the bound debris disk. The work done by hydrodynamical forces is ∼10 times greater than that due to time-dependent gravity. Although gravitational torques prior to remnant relaxation are an order of magnitude larger than hydrodynamical torques, their intrinsic sign symmetry leads to strong cancellation; as a result, hydrodynamical and gravitational torques have a comparable effect. We also show that the debris disk’s initial specific angular momentum distribution is sharply peaked at roughly the specific angular momentum of the merged neutron star’s outer layers, a few r g c, and identify the regulating mechanism.

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Thu 29 May 16:00: Latest results building upon slitless spectroscopic surveys with JWST

Fri, 23/05/2025 - 12:12
Latest results building upon slitless spectroscopic surveys with JWST

I will present results on the properties of faint galaxies and AGN in the early Universe, building upon samples identified using Wide Field Slitless Spectroscopy with NIR Cam on the James Webb Space Telescope (JWST). This mode effectively turns JWST into an efficient redshift machine ideal to map out galaxy over-density. In my talk, I will focus on two topics: 1) The impact of galaxies and AGN on the reionization of the Universe, directly measured by mapping out the correlation between galaxies and ionized regions with quasar and galaxy transmission spectroscopy, and 2) The nature of broad Hα line-selected AGN (the so-called Little Red Dots) that JWST has uncovered in the first few Gyr, including new results based on the deep NIR Cam grism spectroscopy of their large-scale environments, deep high resolution spectroscopy unveiling the prevalence of dense absorbing gas and resolved Lyman-alpha mapping of the circumgalactic medium with VLT /MUSE. Finally, I will synthesize what these observations are learning us in the context of galaxy – SMBH co-evolution, SMBH formation and their role in cosmic reionization.

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Tue 03 Jun 13:00: Hints of Planet Formation Signatures in a large-cavity disk in Upper Scorpius

Fri, 23/05/2025 - 11:17
Hints of Planet Formation Signatures in a large-cavity disk in Upper Scorpius

Detecting signatures of planet formation in protoplanetary disks is essential for understanding how and where planets form. In this talk, I will summarise the various fingerprints of planets on the distribution of gas and dust solids in protoplanetary disk, and present Dust and gas observations of the disk around 2MASS J16120668 -301027, studied as part of the ALMA Large Program ‘AGE-PRO: ALMA Survey Of Gas Evolution in Protoplanetary Disks’, where several indicator of planet formation were recently identified in dust dust continuum emission and for molecular lines

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Thu 19 Jun 16:00: Unveiling the nature of dark matter with small-scale cosmic structure

Fri, 23/05/2025 - 00:04
Unveiling the nature of dark matter with small-scale cosmic structure

Cosmological and astrophysical observations provide clear evidence for the existence of dark matter and have begun to map its distribution across vast cosmic volumes, yet key questions about its mass and interaction properties remain unanswered. Clues may lie in measurements that probe structure formation on the smallest scales—including dwarf galaxies, strong gravitational lenses, and stellar streams. These observations are already constraining aspects of the microphysical nature of dark matter, including its free-streaming behavior, decay lifetime, self-interactions, and possible interactions with the Standard Model. The upcoming generation of wide-field imaging surveys—including Euclid, the Vera C. Rubin Observatory, and the Roman Space Telescope—combined with spectroscopic surveys such as DESI and the new Via Project, will accelerate our ability to probe this physics. These efforts may detect, for the first time, dark matter halos below the threshold for star formation, directly testing a fundamental prediction of the standard cosmological model and offering the possibility of uncovering definitive astrophysical signatures of dark matter’s particle properties.

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