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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: 1 hour 37 min ago

Fri 06 Jun 11:30: Title to be confirmed

Fri, 21/03/2025 - 17:16
Title to be confirmed

Abstract not available

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Fri 30 May 11:30: Title to be confirmed

Thu, 20/03/2025 - 09:05
Title to be confirmed

Abstract not available

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Fri 21 Mar 11:30: Unveiling the Intrinsic Mass Step of Type Ia Supernovae

Mon, 17/03/2025 - 15:45
Unveiling the Intrinsic Mass Step of Type Ia Supernovae

It has long been established that the properties of type Ia supernovae (SNe Ia) depend on their local environment, even after typical standardisation methods. This is typically referred to as the mass step, where SNe Ia in high-mass galaxies are on average brighter than their low-mass counterparts post-standardisation, although trends have been established with other environmental properties including colour, specific star formation rate and distance from the centre of the galaxy. There has been ongoing debate in the field about whether these differences are intrinsic or just the result of extrinsic effects i.e. dust. I will present recent analysis of the environmental dependence of SNe Ia which have found an intrinsic contribution to the mass step, with particularly strong differences around the i-band secondary maximum. These results demonstrate that there are intrinsic differences between SNe Ia in different environments and raise an interesting question about what is driving these results; understanding this finding can help reveal the underlying physical cause of the environmental dependence of SNe Ia.

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Wed 19 Mar 13:40: Perturber-disc interaction: Can we see the unseen?

Mon, 17/03/2025 - 10:52
Perturber-disc interaction: Can we see the unseen?

Protoplanetary discs are the place in which planets form and evolve, and the reservoir from which protostar accrete material. The presence of a perturber whether a planet or a stellar companion and its interaction with the parental disc play a crucial role in shaping the dynamics and evolution of the system, generating substructures such as gaps, rings and asymmetries routinely observed with different tracers in discs (large mm dust and gas with ALMA , small micrometric dust with VLT ).

However, characterizing these systems remains challenging: the only two planetary companions unambiguously detected, PDS70b and c, lie in a wide and open cavity of the same object, and once the perturber is a star, massive and wide enough to be detected, characterize the binary orbit is challenging due to the timescales at play.

In this talk, I will show new results to address and mitigate these issues. Firstly, I will show new results from the astrometry and the hydrodynamical models of GG Tau A, a multiple stellar system where the orbits of the stars is still not fully constrained. Then, I will discuss how the advent of the Extremely Large Telescope (ELT), with its first light imager MICADO /MORFEO, will revolutionize the field, providing high angular resolution images that will allow us to detect embedded protoplanets and small-scales substructures.

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Wed 19 Mar 13:15: Constraining mixed dark matter models with the high-redshift Lyman-α forest

Fri, 14/03/2025 - 16:47
Constraining mixed dark matter models with the high-redshift Lyman-α forest

In the standard cosmological model, cold dark matter gives rise to small-scale structure problems which Warm Dark Matter (WDM) in the keV range may address. Previous studies have narrowed the mass range for WDM , but further testing is increasingly challenging due to resolution limits of current spectrographs. Given the lack of success in laboratory dark matter searches, an intriguing alternative has recently re-emerged—a mixed dark matter scenario that combines cold and warm components, known as Cold+Warm Dark Matter (CWDM). In this framework, structure formation is influenced by the free-streaming of the warm component at the small scales probed by the Lyman-α forest, requiring hydrodynamical simulations to account for non-linear structure evolution and gas dynamics.

This presentation focuses on updated constraints on CWDM derived from high resolution and high-redshift (z=4.2−5.0) spectra from UVES and HIRES spectrographs. We use the 1D flux power spectrum to compare simulated Lyman-α forest to observational data in a Bayesian inference framework. The grid of simulations spans a high-dimensional parameter space, which we efficiently sample by implementing a neural network emulator at the likelihood level.

Beyond 1D clustering statistics, these allowed mixed dark matter models can accommodate small-scale deviations in the high-k regime of the matter power spectrum, potentially alleviating the S8 tension.

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Wed 12 Mar 13:40: IoA neurodiversity survey insights and next steps

Wed, 12/03/2025 - 11:46
IoA neurodiversity survey insights and next steps

We’ll explore the key findings from the recent IoA staff neurodiversity survey. We’ll celebrate the positive experiences shared by participants and shine a light on some of the challenges. The session will address some comments raised in the survey, while also outlining the focus group’s priorities as we move forward.

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Wed 12 Mar 13:15: Accessibility in Astronomy: HTML papers on arXiv, alternative text, and beyond

Wed, 12/03/2025 - 11:45
Accessibility in Astronomy: HTML papers on arXiv, alternative text, and beyond

Astronomy is a heavily visual science. Outreach and education typically rely on beautiful images of the sky, and the communication of research findings in papers and talks revolves around figures. These visual media, while beautiful and effective for many audiences, have historically excluded blind and low vision people from engaging with astronomy. How can we work together towards science that is more inclusive of blind people and people with disabilities more broadly? In this talk, I will discuss accessibility in astronomy, particularly for the blind and low vision community. Topics will include the new HTML paper format on arXiv, writing alternative (alt) text for figures, and some best practices for organizing and attending conferences. Some general background on disability and assistive technology will also be discussed.

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Tue 18 Mar 13:00: An Early Heavy Bombardment of the Inner Solar System

Tue, 11/03/2025 - 14:03
An Early Heavy Bombardment of the Inner Solar System

The orbital architecture of planets in the Solar System is thought to have been set shortly after its birth. However, ancient asteroid families are highly dispersed, suggesting that perhaps the Solar System remained chaotic until later in its history. Testing this possibility requires precise dating of the collisions that should have generated such families, but planetary surfaces record little to no information from this time. The meteorite record of asteroid collisions represents a separate and more complete archive of Solar System evolution. In this project, we leveraged recent methodological advances to build an extensive record of in-situ meteorite apatite U-Pb ages, sensitive to collisions that induce parent body break-up events. Most asteroid collisions in our record occurred 4480 +/- 20 million years ago. Only highly dispersed asteroid families are potentially co-eval with our U-Pb ages, demonstrating that strong perturbations modifying the orbital eccentricities and inclinations of asteroids were still operating at 4480 Ma. This is unexpected in scenarios where the planets completed their growth and acquired their current orbits in a few Myr within the dispersal of the protoplanetary disk. Our work provides unique evidence that the asteroid belt was still in a state of dynamical chaos 80 Myr after its formation.

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Tue 11 Mar 13:00: Greedy icy planets, or How Uranus and Neptune enrich their atmospheres in carbon by core accretion in the debris disc phase

Thu, 06/03/2025 - 09:59
Greedy icy planets, or How Uranus and Neptune enrich their atmospheres in carbon by core accretion in the debris disc phase

Observations of gas in exo-Kuiper belts (mostly CO) suggest it may be common in young planetary systems, potentially reshaping our understanding of the Solar System’s youth. Uranus and Neptune’s high atmospheric C/H ratios (60–80× protosolar) could trace late accretion of carbon-rich gas from a primordial Kuiper belt. We model gas release and viscous evolution in a Solar System-analog belt, quantifying gas capture by the ice giants. Using a disk model with varied initial masses (up to 50 M⊕), viscosities, and accretion efficiencies, we simulate CO release and planetary enrichment. Results show a massive belt (∼50 M⊕, similar to that considered in e.g. the Nice model) can supply sufficient CO via late accretion to explain observed C/H values. While solid accretion during formation contributes to carbon enrichment, we find that an additional late accretion may be needed to explain the very high super solar values, which aligns with gas capture from a young, gaseous Kuiper belt. This mechanism may be universal, influencing metallicity in exoplanetary giants, with observational implications for sub-Jupiter exoplanets. Our findings support a once-gas-rich Kuiper belt as a key driver of ice giant atmospheric evolution.

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Mon 24 Mar 16:00: Shared Stochastic Gaussian Process Latent Variable Models: A Multi-modal Generative Model for Quasar Spectra

Wed, 05/03/2025 - 23:18
Shared Stochastic Gaussian Process Latent Variable Models: A Multi-modal Generative Model for Quasar Spectra

This work proposes a scalable probabilistic latent variable model based on Gaussian processes (Lawrence, 2004) in the context of multiple observation spaces. We focus on an application in astrophysics where it is typical for data sets to contain both observed spectral features as well as scientific properties of astrophysical objects such as galaxies or exoplanets. In our application, we study the spectra of very luminous galaxies known as quasars, and their properties, such as the mass of their central supermassive black hole, their accretion rate and their luminosity, and hence, there can be multiple observation spaces. A single data point is then characterised by different classes of observations, which may have different likelihoods. Our proposed model extends the baseline stochastic variational Gaussian process latent variable model (GPLVM) (Lalchand et al., 2022) to this setting, proposing a seamless generative model where the quasar spectra and scientific labels can be generated simultaneously when modelled with a shared latent space acting as input to different sets of Gaussian process decoders, one for each observation space. In addition, this framework allows training in the missing data setting where a large number of dimensions per data point may be unknown or unobserved. We demonstrate high-fidelity reconstructions of the spectra and the scientific labels during test-time inference and briefly discuss the scientific interpretations of the results along with the significance of such a generative model.

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Fri 14 Mar 11:30: Baryonic feedback: How extreme is too extreme?

Wed, 05/03/2025 - 11:04
Baryonic feedback: How extreme is too extreme?

Abstract not available

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Thu 06 Mar 10:00: Bayesian Identification of Global 21cm Signal Depth Origin

Wed, 05/03/2025 - 10:17
Bayesian Identification of Global 21cm Signal Depth Origin

Theoretical models have suggested that the depth of the Global 21cm signal could be enhanced beyond that of standard astrophysics by the presence of excess radio backgrounds or excess cooling of the intergalactic medium. However, these two effects will manifest similarly in the 21cm signal itself, making them hard to distinguish from the signal alone. In this talk, I will discuss a potential method for telling these two cases apart via physical modelling of the foreground components, in order to identify the presence or absence of an excess background component in those foregrounds.

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Thu 03 Apr 10:00: Title to be confirmed

Tue, 04/03/2025 - 13:32
Title to be confirmed

Abstract not available

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Thu 20 Mar 10:00: GINAN Update

Tue, 04/03/2025 - 13:31
GINAN Update

Abstract not available

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Fri 23 May 11:30: Title to be confirmed

Fri, 28/02/2025 - 11:05
Title to be confirmed

Abstract not available

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Fri 07 Mar 11:30: Simulating supermassive black holes: from event horizon to cosmic web and back again

Thu, 27/02/2025 - 13:38
Simulating supermassive black holes: from event horizon to cosmic web and back again

Abstract not available

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Tue 06 May 11:30: The Milky Way and the Ancient Egyptian Goddess of the Sky

Fri, 21/02/2025 - 09:08
The Milky Way and the Ancient Egyptian Goddess of the Sky

The ancient Egyptians left us some of the earliest records of the night sky, where they noted the Sun, Moon, planets, and several constellations. Many of these objects are associated with – or personified by – certain gods (such as Re and the Sun). Yet how the Egyptians conceptualized the Milky Way remains unclear. In my talk, I will focus on the popular suggestion that the Milky Way was a manifestation of Nut, the Egyptian goddess of the sky. I have tested this theory by combining astronomical simulations of the Egyptian night sky, readings of ancient Egyptian religious texts (the Pyramid Texts, Coffin Texts, and the Book of Nut), ancient Egyptian material culture (coffins, funerary papyri, and tomb murals), and anthropological studies of Milky Way creation stories from around the world. I will show how Nut’s depictions changed over the course of Egyptian history and present the first visual evidence for the Milky Way in ancient Egyptian art. I will conclude by arguing that the Milky Way was not a manifestation of Nut but one more astronomical phenomenon that graced her body in her role as the goddess of the sky.

Or Graur is an associate professor of astrophysics at the University of Portsmouth’s Institute of Cosmology and Gravitation. Alongside his observational studies of supernovae and tidal disruption events, Or studies the multicultural mythology of the Milky Way. In this talk, he will present the results of three papers he has written on the subject of the ancient Egyptian Milky Way.

If you have a question about this talk please contact: or.graur@port.ac.uk

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Fri 13 Jun 11:30: Title to be confirmed

Wed, 19/02/2025 - 10:08
Title to be confirmed

Abstract not available

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Tue 11 Mar 09:00: CamGW: Surveying the range of gravitational-wave science in Cambridge (Kavli Science Focus Meeting)

Mon, 17/02/2025 - 10:33
CamGW: Surveying the range of gravitational-wave science in Cambridge (Kavli Science Focus Meeting)

Abstract not available

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Fri 16 May 11:30: Title to be confirmed

Sun, 16/02/2025 - 10:49
Title to be confirmed

Abstract not available

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