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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 20 min ago

Wed 01 May 15:00: The next-generation Event Horizon Telescope: from Still Images to Video.

Fri, 26/04/2024 - 11:00
The next-generation Event Horizon Telescope: from Still Images to Video.

The next-generation Event Horizon Telescope (ngEHT) is a transformative upgrade to the EHT that will realize black hole “cinema”: real-time and time-lapse movies of supermassive black holes on event horizon scales. These movies will resolve complex structure and dynamics on Schwarzschild radius dimensions, bringing into focus not just the persistent strong-field gravity features predicted by General Relativity (GR), but details of active accretion and relativistic jet launching that drive large scale structure in the Universe. This effort builds upon recent results by the Event Horizon Telescope (EHT): the first image of M87 ’s supermassive black hole and its magnetic field structure, as well as resolved images of SgrA*, the central black hole at the heart of the Milky Way. These images are scientifically rich, and show that evolution of the EHT to a more capable array can address even deeper questions across physics and astronomy. The central concept behind the ngEHT is that the addition of modest-diameter dishes at new geographic locations and multi-color observations over a range of frequencies will enable the next revolution in horizon-resolved black hole studies. This talk will cover the ngEHT technical plans and scientific goals.

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Tue 25 Jun 11:30: TBC

Thu, 25/04/2024 - 11:36
TBC

Details to be confirmed

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Tue 25 Jun 11:30: TBC

Thu, 25/04/2024 - 11:35
TBC

Details to be confirmed

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Thu 13 Jun 11:30: Title to be confirmed

Wed, 24/04/2024 - 10:24
Title to be confirmed

Abstract not available

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Wed 24 Apr 10:00: Neural ratio estimation: the future of supernova cosmology?

Mon, 22/04/2024 - 15:53
Neural ratio estimation: the future of supernova cosmology?

Simulation-based inference (SBI) has the potential to revolutionise how we do supernova cosmology and let us incorporate arbitrarily complex effects within a Bayesian model. I will present recent work which sought to validate neural ratio estimation (NRE) by comparing NRE -derived posteriors on supernova properties to those obtained with a likelihood-based MCMC approach for the same data, and then discuss how NRE and SBI in general provide a pathway towards a model extending all the way from type Ia supernova light curves to cosmological parameters as part of a single analysis.

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Tue 30 Apr 13:00: Stellar activity mitigation in radial velocity measurements

Fri, 19/04/2024 - 13:58
Stellar activity mitigation in radial velocity measurements

Over the past decades, the radial velocity (RV) community has made tremendous leaps forward in detecting and characterising ever smaller and lighter exoplanets. This trend has been interrupted in recent years, as planetary RV signals below 1 m/s are drowned out by the stars’ activity. The detection of Earth analogues producing an RV effect of about 10 cm/s is therefore currently out of reach. Several avenues are being explored to restore the trend towards the detection of increasingly less massive planets. These include improvements in (1) instruments, (2) observing strategies, (3) RV extraction techniques, (4) stellar activity monitoring, and (5) stellar activity modelling. In this talk, I will focus on points (4), and (5). I will provide an overview of stellar activity mitigation techniques and show how a proxy for stellar magnetic activity induced RV variations can be extracted from intensity spectra in the visible wavelength range, providing an independent estimate of the evolution of the magnetic field.

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Tue 07 May 11:30: The recently discovered black holes in wide binaries by Gaia astrometry

Fri, 19/04/2024 - 13:30
The recently discovered black holes in wide binaries by Gaia astrometry

I will discuss the recent discovery of the three black holes (BH) by Gaia astrometry, concentrating on BH3 , with a mass of 33 M_solar, which is orbited by a very metal poor giant in an orbit of 12 years. The BH in the Gaia BH3 system is more massive than any other Galactic stellar-origin BH known. The Galactic orbit of the system and its metallicity indicate that it probably belongs to the ED-2 stream, which likely originated from a globular cluster that was disrupted by the Milky Way.

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Fri 26 Apr 11:30: The Via Project: Mapping the invisible Galactic halo

Wed, 17/04/2024 - 23:35
The Via Project: Mapping the invisible Galactic halo

Abstract not available

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Fri 26 Apr 11:30: Title to be confirmed

Wed, 17/04/2024 - 15:51
Title to be confirmed

Abstract not available

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Fri 10 May 11:30: Title to be confirmed

Wed, 17/04/2024 - 08:42
Title to be confirmed

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Tue 30 Apr 13:00: Title to be confirmed

Sun, 14/04/2024 - 12:47
Title to be confirmed

Abstract not available

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Tue 28 May 13:00: Title to be confirmed

Sun, 14/04/2024 - 12:44
Title to be confirmed

Abstract not available

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Tue 21 May 13:00: Title to be confirmed

Sun, 14/04/2024 - 12:44
Title to be confirmed

Abstract not available

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Tue 23 Apr 13:00: The physical mechanism of the streaming instability, and whether it works in vortices

Sun, 14/04/2024 - 12:41
The physical mechanism of the streaming instability, and whether it works in vortices

A major hurdle in planet formation theory is that we do not understand how small pebbles congregate into big planetesimals. A promising way to overcome this metre-scale barrier involves a fluid dynamics phenomenon called the streaming instability (SI). It concentrates the pebbles into clumps that are dense enough to collapse gravitationally, thereby forming planetesimals.

Unfortunately, the mechanism responsible for the onset of the instability remains mysterious. This makes it hard to evaluate the robustness of the instability, or to understand how it saturates. It has recently been shown that the SI is a Resonant Drag Instability (RDI) involving inertial waves. In the first part of this talk, I build on this insight to produce a clear physical picture of how the SI develops.

Another problem is that the SI can only devellop in regions containing a high density of similar-sized pebbles. Those conditions are met in large-scale vortices, but no one knows if the SI can feed on vorticial flows. Indeed, any instability can only devellop in specific flows, and a priori the SI is tailored to Keplerian disc flows, not vortex flows. I answer this question in the second part of the talk. To do so, I develop a simple pen-and-paper model of a dust-laden vortex in a protoplanetary disc. I find that if the vortex is weak and anticyclonic, dust drifts towards its centre. I then build a vortex analog of the shearing box to analyse the local linear stability of my dusty vortex. I find that the dust’s drift powers an instability which closely resembles the SI. This result strengthens the case for vortex-induced planetesimal formation.

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Thu 02 May 16:00: Experimental Studies of Black Holes: Status & Prospects

Fri, 12/04/2024 - 11:45
Experimental Studies of Black Holes: Status & Prospects

More than a century ago, Albert Einstein presented his general theory of gravitation. One of the predictions of this theory is that not only particles and objects with mass, but also the quanta of light, photons, are tied to the curvature of space-time, and thus to gravity. There must be a critical mass density, above which photons cannot escape. These are black holes. It took fifty years before possible candidate objects were identified by observational astronomy. Another fifty years have passed, until we finally can present detailed and credible experimental evidence that black holes of 10 to 10^10 times the mass of the Sun exist in the Universe. Three very different experimental techniques have enabled these critical experimental breakthroughs. It has become possible to investigate the space-time structure in the vicinity of the event horizons of black holes. I will summarize these interferometric techniques, and discuss the spectacular recent improvements achieved with all three techniques. In conclusion, I will sketch where the path of exploration and inquiry may lead to in the next decades.

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Fri 19 Apr 11:30: Probing the epoch of galaxy assembly with MUSE

Thu, 11/04/2024 - 13:14
Probing the epoch of galaxy assembly with MUSE

Abstract not available

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Fri 31 May 11:30: Title to be confirmed

Tue, 09/04/2024 - 17:11
Title to be confirmed

Abstract not available

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Wed 22 May 11:30: Hierarchical star cluster assembly boosts intermediate-mass black hole formation

Mon, 08/04/2024 - 09:08
Hierarchical star cluster assembly boosts intermediate-mass black hole formation

Observations and high-resolution hydrodynamical simulations indicate that massive star clusters assemble hierarchically from sub-clusters with a universal power-law cluster mass function. We study the consequences of such assembly for the formation of intermediate-mass black holes (IMBHs) and massive black hole (MBH) seeds at low metallicities (1% of the solar value) with our updated direct N-body code BIFROST in simulations up to N = 2.35 million stars. The GPU -accelerated code BIFROST is based on the hierarchical fourth-order forward integrator. Few-body systems are treated using secular and regularized techniques including post-Newtonian equations of motion up to order PN3 .5 and gravitational-wave recoil kicks for merging BHs. Stellar evolution is provided by the fast population synthesis code SEVN . IMBHs with masses up to 2200 solar masses form rapidly mainly via the collapse of very massive stars (VMSs) assembled through repeated collisions of massive stars followed by growth through tidal disruption events (TDEs) and BH mergers. Later the IMB Hs form subsystems resulting in gravitational-wave BH-BH, IMBH -BH and IMBH -IMBH mergers with a 1000 solar mass gravitational-wave detection being the observable prediction. Our simulations indicate that the hierarchical formation of massive star clusters in metal poor environments naturally results in formation of potential seeds for supermassive black holes.

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Thu 16 May 16:00: Inside Astronomically Realistic Black Holes

Fri, 05/04/2024 - 23:35
Inside Astronomically Realistic Black Holes

I will use a real-time general relativistic Black Hole Flight Similator to show what really happens inside astronomically realistic black holes. The inner horizon of a rotating black hole is the most violent place in the Universe, easily reaching and surpassing energy densities attained in the Big Bang. What does Nature do at this extraordinary place?

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Tue 07 May 11:30: KICC Special Seminar (Title TBC)

Fri, 05/04/2024 - 13:29
KICC Special Seminar (Title TBC)

Abstract not available

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